1
(Ephemeroptera:
Heptageniidae)
Stenacron 2020
Stenacron
Stenacron
Mayflies
2020
Mack A Beacon
Larvae and Adults
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Back story
I have had an interest in mayflies from about the age of
7 in fly fishing. The book Hatches II by Al Caucci,
Bob Nastasi with their excellent book and photographs.
Really planted a seed, as it does for most.
In 1987 at Lyman Run PA I found a heterotarsale on the
roof of my car. Upon returning home from the USA 2009
I started collecting what I thought were Stenonema
according to their book. This is where it started because
my adults were free of black marks and theirs was not.
The facts they were so different it made me want to know more.
In their selected bibliographies there were two books I
had to have. The taxonomy and Ecology of Stenonema Mayflies,
and the Biology of a Mayfly. While starting this project in
2010 I accidentally reared a female heterotarsale she sat
looking at me even crawling up my arm. She molted to a
Spinner and stayed till she died. So most of the time from
2010 till 2020 I have been working on this poor forgotten
Genus.
Mack A Beacon
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The
Stenonema Rangers
Of
Ontario
Fighting for clean waters
Stenonema Rangers are Mack A Beacon & Benjamin R Beacon
Text and illustrations copyrighted to
Mack A Beacon 2017
©
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Who is Who?
When put in the right basic size perspective you can see why
they are so hard to tell apart, by the time you are done with
this book you will see how different they really are, even these
samples that are larger than life by 2X the real size.
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Biographies
Thomas Say (June 6, 1787 – October 10, 1834),
U.S. self-taught naturalist.
New Harmony (Indiana), 10 October 1834)
For true interpunctatum Say 1839.
Thomas Say 1817, public domain
Artist
Wilson Peale (1818)
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The histories of somethings are very endearing and very
intriguing. What I find most interesting is how we know a lot of
information on some people and times frames, and little on
others. Without the complete writings of Thomas Say I suspect
little would be know of him. Although Thomas Say died in 1834,
some of his work was not published. It is unclear to me whom
erected the species concept interpunctatum Say in 1839 after his
death. I have not yet read the book The Complete Writings of
Thomas Say 1853 so I cannot say who erected interpunctatum on
his behalf. It is very likely that in his notes and samples he
had collected and wrote about it, but had not created the
species status officially.
He was born in Philadelphia into a prominent Quaker family. As
a boy, Say often visited the family garden, where he frequently
collected
butterfly
and
beetle
specimens.
A
self-taught
naturalist, Say helped found the Academy of Natural Sciences of
Philadelphia. He continued collecting and writing for the
Academy till his death of Tuberculosis.
In 1935 the Bible of Mayflies was written, it would go onto
become the greatest book very written on the subject. Here is an
inside view of one of my copies. It is actually a very rare
version; it is a [first-first-edition]. The first 200 copies
where setup prototypes of sorts and lacked the white page to the
left with the colored Mayfly plate, and more important the text
was tilted to the left for the first 23 pages. This version in
mint condition signed by all three authors in 1937 sold at
auction for more than $4000 USD in the 2000’s.
Now here is a standard 1935 first edition even the paper is
different.
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The senior author and the books concept was Professor James G
Needham’s. The other two junior authors are Dr Jay R Traver, and
Dr Yin-Chi-Hsu. I would like to spend some time here on Dr
Traver. First thing is who Dr Traver was. With a name like Jay
the first thought is that must be a man. I thought so for a
period of time. It was when I was reading deep in to discussions
on a species in Lewis 1974 where I read “she”.
Dr Traver is in fact a woman. As a matter of fact there are many
very important female entomologists like Anna H Morgan. Velma
Knox-Mayo. It should also be noted that a lot of the
illustrations for the Biology of Mayflies were illustrated by Dr
Velma Knox-Mayo. It was actually her work that inspired mine,
page 137 and 138, and most importantly page 131 for the
Stenacron frontale larva, and her proximum abdomen figure 93.
To be quite honest I am not that much of a reader but I am now.
I have never truly read an entire book. It never interests me
that much. But there is one author that I really took a shine to
and have read nearly very thing they wrote, and that is Jay R
Traver. There is something about how she wrote that speaks to
me. I can’t explain it like I knew her at one time. When I read
her work it is like she is talking to me in person. So because
she did all the systematics for the book and wrote all the
species descriptions she needs to be talked about. I recently
received from the Cornell University Archival Department a
complete file on her and her carrier post cards and all. Very
little is known about her and I have just enough to piece
together a profile of her. So let’s start with the principles of
my book!
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“Putting a face to a name”
Miss Jay R Traver in 1918
Jay R Traver 1894 – 1974
In the newspaper article from the Springfield Union, Springfield
Mass Friday Sept 6th 1974, she died on the 5th in the Cooley
Dickerson Hospital at the age of 80 from cancer.
Let’s start at the beginning. She was born August 2nd 1894 in
Willoughby Ohio at the Willoughby Hospital. She grew up on 112
River St in Willoughby and used that address often throughout
her life until moving to Massachusetts. Here is a photo of the
house at 112 River St from the archive. I imagine the tree in
the front was smaller back then. There is no date for the photo.
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Somewhere between 1935 and 1952 the city Willoughby made changes
to the addresses on river St. If you google search these two
address they are the same. 112 River St and 4566 River St is the
same house. What is ironic is there is a river right across the
street called Chagrin. I suspect her interest in mayflies
started very early as they would have been drawn to the outside
lamp of her house. Candidum, gildersleevei and conjunctum are
from that river near her house.
Somethings are unclear like how did she get the name Jay. I have
no birth certificate to indicate another name and it appears
throughout her whole life. Records show her father died 3 weeks
before her birth, and her mother named her after her father. Her
mother, Mrs. Mable M Traver is present till after 1952.
We know that she attended Willoughby high school and graduated
in 1912. There are no recorded of what she did between then and
entering Cornell in 1914 at the age of 20. All records indicate
she entered Cornell under the classes of Arts General, and
Sciences, and on July 16th 1918 got her BA, Dr Traver showed an
obvious interest in teaching right away.
While doing her Masters 1918-1919 she was also acting as an
assistant of biology in an official capacity. November 1st 1919
received her Master’s diploma and likely stayed at Cornell till
June 1920.
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Although the length of time is not indicated she did spend a
very short period of time at 430 West 188th St New York City in
upper Manhattan. With it being in her alumni records it must
have occurred between Cornell 1919 and her first job.
She took her first official job from her Cornell education in
1920 as The Supervisor of Natural History Study for the
Wilmington Delaware public school system. From what I read she
did not work in a school per say. The only thing very clear is
she was moving around a lot in Wilmington there are four
different addresses inside a three year job position ending in
1923.
In 1924-1925 came a job that was a big stepping stone. She took
the official position of Head of the Biology Department of
Shorter College in Rome Georgia. This position certainly set her
up for the job and location that would be life changing.
From 1924 through 1930 came the job that defined her. It was
actually more than the job it was the location. The new job she
took was Assistant Professor of Biology at Woman’s-College
University of North Carolina in Greensboro.
If we read deep many new species concept of hers are located
very close by like affine. The amount of personal collection and
study must have been very high because this lead to her
published thesis “The mayflies of North Carolina” in 1931 and
she received her PhD on September 30th 1931.
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You can contact the author
Mack A Beacon if there is
Anything I can help you with.
Stenacron.books@gmail.com
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Mack A Beacon
Stenacron
1839 - 2020
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INTRODUCTION
Welcome to the secret world of
Stenacron mayflies
This is an advanced guide that will enable you to identify all
the different forms in the genus in the Larvae & adult stages.
With the current taxonomic conditions of the genus we will go to
form, rather than species. Once form is identified, you are
encouraged to go to Mayfly Central on the internet to locate the
current species status. Using this guide is simple! First
compare
the
collected
larvae
or
adult
to
the
general
illustrations. Second look up that form and stage in the
description section to make a confident identification. Third in
order to verify your findings, dissection of the mouthparts of
the larvae, and male genitals and comparing them to the genital
illustrations provided in this guide is critical also to the
characteristic feature table.
Acknowledgements
I would like to take a moment express my gratitude to some
special people. First I wish to sincerely thank Dr Jeff Webb for
his great advice and encouragement with the creation of this
guide, and the entire study project. I wish to thank Dr Luke
Jacobus for excellent advice and helping create these digital
files and making them available. I wish to thank Dr N J Kluge
for my online education with classifications. I also wish to
thank both Bill Christmas and Don McGregor for all the years of
fly fishing and for what they taught me. I would like to thank
my mother for being such a great proof reader, and supporter of
all of my endeavors. This book dedicated to the memory of Don
McGregor of the “Hackle House”. I am a much fuller and richer
man by having had his friendship throughout the years.
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Table of contents larvae
Who is Who? …………………………………………………………………………………………………… 4
Biographies……………………………………………………………………………………………………… 5
Introduction…………………………………………………………………………………………………… 13
Acknowledgements………………………………………………………………………………………… 13
Table of contents……………………………………………………………………………………… 14
Classification……………………………………………………………………………………………… 16
Concepts and goals…………………………………………………………………………………… 17
Preface………………………………………………………………………………………………………………… 20
Characteristics of the larva………………………………………………………… 20
Valid species list 2020……………………………………………………………………… 21
Life cycle………………………………………………………………………………………………………… 22
Collecting larva………………………………………………………………………………………… 22
Rearing larva………………………………………………………………………………………………… 23
Geographical distribution………………………………………………………………… 23
Historical outline…………………………………………………………………………………… 24
Transcending maculation……………………………………………………………………… 26
Male and female larva identification…………………………………… 31
Hatching periods………………………………………………………………………………………… 32
Sorting larva………………………………………………………………………………………………… 35
Behavior and ecology……………………………………………………………………………… 39
The Leopard larva……………………………………………………………………………………… 45
Range and distribution………………………………………………………………………… 50
Biodiversity…………………………………………………………………………………………………… 56
Anatomy of Stenacron larva……………………………………………………………… 73
Microscope photo plates……………………………………………………………………… 116
Photo plates…………………………………………………………………………………………………… 133
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Pale spots in front of median ocelli………………………………… 147
Head capsule illustrations…………………………………………………………… 149
Side view of full larva…………………………………………………………………… 151
General top view full illustrations…………………………………… 152
Abdomen view illustrations…………………………………………………………… 155
Master labrum blueprints………………………………………………………………… 164
Comparative discussions…………………………………………………………………… 168
Larvae couplets………………………………………………………………………………………… 194
Complete descriptions………………………………………………………………………… 197
Affine………………………………………………………………………………… 196
Areion……………………………………larva never collected
Canadense………………………………………………………………………… 200
Candidum…………………………………………………………………………… 204
Carolina…………………………………………………………………………… 208
Conjunctum……………………………………………………………………… 211
Frontale…………………………………………………………………………… 221
Floridense……………………………………………………………………… 224
Gildersleevei……………………………………………………………… 226
Heterotarsale……………………………………………………………… 229
Interpunctatum Say………………………………………………… 233
Majus…………………………………………………………………………………… 237
Minnetonka……………………………………………………………………… 240
Ohioense…………………………………………………………………………… 242
Pallidum…………………………………………………………………………… 249
Proximum…………………………………………………………………………… 251
Table of features and keys……………………………………………………………… 256-263
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Classification
(Ephemeroptera:Heptageniidae)
Stenacron
Common names
Male; light Cahill
Female; Salmon spinners
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Concept and Goals
So just what is the concept of this book and what goals did we
set out to achieve. The very first thing one must understand
this book was developed with usage as the primary function. A
book that a 4 years old child can use to the world’s leading
Taxonomists with revisionary and revolutionary concepts.
“A picture is worth thousand words”
That is the concept every form in this genus was treated equal.
Every illustration, except the labrums, anatomy, and genitals
were colored in on printed master templates. This way every
illustration would reflect the same except maculation and some
fine details. Supreme illustrations have a great advantage to
pictures; there is no focal, background, or angle issues.
We were also able to put a face to a name in all stages. This
book puts an enormous effort into the larva. For the first time
showing them side by side. This genus has been without any doubt
one of the most difficult in history. The level of accuracy in
the details of this book is mind blowing. Thousands of samples,
studied in great detail.
The goal was to revolutionize bug books by making them
scientifically correct but simple enough for any education
level. Because these are not designed to be scientific manuals.
Another goal was how to approach a truly never ending revolution
of taxonomic revisions.
As soon a one species becomes a synonym of another species both
can lose their original clarity. The greatest example is Spieth
1947 synonymizing ohioense to canadense. By doing this it
changed the description of canadense and we lost clear sight of
ohioense, but more important we lost the original concept of the
species canadense.
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By going to form rather than species in this book regardless
what comes out of the future revisions this book will never go
taxonomically out of date. It also clarifies species concepts;
you can’t have a species without form. Every valid species is in
fact is a form in this genus.
So using form here in this book brings the ultimate clarity
available to each of the 16 forms that reside in this genus. We
hope this will inspire others to do research, but more
importantly new collection and sightings to make a better visual
profile of this genus.
Although the concept of peer-review is great it was never a
concern with the concepts of this book. Getting the facts right
was. We put all the information needed about this genus in one
place for the first time in 178 years, to the memory of Thomas
Say.
“Darwin’s species concept was not peer-reviewed”
Thomas Say started the interpunctatum adventure before dying in
1834. Someone one his behalf after his passing on erected true
interpunctatum in 1839 after his death and before the book The
Complete Writings of Thomas Say.
It is a nice feeling to finally have the genus all in one place
and as complete as possible.
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Stenacron Mayflies
Larvae
Illustrations by the author except
Page 103 figure 1, YIN-CHI-HSU
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Preface
The main objective of this guide is to provide a platform that
enables everybody to be able to use it. Whether you are young
child, or a biologist. You can utilize just the illustrations,
to make a reasonable identification. The illustrations presented
are from verified samples by the author, and they meet the
criteria of all past taxonomic studies, by way of descriptions
and moreover by intense rearing. Each illustration represents
each form in the genus as an average perspective, but are
typically made on one
particular sample. Although
like
everything in life, variation is an important thing to
understand as no two samples are truly the same. There are many
variations created by geological substrate composition. These
kinds of samples are not hybrids but rather form variations and
should be viewed as the nearest form.
Characteristics of the genus
All Stenacron larvae regardless of form or species are
Characteristics from all other Heptageniidae by their gills.
Gills 1-6 are pointed at the apex with a submarginal rib
and have fibril gills on the ventral side. Gill 7 is thread
like, with fine setae on the posterior edge. See anatomy
section for more details.
Gill 1-6
7th gill
By using this character you can establish that your sample is in
fact a Stenacron. In most samples they will also often have pale
stripes on the dorsal side of the abdomen as seen in the
illustration above.
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Valid species list for 2020
Stenacron candidum
Stenacron carolina
Stenacron floridense
Stenacron gildersleevei
Stenacron interpunctatum Say
Stenacron minnetonka
Stenacron pallidum
Stenacron interpunctatum / interpunctatum
Interpunctatum complex synonym forms;
Interpunctatum / affine ……………… (syn)
Interpunctatum / areion ……………… (syn)
Interpunctatum / canadense …………(syn)
Interpunctatum / conjunctum……….(syn)
Interpunctatum / frontale ……………(syn)
Interpunctatum / heterotarsale (syn)
Interpunctatum / majus ………………… (syn)
Interpunctatum / proximum…………… (syn)
Interpunctatum / ohioense…………… (syn)
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Life cycle
The life cycle or life history of Stenacron is basically the
same as most mayflies. Stenacron have a one year life span of
which most of it is spent as a larva under water.
They start as an egg then become the larva. The larva stage has
24 molting cycles where they shed their skin by growing larger.
Once the wing-pads reach the 2nd segment of the abdomen their
length has been established. When they reach the 24th instars or
last molting stage the wing-pads have reached the 4th segment
and they will hatch within one week, as seen in the larva
illustration above. At the end of the last instar they swim to
the surface of the water, split their skin and become the dun or
subimago. In 24hrs to the hour, they split the subimago skin and
become a spinner or imago the final stage. Next they mate in the
air, and then females drop the eggs into the stream and die. The
cycle then starts again with new eggs and larva.
Collecting larva
Collecting Stenacron larva is unlike any other genus. In the
case of Stenacron because of environmental preferences, using
the typical technic of a kick net or Seine will not provide good
results. We filmed a video on collection that we strongly
suggest you watch. You can access the video on YouTube under
this title;
Stenacron comadidum mayfly ecology documentary
Collecting larva requires you to lift larger rocks typically
larger than 6X6 inches with flat bottoms. You must slowly lift
the rock out of the water, flip it over and examine the under
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Stenacron 2020
surface for their presence. You will need to carefully remove
the larva from the underside of the rock. We have adopted
utilizing artist brushes to remove the larva from the rock. Be
very gentle with the larva so as not to remove their gills. You
must encourage the larva onto a fan blender brush. Then simply
place them in a bucket of water from the stream. See behavior
and ecology for a complete understanding of the environmental
preferences.
Rearing larva
Rearing Stenacron larva is quite simple. Collecting them is far
more difficult. You will need a small fish tank with a basic
oxygen pump. In the early spring in the end of March place rocks
and debris on the bottom from your local stream and fill ½ way
with stream water. It is very advisable to find one rock covered
in green algae. The typical green algae is long and stringy and
typically is the species Cladophora. Place the tank in heavy
sunlight with the tank oxygen pump running. By the end of the
month you will have algae growing on the glass sides. Once you
have a good environment for the larva move the tank to an area
that has sunlight for several hours each day. Try to keep the
water temperature between 16-22˚ Celsius. Don’t worry about
having moving water they prefer slow moving waters. The most
important thing is to make sure the pump is making bubbles in
the water. Now collect larva and place them in the tank with a
lid on it. When they hatch the adults will typically be on the
underside of the cover.
Geographical distribution
Stenacron can likely be found anywhere east of the rocky
mountain range and have been somewhat reported in many water
systems in the eastern half of the continent.
With the common misunderstandings in the genus we should always
consider it possible that most of the forms could be in your
local area. We have solid scientific reporting for the valid
species as to their specific ranges, but little for the
interpunctatum complex. The further north you travel the darker
they seem to be. The darker forms are very common in southern
Ontario, but pale forms are more common in the southern tier
like North Carolina to Florida.
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Historical Outline
It all started for this genus in (1839) when Thomas Say a selftaught naturalist found what is now known as true interpunctatum
Say. There are many synonym forms that are part of a complex
that is referred to as the interpunctatum complex, but there is
only one true interpunctatum Say.
As time moved on after Thomas Say founded the species
interpunctatum other forms for the genus were found. Dr. Walker
an English entomologist found a form he named canadense in
(1853).
The next form found was Dr. Banks (1910) for the species
frontale. It was not until (1933) when Dr. Jay R. Traver erected
the Stenonema genus that the interpunctatum group was elevated
to super famous in the world of fly fishing and became a
household name.
Stenonema as a genus had 3 groups in it and one of them was the
interpunctatum group. In (1974) Dr. Steven L. Jensen erected the
genus Stenacron for the interpunctatum group. So from there
forward the genus sat pretty much untouched.
There have been many studies done since (1974) but little to
sort out the taxonomic confusion of the genus as a whole. In
(1947)
Dr.
Herman
T.
Spieth
attempted
to
revise
the
interpunctatum group. Yet more damage was done to the genus by
his study.
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However he really was on the right track. He even established a
frontale complex, but then synonymized it into interpunctatum as
a subspecies group. The most damage to the genus comes from the
two forms that are most common to see and photograph canadense
and ohioense.
When Dr. Spieth synonymized ohioense with canadense he wrote a
new description including ohioense for canadense and this is
where the trouble really started, and just were this book takes
off.
In order to offer options to the past problems we had to pick a
point in time were the genus was in its most correct state and
best overall condition.
Being a proud owner of a first addition of the Biology of a
Mayfly 1935 that seemed to be the most logical place to start.
Dr. Travers work here is the best one could ask for regarding
this genus. All the forms were well understood and very well
described.
She erected many new species concepts in the book for the
interpunctatum group. The area missing was she only described
the adults and not the larva. Unfortunately the larvae are the
most misunderstood. She did however create a table of keys and
couplets for the larva.
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Transcending Maculation
In this section we will review and come to understand the
transcending maculation marks. All Stenacron regardless of form
or species have genetic markings that are in the imago or
spinner stage. These marks no matter how faint are present in
the other two stages. Let’s take a look at the larva head of
ohioense the dark type. All the blackish marks marked in red
arrows will transcend in to the adult stage.
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Below the larva head capsule is the head of the subimago or dun
stage of ohioense dark. We must always remember that the adult
stage is merely and very temporary reflection of the larva.
Now when we look at the larva illustrations we can see all the
body and facial markings that transcend from the larva stage
into the adult stage.
Notice all the arrows and numbers. They are there because in the
guide there is a table list of critical feature markings that
will help you best determine the form and or species. The tables
we have made are similar to the paint by numbers concept but we
are just following the numbered patterns.
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The comparative discussions will really help you understand the
differences. Here we look at and compare the two closest forms.
You will quickly see that although very similar and they do
share a lot in common, they can be separated by more features
than they share. Here are some illustrations that show two
samples that are very similar but yet very different, and in
this guide you will learn to separate all the forms.
The biggest and most important separating features are the black
spiracular spots on the sides of the abdomen and the physical
size. If you can see the difference between them you have just
done what was very difficult to do prior to this guide. Even
some of the finest biologists of the day have trouble separating
them until now. The two used for the sample are the two hardest
to separate in the entire genus being ohioense and canadense.
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Here is a larva sample of two forms that are very hard to
separate. The forms are canadense and interpunctatum (Say) the
real interpunctatum not one of the synonym forms.
One important note is the canadense illustration was based on a
female sample not a male as in the interpunctatum. This is the
reason it is orangey in color. It is not hard to see why these
two are so difficult to separate. Now let’s look at them from
just the abdomen perspective. They are in the same order
canadense first interpunctatum Say second.
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Stenacron 2020
The principle difference is the sublateral streaks. These are
the pale stripes that are closer to the lateral edge. The other
interesting note is the brownish coloring. In the interpunctatum
that coloring is very pale cinnamon colors rather that darker
brown as in the canadense.
The physical size is the most important feature. Canadense is
much larger than interpunctatum Say. This now gives you an
understanding of the guide and how it works.
By putting samples side by side it makes it very easy to see the
differences. The very detailed individual descriptions and the
tables of features will further aid you through your research.
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Male from Female
It is quite easy to tell a male larva from the female larva.
Here are three things that allow separation. First the male will
have claspers at the end of the 10th segment on the ventral
side. Second is the size and spacing of the compound eyes. The
first photo is a male the second is a female.
Notice how large the male eyes are and tightly they are placed
together. An interesting and unknown fact is the markings on the
underside of the abdomen.
The lateral markings on the female typically start on the 1st or
2nd segment to the 9th. On the male they are generally from the
6th–9th. In some of the valid species like candidum the markings
are the same from the 6th-9th in the male and female. Also if the
females are relatively mature they will be orangey in color in
the abdomen as they carry the mature orange eggs.
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Hatching Periods
These dates are based on historical records and are put together
here to help hypothesis local hatching performance. All the ones
marked with a star are the original collection dates.
There has always been talk about the darker forms hatching in
spring and the lighter smaller forms hatching in summer through
fall.
We are not sure that this thinking is correct for this genus.
Some of the original darker forms were collected in the latter
part of the season. An example is gildersleevei. According to
Traver they hatched in late August through September, and we
have collected the larva at that time frame in only the 21th
instar. That means that the larva collected was not set to hatch
till October.
Moreover we have collected and reared ohioense from the middle
of June through to middle October.
From my rearing and study we propose that based on historical
data and current studies that most Stenacron like hatch all
season long. And they likely have bursts of hatching throughout
the entire season.
affine (Traver 1933);
*Traver April 29th - June 10th 1929 Sophia NC Halotypes
areion (Burks 1953);
*June 25th 1948 Oakwood Illinois Halotypes
canadense (Walker 1853);
Clemens reports Ontario 1913; June 25th - July 15th
May 22nd Lowville park 2014
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candidum
Stenacron 2020
(Traver 1935);
*Traver June 18th 1929 Black mountain NC Halotypes
carolina (Banks 1914);
*Banks says Black mountain NC, (May) Halotypes
conjunctum Traver 1935;
*August 24 1932 through mid-September NY. Halotypes
August 28th 2014 Progreston dam
floridense
(Lewis 1974);
*No collection dates known Gadsden county Florida Halotypes,
hatches throughout the year
frontale (Bank 1910);
*Banks Gloversville NY May 15 1910 Halotypes
Clemens reports Ontario June 15th - July 10th 1913
gildersleevei (Traver 1935);
*Kirkland Ohio 1930 Halotypes August 31st to early September 3rd
heterotarsale (McD 1933);
*July 2nd 1924 Halotypes / Paratypes
June 27th - August 9th Ottawa Ontario
interpunctatum (Say) 1839;
*Say 1839 Washington Indiana no dates Halotypes
Hagan 1861 Trenton falls Chicago Illinois
Hagan 1861 Allegany mountains Virginia
Beacon Lowville park July 1 first 2014
34
Stenacron 2020
majus (Traver 1935);
*Traver July 16th 1932 Ithaca NY Halotypes
minnetonka (Daggy 1945);
*June 14th 1930 Mound Minnesota Halotypes
pallidum (Traver 1933);
*Traver May 12th 1929 - May 18th 1930 piedmont NC Halotypes
proximum (Traver 1935);
*June 10th - June 20th White church Ithaca NY Halotypes
May 30th Progreston dam
ohioense light (Traver 1935);
*August 7th - Aug 18th Painesville Ohio Halotypes
June 13th Lowville park 2014
Ohioense dark (Beacon 2014);
August 26 2014-October 20th 2014 Progreston dam Bronte creek,
southern Ontario.
35
Stenacron 2020
Sorting Larvae on site or in the lab
Get a main sorting container with a full mix of larvae samples.
Every sample that has a wingpad less than the posterior edge of
the 2nd tergite can be put back, diagnosis is too difficult.
Once Stenacron larvae wingpad’s reach the posterior or the back
of the 2nd segment the larva is full grown in length. When it
reaches the back of the 4th segment the larva will hatch anytime
within a week.
Complete stripes
incomplete stripes
The greener the wingpad are the sooner they will hatch. Next
divide them in two major groups. Ones with complete pale stripes
on the top of the abdomen, and ones with incomplete stripes in
36
Stenacron 2020
the other container. Once you have sorted them by stripes the
next is to sort them by lateral projections of the 8th and the
9th as per lengths regarding equal or shorter, and still include
stripes. You now need to use 4 containers. Be sure to only sort
samples from the same substrate. If you change the geological
fundamentals of the substrate being dark or light you will find
variations of form making sorting extremely difficult.
A
Container
A;
Container
B;
Container
C;
Container
D;
B
C
D
for complete stripes with equal lateral
projection.
complete stripes shorter 8th lateral
projection.
incomplete stripes with equal lateral
projection
incomplete stripes with shorter 8th
lateral projections
If you have a sample that has a longer 8th projection and has
discontinuous stripes it is Stenacron carolina as it is the only
one in the genus with a longer 8th than 9th and this is what
carolina looks like.
Now you can further dived the group until everyone in each group
looks the same. Once this is done you can use the head
capsule/pronotum maculation markings and the pale spots in front
of the median ocelli or simple eye and very important the size.
Here is an up to date copy we made of Travers original larva
table 1935. We were able to add 5 forms. All up dates are
37
Stenacron 2020
highlighted. Larva must be measured while alive, abdomens expand
at death.
Species or form
1 ♂-♀
2
3
4
5
6
(8th is)
Affine
Areion / unknown
7-9
7-9
N
--
Y
--
Y
-
N
-
equal
unknown
canadense
candidum
carolina
conjunctum
frontale
floridense
Gildersleevei
heterotarsale
Interpunctatum *
10-13
8.5-10
10-11
8-10
8-10
8-10
11-13
9-11
7-9.5
N
N
N
N
Y
Y
N
N
N
Y
N
N
Y-N
Y
N
N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
N
N
N
N
N
N
Y
N
N
equal
shorter
longer
equal
equal
unknown
equal
equal
equal
10-12
8-10
10-13
6- 7.5
9-11
Y
Y
N
N
Y
Y-N
Y
N
Y
Y
N
Y-N
Y
N
Y
Y
Y
Y-N
Y
N
1; Body length is expressed in millimeters (♂ is the smaller
majus
minnetonka
ohioense
pallidum
proximum
2;
3;
4;
5;
6;
equal
unknown
sub-equal
Shorter
shorter
number)
Median pale spot on the frontal shelf of head capsule.
Continuous pale submedial streaks on abdomen.
Ventral markings on the lateral areas of the abdomen.
Posterior edge of tergites dark or blackened.
Later projection of the 8th VS 9th for spine size.
Note; regarding column 3; there is new evidence of geological variations. When they
affect the table they are noted as Yes and No mean that they have both continuous and
discontinuous stripes.
Note; there are no records for lateral projections for any new species after Travers 1935
table. So Minnetonka and floridense are unknown, and areion was never collected as a
larva stage.
For a clear understanding of light and dark types of the same
form you must read the leopard larva changed its spots. The dark
type only comes from a black-dark brown substrate.
The light type only comes from medium to light colored
substrates. Knowing this aids you in sorting to the most logical
form and or species.
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Stenacron 2020
Container A; continuous stripes, equal projections
• canadense
• interpunctatum Say
• conjunctum light type Light substrate only
• frontale
• majus light type
Light substrate only
• heterotarsale
• affine
Container B; continuous stripes, shorter 8th projections
• ohioense light type Light substrate only
• proximum light type Light substrate only
• pallidum
Remember ohioense has sub-equal projections
Container C; discontinuous stripes, equal projections
• gildersleevei
• conjunctum dark type Dark substrate only
Container D; discontinuous stripes, shorter 8th projections
• candidum
• ohioense dark type
Dark substrate only
• proximum dark type
Dark substrate only
Remember ohioense has sub-equal projections
We can clearly see that container A is the most difficult to
sort out. Here are samples of head capsules and median ocelli
markings. All 5 below are in group A, so use the head capsules,
and median ocelli marks to help you.
39
Stenacron 2020
If further diagnosis is needed remove the labrum and compare to
samples that we blueprinted in this book. Everything in group A
was blueprinted except affine.
Behavior and Ecology
Stenacron larvae have very specific ecological requirements that
are found in all moving watersheds in North America. However
they seem to prefer lower altitudes and meandering waterways.
Stenacron can likely be found anywhere east of the rocky
mountain range, and have been somewhat reported in many water
systems in the eastern half of the continent.
The basic substrate requirements are. Slower moving currents
generally under (10) MPH, with light sedimentary levels. Light
plant growth is important, with larger loose rocks that are not
cemented in by sedimentation.
The sizes of the rocks are critical to Stenacron. They must be
larger than 6x6 inches and about 2 inches thick with flat
bottoms that are clean of sedimentation and slime.
Stenacron tend to hide on the underside during the daytime and
actively feed on the topside of the rocks during the night.
There also seems to be some levels of social society during none
hatch times. They spend a great deal of time in non-foraging
situations in a community based environment. However in the
evening when feeding it’s every larva for himself and there does
seem to be a pecking order with food resources.
In most situations the larger male larva will chase of others,
even females from a debris pile. The females are nonaggressive
and tend to not participate in the pecking orders but rather
move from one area to another when foraging.
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Stenacron 2020
Stenacron interpunctatum larvae according to McCshaffrey &
McCafferty (1986) are not scrapers but rather collectors and
gatherers and are considered opportunistic feeders. Gut contents
of studied larva showed a wide range of organic matters.
Their study clearly indicated that mineral material and organic
detritus are the most important, and that diatoms from scrapping
were only found in few samples.
In our rearing experiments with the genus and the form ohioense
in an enclosed tank, the algae growth on the glass is clearly
desired by the larva. In the middle of the night after 1:00 am
and before 4:30 am they are on the glass sides feeding on what
appears to be the algae growth of Cladophora.
Although very sensitive to light, after a few days in the tank
they seem to not run for cover by the usage of a flashlight when
on the glass sides. However if they are on the topsides of the
flat rocks, or collecting on the bottom in the debris, they
quickly move to the underside of anything to avoid the light.
In the form ohioense their eyes are very reflective to light in
the larva stage suggesting they have excellent night vision.
Another interesting thing about Stenacron is the lighter forms
like heterotarsale and interpunctatum Say are less sensitive to
light and the larva’s compound eyes are less reflective. These
forms also operate in the day light as far as hatching and
feeding goes.
The preferred time frame for molting of the form ohioense larva
between instars seems to take place early in the morning around
5:00 AM. This does seem to align with the amount of time
required for the maculation process to be completed. In our
observations it takes around 8hrs, in the tank to completely
return to their dark coloration. The tanks water temperature is
typically 2-6 degrees warmer than the river system.
So that suggests it is very reasonable to assume that in colder
water the time frame would likely take a little longer more like
12 hrs. This lines up nicely with the time to come out and
forage on the topside of rocks. Other experiments with ohioense
in captivity with oxygen depletion per environment.
41
Stenacron 2020
This involved the testing of survival in lowered dissolved
oxygen or (DO). Stenacron ohioense and many other forms in the
genus show the ability to survive with little oxygen in water
that is not moving.
Experiments were carried
out in several
different size
containers ranging from a small bucket to a petri dish.
Interesting is their ability to adapt by slowing the rate of
their gill pulsing to seemingly suit their environments.
Stenacron larva can bring their breathing rate down to the point
that little gill movement is seen. Yet one might first think
that they may be expiring, but a genital touch with a brush, and
they start to breath normal.
Before we go too far let’s take a minute to discuss another
relative topic. In our observational studies, Stenacron have the
ability in the larva stage to suffer high anxiety. Stenacron
show a panic attack type state when in tight confinement. After
an initial adjustment to a new environment they tend to relax
remain somewhat motionless and eventually adjust their breathing
rate to fit their current environment.
Stenacron can survive in low dissolved oxygen (DO) for extended
periods of time. One of our experiments involved placement in a
petri dish in 10ml of oxygenated water for up to 6 hours and
they showed no discomfort or desire to be removed. Other
experiments are the rearing to adulthood in 5ml of water.
Stenacron seem to be very adaptable with a strong sense of their
environmental requirements and surroundings.
When faced with a choice they seem to show a great affinity to
choose what they best need. Taking the dark type of the form
ohioense for this experiment, when faced with a choice to pick a
dark rock or a light rock to cling to, this dark form always
picks the darker rock. They may at times first pick the light
rock but will change rocks to the darker one. What this suggests
is they are aware of their pigmentational value and their
environmental needs. This does not suggest any specific level of
intelligence but rather a strong intuitive natural instinct for
survival.
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Stenacron 2020
The hatching behavior of the form ohioense is also unlike most
Stenacron, and other Ephemeroptera. This form only hatch’s to
the adult stage between the hours of 11:30 PM and 4:30 AM.
Adapting to this hatching strategy is quite interesting to say
the least. It certainly shows great adaptability for survival as
a whole. The predators of all mayflies are birds, spiders, and
dragonflies and of course fish. Hatching in the night time
removes two of the main predators because birds and dragonflies
rest in the evenings.
Most Ephemeroptera hatch in the lowering light at the end of the
day in the summer and into the early fall. In the spring many
genus hatch from midafternoon till dusk when the water
temperature is warmest.
Stenacron ohioense seem to prefer the cooler temperature for
hatching. Although it may have more to do with them being a form
that utilizes the darkness for all aspects of their existence.
In the headwaters of streams and dealing with the darker forms
like ohioense, canadense, and gildersleevei that hatch in
smaller numbers it is interesting that they pick the night to
hatch and feed. By removing the two main predators from the
equation the survival rate would very likely go up.
Headwaters have smaller areas that hold Stenacron populations
being mostly at the sides of the system and tails of pools.
Which in turn suggest that the headwater populations are in fact
smaller than in the larger systems? Historically Stenacron or at
least some of the forms are known for being able to live and
even flourish in populations in compromised water conditions.
With so little known about the larva in the past and present,
this is very hard to confirm.
Lewis (1974) commented on heterotarsale as being the only
Stenacron form to live in waters on the Ohio River just below a
sewage treatment plant. This very much suggests a higher
tolerance
to
toxic
waters.
Yet
more
than
90% of
all
heterotarsale larvae in our collection came from cleaner or less
compromised waters.
43
Stenacron 2020
The form ohioense both light and dark types are collected from
headwaters and midstream areas. What is really striking is that
the greatest numbers of ohioense are in very close proximity to
6 different forms of Epeorus in high (DO). Epeorus have set
standards for water qualities, and show the water must be very
clean with a high DO, and spring feed is preferred.
With that said it leads us to only presume that ohioense is a
clean water dweller. Yet we can collect a few here and there in
waters that would normally be considered compromised. Here in
the
great
lakes
area
some
waterways
historically
were
compromised by agricultural pesticides and industry.
In this time frame most of the agricultural is gone, and
industrial regulations have increased which has helped improve
the water conditions, or so we can believe. With the highest
populations of ohioense within 60 yards of Epeorus, and having
the ability to survive in a low DO. We can only conclude that
the water must be clean in this area of Bronte creek. This in
turn says a lot about the entire genus needing clean waters over
higher dissolved oxygen’s. Cohabitation of other forms of
Stenacron with ohioense is very high. For example all of the
following forms can be found within 5 miles of ohioense and more
typically within 2 miles.
Canadense, frontale, majus, proximum, candidum, interpunctatum
Say, conjunctum, & gildersleevei.
This in turn completely suggests most Stenacron should be
considered clean water dwellers. This however does not change
the fact that interpunctatum Say and heterotarsale are commonly
collected in somewhat compromised waters.
The form candidum seems to also be collectable from the same
location as heterotarsale in Selkirk Ontario.
The following table was created to directly reflect Lewis 1974
for the EBI biotic list. The scale is 1-10; 0 being intolerent
to any toxic or organic pollutions, and 10 being toxic
satutation or uninhabitable. The forms at the bottom and marked
with a star are collected by me and the rating given was based
on ohioense being a clean water dweller. Lewis posted frontale
as ID insuficiant data. Our collections show it in proximity to
ohioense but with proximum and majus. Untill futher data can be
created these numbers should be considered resonable.
44
Stenacron 2020
It is our hope that further studies of the genus will create
even more accurate numbers that provide a greater understanding
of the entire genus.
Form
Candidum
0
Canadense
Carolina
0
Floridense
0
Frontale
Gildersleevei
0
Heterotarsale
Interpunctatum s.s
Minnetonka
Pallidum
Conjunctum *
Majus *
Ohioense *
0
Proximum *
Interpunctatum Say *
1 --------------------------------------------
10 ID
1
2
X
7
4
6
1
1
2
2
2---------4
All of the herterotarsale collected by us are in a waterway
known to us as Selkirk creek in Selkirk Ontario which is
effected by moderate local agriculture and the water quality is
unknown to us. Based on the historical levels provided by Lewis,
and the poor conditions of the creek, we can only conclued it is
effected by the local agriculture. This brings us to the
discussion regarding candidum. The table created by Lewis states
that candidum has a rating of 0, but our primary collections of
this form show it in Selkirk creek alongside heterotarsale. It
is also collected in Bronte creek in good numbers along-side
conjunctum, majus, proximum, and ohioense. So the question now
is. Should Stenacron as a rule be considered intolerent to
compromised waters? Or are they just that adaptible that they
can live in all conditions and would just prefer cleaner water?
Based solely on collection population numbers collected per
area, Stenacron seem to show a direct preference to cleaner
waters. Creating laboratory studies with controlled toxic
conditions is likely the only way to truly determine the
tolerance levels for each form. However unlike any past studies
larvae scrutiny must be very high and all samples must be
identifide to their legitamate forms prior to study, and must be
stated as such.
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Stenacron 2020
The Leopard Larva Changed It Spots
New larva morphological information has been found! Before we
review these findings let me quote a few important statements
from previous authors on this genus to set the pace.
Spieth 1947; “No experimental evidence exist to indicate how
much or how little coloration of the imaginal individuals of
this genus is independent of the environment in which the nymphs
develop. Circumstantial evidence Spieth (1938) indicates, and
such evidence is constantly accumulating, that the environment
may play a part in determining the degree of coloration of the
adults”.
Spieth 1947; “When confronted with a large series, especially
from the areas around the Great Lakes, more “intermediate” than
“typical” specimens are invariably found”.
Lewis 1974; “Studies should be designed to ascertain whether the
apparent hybrids are truly hybrids or are environmental variants
within species. The influence of glaciation and biogeography on
the distribution of several populations needs investigation”.
This genus is without question a special one as to have created
such a mystery surrounding them. So much effort was spent on the
hybrid theory that the truth was never found until 2014. A
recent discovery through isolation rearing has shown all the
true variations.
This genus has very special qualities to it that no other to my
knowledge has. There are multiple forms of larvae for one adult
form. The variations are caused from the geological substrate
composition and not geography as previously thought to be.
46
Stenacron 2020
On August 26th 2014, larvae were found that did not match any
larva known in the genus. The adults seemed to align somewhat
with Travers 1935 ohioense. Without males we could not conclude
with assurance that it was that form. After reviewing 4 males
the conclusion was, it is in fact a geological variation of the
form ohioense.
Interestingly enough there are at least 2 distinct larvae forms
that reared out to ohioense. Referring to them as the light
type, which meets the criteria of the historical profile created
by Traver (1935), for this form in the larva state. The other is
the dark type, which is only found on very dark background
substrates.
The principle difference in the adults is the lack of median
line, and the sublateral shading on the dorsal side of all
tergites. The principle difference in the larvae is the
discontinuous submedial abdominal stripes in the dark type and
continuous stripes in the light type.
47
Stenacron 2020
In the adults the light type has a deletion in maculation of the
median stripe making them look like a hybrid of ohioense & majus
or a true frontale. The dark type rears out with a complete
median line.
With this new information a review of all the larva forms began,
to see if others possibly have this very distinct morphological
trait and conjunctum and others, also have this substrate
camouflaging trait.
Both ohioense and conjunctum type larvae were collected on
Bronte creek and the two collection sites are 3.9 miles apart.
The stream has a very dark bottom with blackish sediments, and
is turbulent, as you go upstream to Progreston dam. And, becomes
meandering with higher levels of pale clay sedimentation as you
go down stream to Lowville Park.
Substrates of the Niagara Escarpment;
1: Very dark black rocks and dark soil sedimentation
represent the Progreston dam site for the dark forms.
to
2: Moderate coloring, having lime stone rocks with red clay
sedimentation with appropriate Cladophora algae levels to
represent Lowville Park for the intermediate forms.
3: Very pale background consisting of white and red clay
sedimentation, to represent collection sites at the mouth of the
watersheds for the lightest forms like interpunctatum Say and
heterotarsale.
In the following picture we can clearly see the difference in
the two substrates of the upper areas of Bronte creek in
Southern Ontario. On the left are rocks removed from the upper
areas of the creek. To the right are rocks from the site at
Lowville Park.
48
Stenacron 2020
The geographical fundamentals of the Great Lake region are. All
streams or rivers that flow from the Niagara Escarpment to the
Great Lakes all possess these three basic substrate types. In
their uppermost headwaters they are spring feed with dark
substrates.
As they fall over the Escarpment they enter the red clay plane
region and become meandering in nature. Red clay bluffs become
the rule, and during rains flood with red clay silt runoff. When
we enter the lower basins they are completely saturated in both
white and red clay sedimentation to the point that little
aquatic life exist.
However with regards to Stenacron having a diet that mostly
consist of mineral content it is not uncommon to find the forms
heterotarsale and interpunctatum Say, where little or nothing
else exists.
By replicating their environments we can anticipate that each
form should have at least 3 variable larvae and adult types that
rear out with the mid-range adults matching the historical
profiles. This intense type of rearing program can help create
new revealing data.
49
Stenacron 2020
It will allow for boundaries in understanding the variability to
be set, in what is an acceptable variation from the true
historical profile. We can surmise the following based on the
new current larva evidence.
ohioense; very dark form with 3 types that represent the total
forms historical profile. The lighter of the type looking very
much like a dark frontale and the darkest similar to
gildersleevei.
frontale; a moderate form that could have 3 types that represent
the total form with the lightest variation being very much like
proximum, and the darkest more towards ohioense.
proximum; one of the lighter forms in the complex that should
also have 3 distinct types, the lightest looking like conjunctum
or majus, the darker nearing frontale.
conjunctum; one of the lightest forms in the complex, with
likely 3 different types, the lightest like majus and the
darkest similar to proximum.
majus; being the lightest overall in the complex and having
likely 2 distinct types, with the lightest missing pleura
streaks, spiracular spots, and the median dorsal line, and
looking like interpunctatum in appearance, the darker form
similar to conjunctum.
Clearly with this new information and a well-planned rearing
platform we can expect there are no hybrids, but we can
anticipate and document all the variable types within each form,
and create expected variation boundaries. At this point we see
no evidence for the hybrid theory. We find more evidence against
it, but no one can truly rule out nature at this point.
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Stenacron 2020
Range and Distribution
Serious taxonomic confusion exist in this genus, so finding and
establishing true range boundaries is nearly impossible.
Therefore it is my opinion based on spending the last 8 years
looking at every photo on the internet and its location.
Stenacron seem to be everywhere the altitude is moderate to low,
with an average altitude of about 700 feet.
To try to get a better handle on this we are offering here an
altitude table above sea level from the very first locations
where species was established. We have seen here on Bronte Creek
in Southern Ontario that forms and species distribution in this
one watershed is specific to their special ecological and
dietary needs. We suspect in all situations there are large
areas of overlap and we have seen high cohabitation of forms
inside 3.9 miles range. Altitude is feet above sea level based
on original site. Walker 1853 only states Canada, for canadense.
Form / species
affine
areion
canadense
candidum
carolina
conjunctum
floridense
frontale
gildersleevei
heterotarsale
interpunctatum
majus
minnetonka
pallidum
proximum
ohioense
Holotypes location
founder
Sophia NC
Oakwood IL
No true location
Eddyville IL
Black mountain NC
Pleasant valley NY
Gadsden county FL
Gloversville NY
Kirkland Ohio
Ottawa ON
Washington IN
Ithaca NY
Mound MN
Piedmont NC
Ithaca NY
Painesville Ohio
Traver
Burks
Walker
Traver
Banks
Traver
Lewis
Banks
Traver
McD
SAY
Traver
Daggy
Traver
Traver
Traver
year
1933
1953
1853
1935
1914
1935
1974
1910
1935
1933
1839
1935
1945
1933
1935
1935
altitude
1315
591
0
680
2199
192
134
750
1163
210
495
369
2301
1100
369
618
This
table
suggests
that
affine,
candidum,
carolina,
gildersleevei, minnetonka, and pallidum all prefer headwaters of
the systems at higher altitudes where the water is spring feed
with a higher dissolved oxygen (DO).
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Stenacron 2020
Now we will use the same chart for forms and species taken from
Bronte creek in Sothern Ontario. The higher the elevation the
cleaner the water and the faster it is moving with higher
dissolved oxygen levels (DO). Bronte in the very headwaters is
totally derived from springs. The upper areas have less
appropriate environments for the genus being the sides of the
system meaning smaller populations.
Form / species
canadense
candidum
conjunctum
frontale
gildersleevei
heterotarsale
interpunctatum
majus
proximum
ohioense
location
Lowville ON
Selkirk ON
Progestin Dam
Lowville ON
Lowville ON
Selkirk ON
Lowville ON
Lowville ON
Lowville ON
Progestin Dam
founder
year
Walker
Traver
Traver
Banks
Traver
McD
SAY
Traver
Traver
Traver
1853
1935
1935
1910
1935
1933
1839
1935
1935
1935
altitude range
350
540
350
350
350
540
350
350
350
350
-
400
720
720
270
270
500
400
720
The high percentage of collected samples was at about 400 feet
above sea level. Ide 1935 commented that on the Mad River here
in Ontario at 750 feet that frontale, canadense, preferred the
upper areas, and heterotarsale preferred the mid 300 feet range
but they did overlap making streamside identification difficult.
The reason for disusing range and altitude is we believe that
most forms likely utilize a lot of the eastern seaboard.
With the darker forms mostly occupying the northern range and
higher altitudes, and the lighter forms occupying the middle to
lower range and lower altitudes. It has been the common thinking
for decades that the dark forms are more northern and lighter
forms are more southern.
There is no question until this guide taxonomic confusion was
very high regarding the larva everything with stripes was
basically interpunctatum, when nothing could be further from the
truth.
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Stenacron 2020
With misunderstandings in laboratories and in the field getting
a true range in this genus is near impossible. You should likely
expect to see a high percentage of these forms all over the east
coast range. Darker forms or species tend to prefer darker
substrates and the lighter forms and species a moderate color
density substrate. Reading the section the (Leopard larva
changed its spots) we go more in detail about this. You will
likely find a form or species in one area of the system, with a
moderately dark substrate, and 2 miles upstream find the same
form or species and it would look totally different in color
maculation if the upper area has a darker substrate.
The original range established by Lewis 1974 floridense is in
the upper west areas of Florida near Mobile Alabama. We are
showing here some samples that are outside the reported range
that could be Stenacron floridense.
The larva of floridense has a very specific maculation pattern
on the dorsal side of the abdomen. We did our illustrations for
this species based on Lewis description 1974 and 3 samples in
the Bold System Museum website. We also have a sample of
frontale from the same location and same source showing the very
pale maculation in the photo plate section.
The characteristic submedial stripes on all Stenacron get bigger
as the substrate lightens and the same in reverse. We know and
trust the source as a very reliable and accurate collector. This
sample larva was taken from the shoreline of Norris Lake
Tennessee. Sharon has confirmed that the substrate is very pale
mineral based going to the pale color. The adult female is also
from the same location.
Without dissection of the larva there is no 100% assurance but
with the tergite pattern confirmation from a photo is very high
from our perspective. The female imago has a special marking
that no other in the genus has, being a moderately sized red
spot on the vertex of the adults with black ringed ocelli. This
is not a brownish-red, but rather true reddish spot as stated by
Lewis 1974. We are using this sample as a reason to always
consider range as “suspect” for Stenacron. Here are the samples
of the larva first including samples from Bold Systems.
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Bold Systems 2 samples photos Jeff Webb; floridense
Notice the submedial spots on the 3rd segment are slightly enlarged
Our illustrations;
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Now this is the sample taken by Sharon Moorman; La Follette
Norris Lake, Campbell County, Tennessee, July 29, 2014.
We think it’s clear from this exercise with the larva and this
headshot of a female imago that are suggestive that floridense
range might go nearly to the boarder of Kentucky in the lower
elevations. The red spot and black ringed lateral ocelli are
very noticeable as per Lewis. Whether it is floridense is not as
important as the reasons to be “suspect” about Stenacron ranges.
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Of course without laboratory results this is only a reasonable
conclusion. We hope that this will encourage science to more
intense reviews and collect more Stenacron to try to give some
basic geographical and geological boundaries to the forms and
species that reside in this genus.
The sample from Fort McCoy FL also has a pale brown-red like
spot and is only 90.2 miles from the set boundaries by Lewis
1974. For the Bug Guide site we have marked it as floridense.
After a second review Roger and I relisted it as interpunctatum
Say Lewis Berner 1986 has Stenacron interpunctatum Say as far
south as the Fort Meyers Florida range so having floridense that
far south would also not be a surprise.
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Biodiversity
Here we will breakdown Bronte Ck collections for all of the
forms in that creek, and map out all the forms in the genus from
it. We have not collected heterotarsale in Bronte. In the chartgraph below you can see the elevation drop. At location (A) it
is Progreston Dam at 720 feet above sea level. Location (E) is
Lowville Pk at 350 ft. At collection site (F) few Stenacron were
found. Collection site (G) only 6 was found all being
interpunctatum Say, and canadense.
Primary collections took place at (A-B-C-D-E) in total nearly
400 sample per year were collected from the combined locations
on just Bronte. It is important to remember the substrate
variation. At site (A) it is very dark and at site (E) it is
intermediate in color density. Site (A) has very little
sedimentation and it is dark chocolate brown black. At site (E)
it is principally limestone rocks and red-clay-shale shaped and
rounded into flat reddish rocks, with heavy clay sedimentation.
Site A
Site E
Between site (A) and (E) there is an altitude drop of 370 feet
for the 3.9 mile span. The water is cleaner, faster, and darker
at site (A). It is slower, not as pure and paler causing
pigmentation shifts in the larva. We will now group collections
from (A-B-C-D-E) and show you the forms collected but also
whether they were the dark types, or light types, and a basic
collection population breakdown per area.
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Site (A);
•
•
•
•
•
Progreston dam Carlisle On
ohioense dark
60%
conjunctum dark
20%
proximum dark
10%
frontale dark
8%
candidum
2%
•
•
•
•
•
1000-3000- yard down
ohioense dark
conjunctum dark
proximum dark
majus dark
candidum
stream
40%
30%
20%
8%
2%
•
•
•
•
•
½ mile west of Cedar
ohioense dark
conjunctum dark
proximum dark
majus dark
candidum
Springs rd.
40%
30%
20%
8%
2%
Site (B);
Site (C);
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Site (D);
•
•
•
•
•
•
intermediate maculation
ohioense
30%
conjunctum
30%
proximum
20%
majus
15%
frontale
10%
canadense
5%
•
•
•
•
•
•
Lowville park, Lowville On
ohioense light
30%
conjunctum light
25%
proximum light
15%
majus light
10%
canadense
10%
interpunctatum Say 10%
Site (E);
Now we will look at two males for ohioense, dark from site (A)
left, and a sample from site (E) right which is clearly the
light type. Even the yellow sheath covering the wings is paler
from the pale substrate. The one on the left from the dark
substrate clearly has a yellow abdomen, and yellow forewings.
Both samples are in the subimago stage and were reared in
isolation.
A
E
Not only are there differences in the general appearance there
are differences in population per area. At site (A) 60% of the
population was ohioense dark. By the time you get to site (E)
ohioense light population was down to 30%. You will also notice
that between site (D) and site (C) the forms were all moderate
in maculation density to light types.
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Cutaways of site location (A)
Cutaway of site location (E)
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All of the above information gave us and hypothesis what if all
Stenacron can be tracked by the elevations found in Bronte
creek. We could have never dream of the level of accuracy that
was involved. What we did was print out the following map and
look at every photo ever taken of any Stenacron.
What we did was identify the photo to form with at least 95%
assurance. Marked it on a non-elevation map as seen below. Then
transported the markings to a special elevation map.
Once all the red X’s where in place based on’ sightings and
elevation we found that our collection elevation sites having
certain forms in each area we found a geological and
geographical home for each species and form.
The map below is for 3 forms that all reside in Bronte Ck at a
certain elevation range being 350-720 ft above sea level. We
expanded the elevation to be likely as high as 800 ft. Map 1 was
transferred to map 2 the mountain range map.
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The yellow line is the outside of the elevation boundary, so
forms and species are found inside that area. Stenacron do tend
to use low level corridors for range extension. This is how they
can be on two sides of a mountain range they crossover in the
elevation that suits their needs. Also crossing over at the
headwaters at the top of a mountain. At the watersheds
beginnings they are the same on both side of the mountain.
Before we present the final maps for every form and species
there are two things to mention. First we did not mark out
areion as no range would be known all the samples came from the
same basic areas. Second is very important to know. The
Appalachian mountain range is the eastern continental division
for Stenacron. There has never been a sighting publically known
of a Stenacron in the Rocky mountain Range they have always be
viewed and seen as an eastern genus and this is correct.
Elevation from sea level is the cause there is more appropriate
environments and ecologies in lower altitudes as the water moves
slower which is the primary need for this genus, slower rivers
make billions of homes. This first map was perfect for the job
of building an elevation scale from to put inside each map so we
could find the basic elevations. The colors are not as accurate
as they could have been but it is enough to show this theory
works.
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The absolute maximum elevation we found was a female canadense
on Bold Systems from Alberta. Bold Systems inventory number is
ABMAY015-09
Stenacron
interpunctatum
[COI-5P:658]
the
elevation is 3840 ft making that the second highest elevation
for the genus ever recorded, other than carolina at up to 5200
feet.
The furthest west is also at Bold Systems being from the Yukon
Territory, Kluane National Park Canada, and the elevation is
2100 ft and here is the inventory number BBGCO934-15 - Stenacron
interpunctatum [COI-5P:534]. Because there is no photo, we could
not identify the form but it is most likely a true canadense.
The furthest east is a female canadense from Bold Systems as
well-being, New Brunswick, Miramichi Canada, at the Atlantic
inlet and its inventory number is, EPHNB005-09 - Stenacron
interpunctatum [COI-5P:658].
So we can determine that coast to coast Stenacron can exist but
only at certain elevations. We suspect that they will never be
found in the Rocky mountain range especially in the USA the
elevation is too high. The next map is a genus only distribution
map showing the general locations of the entire genus.
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There is at this point no reason to believe that with this very
far west sighting we may still find a few samples in between the
mountains from Alberta to the Yukon site but certainly not at
high altitudes. With the forms conjunctum, proximum, and
frontale all showing high cohabitation in elevation range, and
being responsibly difficult to separate we placed them all on
one map.
conjunctum, proximum, and frontale;
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The most northern sighted sample that could be identified to
form is a female that aligns with Traver 1935 for proximum on
BBEPT142-10
Stenacron
Bold
Systems
inventory
number,
interpunctatum [COI-5P:658]. The furthest south is Fort McCoy,
Marion County, Florida, USA on the bug guide. It is a female
sample that aligns within reason with floridense and is only
90.2 miles south east of the collection range set by Lewis 1974.
Identification in the subimago state is sketchy but we can see
in the head shot a faint but distinct pale brownish-red spot on
the vertex of the head. True interpunctatum Say does not have
that feature and is the only other form in that area. The
furthest south on record as we know it is in the Fort Meyers
Florida in Lee County from the out flow of Lake Okeechobee,
Berner and Pescador 1986 The Mayflies of Florida.
The first maps to review now is affine and heterotarsale. At the
behest of Dr Needham, Dr Traver synonymized affine to
heterotarsale and we believe for reasonable conclusions. In her
writings and on page 303 of The Biology of a Mayfly it is clear
she did not totally agree with the synonym. On page 303 below
the larva table she indicates “5, assuming that affine equal’s
heterotarsale”. Affine in the bottle here in the book shows
affine as having a dark brown mesonotum more like interpunctatum
Say. However our illustration was based on her descriptions and
has a lighter mesonotum. We are not sure and think the synonym
was questionable. Heterotarsale is much larger and has a
yellowish mesonotum. Interpunctatum Say is also closer in size.
Now reflecting on Lewis 1974 regarding areion he found all Burks
types to be dark brown on the entire notum rather than mars
orange, as stated in Burks 1953, and synonymized it to
interpunctatum
then
to
the
interpunctatum
complex.
Also
regarding DNA Jeff Webb told me they did not include Travers
samples as they would have been too old and degraded for the
2012 DNA paper. As it stands there are 15 Bins, or clusters in
the genus. It will take an NC worker to go back to the type
location site and do a rearing study, and compare with the
Cornell collection, to create clarification. Dr James H
McDunnough first described heterotarsale February 1933, and
Traver described affine April 1933. Most of the heterotarsale
described are from Illinois from around 1927 and Ottawa Ontario.
The earliest collected affine was April 1930 so priority goes to
heterotarsale.
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With only 6 collection sites for affine little was known.
However today with altitude and ecology they are very likely
differences in the mouthparts of the larva. Just using Bronte Ck
in the form ohioense dark and light types there are mouthpart
modifications for dietary differences. The darker samples came
from 720 feet with high levels cladophora algae nearing 60% of
the square footage, and at the 350 foot range the cladophora
algae amount drops to near 20%.
Our gut content studies agree with McCshaffrey & McCafferty
(1986) having a gut content of mostly minerals and debris at
300-400 feet. However our dark form of ohioense from the upper
areas gut content for cladophora algae was very high, with
minerals and debris present, concluding they are opportunistic
feeders as stated by McCshaffrey & McCafferty (1986). However as
seen in the rearing tank with cladophora algae they can act as
scrapers.
Regarding affine and heterotarsale there is still differences in
them especially size. But with this new mapping technic there is
some other things to now be considered and that is altitude
which constitutes different ecology, geology, and dietary
differences similar to Bronte creek.
The higher the elevation the faster the water moves, and the
closer you are to natural spring water. Using Bronte as a
benchmark. In its upper altitudes it is dark with a very high
(DO) with water moving in speeds likely in excess of 40 mph.
Therefore the sized of the environment that Stenacron can live
in shrinks and populations go down. This also explains why most
photographed samples come from elevation ranges of 250-800 ft.
The highest altitude species is carolina having the highest
elevation within 5 miles of mount Mitchell NC at Bear gap Black
mountain with the collect site about 4400-5200 ft, mount
Mitchell is at an elevation of 6609 ft the highest of the
Appalachian Mountain range.
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Affine;
Affine collection sites NC, Caraway Ck 1424 ft, Sophia 1522,
Uharie Mountain 1153, Spero 1504, and Denton at 660 ft. There is
one site in north eastern WV being Smoke Hole at 1100 ft, giving
an average elevation preference of 1227 feet.
Heterotarsale clearly indicates a preferred range from 250-900
as a base line making about 500 feet a likely average. However I
personally collected my very first Stenacron heterotarsale May
24th weekend 1987 at Lyman Run PA at an altitude of 1614 feet.
We suspect the diets of affine and heterotarsale would be very
different.
Remember just because you can’t see it doesn’t mean it isn’t
there. In other words just because it has not been officially
mapped doesn’t mean it is not there.
Stenacron follow geology and geography they don’t skip spaces
that they can use to thrive in.
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heterotarsale;
including affine in the range
Carolina range
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Anatomy of Stenacron
In this section we will explore the basic anatomy of Stenacron.
Having a good understanding of what you will see, should you
choose to do a dissection is very important. This will enable
you to clearly see and understand the entire dissection process.
Dissection of all the mouthparts is critical for positive
diagnosis in the larva.
However by just removing and mounting the labrum that is enough
to confirm form, providing the labrum has been blueprinted in
this guide. Removal of the maxillae and mandibles is highly
recommended to make further confirmation. The maxillae are the
hardest part to mount they are thin and fragile and great care
must be taken.
Starting at the larva head capsule. We will work from the
ventral or underside side moving upward through the head. The
labium is the lowest part and it is basically the lower lip of
the larva. Next is the hypopharynx which is referred to as the
tongue. Right above this is the maxillae or the lower jaw area.
Moving upward next comes the mandibles which are considered the
upper jaw area. Finally there is the labrum or better known as
the upper lip. Before we go too far if you really want to
understand mouthpart morphology we encourage you to locate and
read, McShaffrey & McCafferty (1986) “Feeding behavior of
Stenacron interpunctatum”.
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In their document they fully explain the mouthparts and their
specific functions; you can locate a free copy at;
http://www.ephemeroptera-galactica.com/mfbib.php
At this website you can also locate copies of everything listed
in the selected bibliographies in the back of this book that are
currently available.
The first illustration is a general overview of the head from
the ventral side. It shows the entire head with mouthparts in
there correct placement.
The illustration below
(1986) for figure (2).
specific. None of the
form specific, they are
was based on McShaffrey and McCafferty
It is a modified variation to be genus
following illustrations are species or
general genus illustrations.
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Maxillae
left mandible
right mandible
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Labrum
As mentioned in the text on the crown of the maxillae there are
pectinate setae combs. Taking a closer look at them on the
maxilla illustration the red arrow is pointing to them. In the
illustration beside it, there are many types of setae combs used
by other Heptageniidae genera. Regarding Stenacron they only
utilized style D on the chart, and are the ones you will see
under dissection.
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All Stenacron appear to have a submedial row of setae that is
divided into 2 distict types. The submeadial row is on the
dorsal side of the maxilla in and toward the medial area see
below. In this row there are typically 10-11 plain setae at the
bottom, the remaining are fibriated or feather looking in
nature. See the setae chart for a closer view of them.
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Close up of the left mandible from the form majus indicating
inner and outer canines, and the teeth to count for diagnostics
clarification.
Lacinia mobilis
can be fimbriated
80
Here is a sample
written is hard to
into the mouthpart
spots for OH-2-RED
dark type.
Stenacron 2020
from my slide set log book typed as hand
read. This shows just how much detail was put
studies. See the Leperod larva changed it’s
ohioense light type, and OH-3-BLUE ohioense
One thing that needs carification is the location of certain
mouthparts. The mandile in most everything is the lower jaw, and
the maxille are the upper parts of the mouth. In some of the
Heptageniidae they are reversed like in Stenacron. Although not
in the normal location a maxille is still called the maxilla and
same for the mandibles.
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We did a very intense study of the labrums of the 11 forms and
species in our geographical range. We hope this will inspire
someone to bluprint the 6 of the 16 forms in the genus we had no
access to like affine. We can conclued that every form can be
identifed by just the labrum with the usage of measurments on a
microscope. Measuremnet A is how far the median robust setae is
from the frontal margin. Measurment B is the depth of the
indenture of the forward margin. All forms have slight variation
in the overall frontal margin shape. All illustarted match in
all aspects to it’s specific form or species. Althought
canadense and true interpunctatum Say are very similar there is
little question that the labrums are very distinct from each
other just by the configuration in the robust setae, canadnse
doesn’t even come to the frontal margin.
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Now with the mouthparts complete we will look at basic body
setae styles. On the following chart not every style on this
chart is utilized by Stenacron. The one mark (“SS”= scale setae)
is the only one Stenacron does not utilize. All the others are
found throughout the body from the labrum to the tail spines.
The ones marked (LAS & AS) are more commonly called robust setae
in most of the modern manuals.
fimbriated
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The most important genus key to Stenacron larva is the gills on
the sides of the abdomen. Stenacron are characterized as having
gills that have a submarginal anal rib and are pointed at the
apex on gills 1-6. Gill 7 is thread like with fine setae and
typically having a single trachea. Here is an illustration of
what gills 1-6 look like up close. The submarginal anal rib is
the part that has a general color of orangey-amber. This rib is
also present on the 7th gill as seen in the illustration below.
All Stenacron we have viewed the 7th gill has fine setae hairs
on them in the posterior areas but are not considered fringed.
Gills 1-6
Gill 7
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Gills and respiration
The tracheation and respiration system is truly befuddling. It
is also very difficult to map out things that are hard to see.
In the larva of true interpunctatum Say this system is
reasonably visible because they are so pale. However we do agree
with Dr Needham 1935 with the usage of a freshly molted larva.
When the larva is creamy the dark gray trachea stands out more
than normal. The biggest problem we had was the time frame to
illustrate the internal anatomy.
All Stenacron in captivity seem the molt between 4-6 am so by 10
am the maculation process is underway making it all that much
more difficult. If we killed the larva the maculation process
was stopped but so was the movement of air in the internal
system. So what needed to happen was we observed them while
living and made notes then composed an illustration that
represents to the best of our ability what we saw as a
composition.
Some parts were very difficult to see as they lay deep in the
middle of the thorax. Some parts are under the pronotum and the
side of the head capsule. The one area where trachea tubes are
very visible is in the rear of femora. We conducted an
experiment several times to see what happened and the result was
the same. If we removed all the gills from the larva including
the 7th gills the larva dies. If we remove all the gills from
the right side the larva will live but struggle. This made me
ask one question. Why? First as a gill is lost in the natural
world the larva grows a replacement at a moderate pace.
We know that both the left and right abdomen trachea trunks are
connected together at the posterial area of the 7th and 8th
Sternites. The primary trunks are dorsal lateral from the 1st
till the posterial area of the 7th. They then grow downwards
quickly to the ventral side. At the posterior-ventral-median
area there is a palmen body at each sternite. In the next photo
there is a ventral photograph of a heterotarsale female larva
that we have marked with red circles.
They are hard to see but inside each circle is a palmen body. We
will place arrows with explanations. All palmen body in the
larva is basically considered a heart. There are 3 in each larva
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the primary one is in the head capsule; there are two more in
the rear ventral areas of the 7th and 8th sternites.
Main trachea trunk
7th Palmen body
8th Palmen body
Palmen body
Main trachea trunk
Forward trachea trunk
We have created a general illustration of the entire primary
trunk system from the 10th segment to forward area of the palmen
body in the head capsule. Ironically in the head the palmen body
and forward trachea trunks reside right under the cranium
suture.
In the following full body illustration the trachea we made the
palmen body much larger than it is in real life so you can get a
better view of it. Marked by an arrow is the primary trachea
trunk that can be seen in the head shot of gildersleevei. The
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other one we call the pronotum trunk as it resides under the
pronotum area and feeds the forward legs from under the head
capsule, while connected to the primary trunk. If you have never
seen nor own The Biology of a Mayfly you would not get to see
this that is part of the reason in attempting to show the
internal workings of the larva.
Primary trachea
Pronotum trunk
This gives you the general concept of the breathing and
tracheation system, and how it is basically configured according
SHU 1935. In the next illustration is an exploded view if the
system in the abdomen.
If you could pull a gill away from the abdomen without the gill
breaking off this is what you would see. The idea is to show how
the gills are attached to the trachea tubes. At the dorsallateral area of each lateral projection there is a small
elevated ᴒ shaped indenture on the dorsal side that the gill is
formed out of called spiracle duct.
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On the next page is a relatively 3D model of the abdomen from
the 7th tergite. The view point is dorsal but looking forward
and up the abdomen. It is an actual cross section and it gives a
clear view of how the 7th gill is attached to the primary
abdominal trachea trunk.
The spiracle duct is amber in color as it is part of the lateral
projection. This also shows you that the ventral side of the
larva is very flat other than where the underbelly meets the
lateral projection. It is also very evident that from a dorsal
view Stenacron abdomens are highly elevated in the median area
and not flat like others in the Heptageniidae family. The palmen
body we made very large so its location is easily seen.
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Moving to the head now let’s look at the trachea system in the
head. First what you are about to see it based on a female
gildersleevei larva that was filmed on video and later dissected
and put on slides.
We studied from Hsu 1932, 1935, Wodesedalek 1912 interpunctatum
Say. The illustration is a section of the center of the head
capsule showing part of one compound eye, lateral ocelli, median
ocelli, antenna, and the entire tracheation system including the
palmen body so easily seen in the head shot below of the female
illustrated from.
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Primary thoracic
Pronotum
Compound eye
Palmen body
Lateral
ocelli
antenna
So now comes my question and we have not found a clear answer to
it. We know that a gill can come off and regrow. We know we can
remove many gills and the larva will live, and we know if we
take of all gills the larva die.
With that said and what we have seen in dissection we believe
there is a (one way valve) like a venous valve in the human body
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to stop reverse flow. It must be at the actual connection point
where the gill connects to the trachea trunk. The distance from
the gill connection point to the Y in the trunk is about .5 mm.
We have never seen a valve at the Y in the trunk. What we are
saying is when we remove gills the tube valve closes to stop the
intake of water also meaning the system is enclosed and under
pressure. So when we remove all the gills did the larva drown or
did it suffocate by not having any gills to separate the oxygen
molecules.
It is an interesting question. To me it seems more reasonable to
conclude our valve theory or the larva would drown losing any
gills. While on this topic just how are the oxygen molecules
taken in. Here is what we have seen in observations of many
Ephemeroptera not just Heptageniidae. The flat gill plates are
actually hollow. There are two layers that trap the internal
trachea. First gills 1-6 are basically the same but range in
size and look like this illustration below. The gills actually
have to different functioning trachea systems. There is the
trachea that is inside the main flat part in between the two
layers.
Then there is the fimbriated gills section, or hairy looking
ones on the bottom with trachea inside. When against the abdomen
the gill plate covers over the very fragile fimbriated trachea
as this is on the ventral side of the gill plate. We on many
occasions have viewed the gills as inflated like a balloon. One
document we read showed on an electron microscope scan that the
lamella or gill plates are in fact covered with tiny and very
microscopic setae hairs that are typically short and curled
over. This clearly suggests they are there to separate the
oxygen molecule from the hydrogen molecules.
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The lamella layers are bound together at the outside seems all
around the gill except for the connection area to the trachea.
This acts like a sack or bag and are commonly semi inflated with
air. I have actually seen air bubbles trapped inside a gill bag.
From what we understand the lamella is a permeable membrane that
oxygen can pass through to the primary trachea between the
lamella plates. It is therefore a reasonable deduction that part
of the oxygen intake is by this method. However Eastham 1937
suggest that the lamellas are there to pump oxygen over the
fimbriated gills which we agree makes sense. Why protect
something that is of no use, they must draw oxygen to.
Now comes an even bigger question. What happens to the argon and
CO2 gasses created by breathing? In most living things the
respiratory system is a principally a closed system other than
the point of intake and exhaust. So where does the waste go?
Maybe it is disposed out through the fimbriated trachea?
Now that can’t work either or it would interfere with and alter
the intake of the lamella plates. We have spent 100’s of hours
watching the larva and have never seen them produce even one
exhaust bubble. So where do the gasses go, or does this now pose
another huge question. Does the larva somehow recycle the gases
as part of the excretion process?
One think is clear from Wodsedalek 1911 interpunctatum nymphs
are very phototaxis when CO2 is intermixed into the water, they
flee with distress. This to me clearly states the exhaust of
argon and CO2 cannot be near the gills or they would be highly
reactive to it and morphologically it makes no sense.
With this question we have read though the following to try to
locate an answer; Marshall 1927, Kluge 1994, 2004, Wodsedalek
1911, 1912 A, B, C, Ide 1935, Hsu 1935, Eastman 1937, Wingfield
1939, Landa 1948, 1969, and Fink 2008. A lot was learned from
these papers but no one has a clear answer about the Argon and
CO2 discharge. In recent days we collected a very small 3.5 mm
Maccaffertium larva that had just molted that has some
interesting features that can help bring a better understanding
to the question.
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There is one thing very evident in Landa 1948 table 2 figures 2;
the trachea system is connected to the entire digestive track.
This is also seen in all his figures in both 1948, and 1969. The
trachea is also connected to the ganglionic nervous system at
the 3 primary divisions in the thorax.
In recent days we have photographed the 7th tergite divisional
trachea that connects to the Malpighian tubules and the exoliner
of the ileum valve. Looking at the configuration of the trachea
Y at the each spiracle tergite duct the primary air flow is
pointing to the rear area.
With that said we now believe that the oxygen enters trough the
gill plate’s heads back to the 2 rear palmen bodies, and from
there directly enters the main blood vessel or artery and heads
to the primary palmen body in the head for full body
distribution. Looking at this photo of the 6th gill connection
point this clearly indicates air flow to the rear.
One other interesting thing is unlike an animal there is no
visible micro arterial or venial system. There is one primary
trachea trunk system, and one primary artery system. This is
highly suggestive of reabsorption of waste back into the body as
there is no point of discharge other than the anus.
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Moving over to the gills for a minute this every young
Maccaffertium collected also states one evident thing. The
fibrilliform parts of the gills are not the primary of the
intake system the gill plates are.
How can that statement be made? Simple in this 3.5 mm sample
that was alive there are no fibrilliform trachea present see
below photo. There is a very minor branch or root on some gills
in the developmental state but not enough to generate the oxygen
needed for life see first picture dorsal view of 5th gill.
We were also able to some degree photograph the very fine setae
covering the dorsal side of the lamella plate or top of the
plate in the second photo @ 1200X. It is not very clear so an
illustration is also made to indicate these very fine curled
setae hairs we saw in a document.
Fibril gill stump
Setae on the gill plate
So far as it stands Stenacron, Ephemerella, Maccaffertium,
Stenonema, Paraleptophlebia all have an elliptical breakaway
joint where the gill connects to the trachea. It is commonly
amber and often connected to the anal rib.
As the trachea extends from the Y in the trunk heading for the
gills it flattens out a bit and becomes elliptical in shape in
the entire genus above.
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This cuticle connection point is also bulbous. The trachea tubes
themselves are in fact coiled strands that are in pairs with a
membrane connecting them as they form a long slinky like tube.
Actually these strings are more link DNA chains that intertwined
in the artery wall exoliner there are 3 or more chains that make
up one line in the coil see illustrations and photographs.
The illustration below is a view of the exoliner of the artery
showing the chain like strains that are coiled to form a tube.
They also have crossbanding patterns that are longitudinal
forming a matrix fabric like membrane.
Artery exoliner
600X
DNA type chains
2500X
Membrane
DNA chain like
In the trachea the pair of strands are more like the complete
trachea tubes. They seem to be hollow but bound by a membrane.
Then they are bound to each other by the visible membrane that
holds the spiral tube together as a long flexible tube for
longitudinal flexibility. We have noticed in areas in the thorax
the tubes are reinforced at the unions with longitudinal cross
members appearing similar to the artery exoliner seen above with
a slight amber color.
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Trachea tube;
Hollow tubes
600 X
Membrane
When we look at the tube as a solid psychical element the two
tubes together appear to look like only one rib spiraled around
covered with a clear film. Microscope objectives can be a bit of
a barrier as the field of view and light with a 100X objective X
10X eyepieces it is very hard to clearly see things.
We find it is more effective to use standard 40X or 60X
objective and bring the eyepiece strength to 25X or even 30X
when viewing fine details. My new 8 Megapixel CCD camera out of
the box seems to be preset at about 25X. It is not calibrated
and once we calibrate it we may lose the magnification range we
have that is allowing us to photograph down to 2500X. When you
go down that far you get to see things you just can’t see
otherwise. An example is the DNA like strings that makeups each
strand of the spiral exoliner.
2500X
DNA like chain links with membrane
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Let’s look at the gills now and what we see and just how the
gills might actually function. First is a flat illustration of
gill # 1 from a Stenacron then a 3D view showing the trachea
entering the “gill-bag” two layers with trachea trapped in
between the layers?
The layers are referred to as lamella. We wish we could relocate
that electron microscopic gill scan document so we could cite
it. What we have done is illustrate what the scanned image
looked like.
Ventral fibrilliform gills
Internal trachea
Anal rib
Dorsal lamella
Now the same gill except we are inflating it partway between the
lamella plates. You will notice that the internal trachea is
actually attached to the ventral lamella but on the inside. You
will also right way notice that the trachea as it enters the
“gill-bag” there is an oval bulbous area that is amber in color
and there is a special muscle attached to it. Then the trachea
breaks into many primary internal branches.
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Dorsal lamella plate
Bulbous valve
Ventral
Internal trachea
Anal rib
Trachea tube
Ventral fibrilliform gills
Now let’s look closer at the dorsal surface and what we would
likely see at about 3000X or more based on the electron scans.
First is a look at a small patch of these setae then what a
curled setae looks like.
Now we can start to conclude the function and foundation of the
gills. First our 3.5 mm Maccaffertium without fibrilliform
ventral gills states that they are not the primary source of
oxygen or the larva would not survive, and if the fibrilliform
trachea were more important they would surely metamorphically
develop well before the plate gills.
This next illustration is just how we think it happens. We have
many times seen the lamella plates that form a “gill-bag” be
partly inflated and with micro bubbles inside. We have also read
that the lamella plates are permeable. Here is a photo of gill 5
of a Stenacron larva with the gill-bag inflated while alive.
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Space between
plate surfaces
Anal rib
We now believe that the curved setae attract the oxygen
molecules and separate it from the hydrogen. It is looking like
they capture them, collect them on the surface and they are
broken down to a smaller sizes and drawn through the lamella
plate on the dorsal side to the internal trachea.
Dorsal permeable lamella plate
Oxygen molecules
Internal trachea
Ventral lamella plate
This is looking like a very plausible explanation but it still
leaves several points that are not explained. First is the
question that started this adventure, then there is the exhaust
factor of the argon and CO2. What we now feel is there is a one
way valve at the trachea joint at the gill. We are now starting
to see that there is a diaphragm plate inside the trachea in the
center of the bulbous joint.
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There is also a special muscle in the spiracle duct connected to
the bulbous joints. The bulbous joint is also connected to the
anal rib cuticle via muscles. Therefore we are concluding that
when a gill breaks off the elliptical bulbous joint with
internal diaphragm collapses in on itself to seal the end of the
tube.
This
would
instantly
blocking
water
from
flooding
the
tracheation system thus allowing the larva to live and regrow a
replacement gill. The other fact to include is the tracheation
system is an enclosed system therefore it would have an internal
vacuum circulation function. This vacuum would help suck the
closure of the elliptical bulbous joint.
Landa clearly indicates
that the tracheation system is
completely connected to the intestinal track from the entry
point of the esophagus to the anus track. There is also many
trachea forks that connect to Malpighian tubules which are part
of the excretionary process this is evident in Marshall 1927.
Here is a photo we took of the connection points of the trachea
to the exoliner of the ileum valve and the Malpighian tubules.
Now to get a better understanding of this photo we need to start
out looking at what you are seeing farther away than zoomed in.
The first photo below is the end of the stomach coming into the
ileum valve then becoming the colon.
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ileum valve
colon
anus
intestine
malpighian
tubules
Trachea tube
Now let’s look inside the ileum valve to see just how it pushes
digested elements into the colon as a one way valve. There is
also a valve like this called the esophageal valve at the
frontal of the esophagus.
Now here is a photo of the trachea connecting to the malpighian
tubules and where they connect to the ileum valve exoliner. The
trachea connects but can also pass right through the base as
seen in the photo.
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102
With Landa and
in the forward
the connection
area as part of
Stenacron 2020
what we see here the most logical conclusion is
or thoracic area the oxygen is likely used from
points from the esophagus to the rear intestine
the digestion process.
From the ileum valve to the anus we now believe that the argon
and CO2 are reabsorbed into the digestion track and aid in the
clearing of the excretion process there by not interfering with
intake at the gills but also aid the dietary process and keeping
the tracheation process as an enclosed system.
Before we move on let’s look at what we are calling the “Bulbous
joint” at the attachment of the gill of a Maccaffertium and what
might be the diaphragm inside.
Muscle for joint
“Bulbous joint”
Possible internal
Diaphragm
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As we progress with technology and with more advanced study
comes more questions, more answers, and clarity of past work on
internal anatomy. In recent days we have learned that the
illustration by Hsu 1935 in The Biology of Mayflies is in fact
not just the genus. Stenonema in general it was actually based
on an interpunctatum Say, making it an illustration representing
a Stenacron larva, figure 1 plate VII page 39 for the trachea
system. Our current anatomy studies now indicate that this
illustration was likely more broad as it does not properly
reflect the genus Stenacron actually; it is closer to
Maccaffertium.
The first problem was any easy error made by YIN-CHI-SHU 1932
and then 1935 or shall we say miss interpretation as there is no
primary trachea in the anterior area of each femur as he
illustrated. The other is the primary thoracic trunk. Here is
his illustration from his 1932 paper figure 1
1
We have not yet viewed a Stenonema femoratum to clarify but as
it stands this multi part trachea system illustrated in the
thorax are not correct. All Stenacron and Maccaffertium have a
large single tube that travel very near the primary artery from
the first tergite to the palmen division into the head capsule.
The other problem with his illustration is the location of the
fore femora. In Stenacron they come out from under the head
capsule making trachea more difficult to see. All Stenacron the
fore coxa is located at the anterior area of the pronotum making
the median area of the femora appearing to come out from just
behind the compound eye. Now here is our illustration.
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Now the next problem he illustrated in the femora a in and out
of the trachea system and that too is not the case. That makes
it appear like the air/blood/protein mix goes in and the waste
is returned. We have solved this misunderstanding there is a
channel in front of the femora where the tibia can rest as seen
in our next illustration.
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This explains his simple error but also adds to our hypothesis
of reabsorption. So these femora drawings with removing SHU
illustration that the trachea in all appendages is to aid in the
growth that eventually makes all internal mussels so large they
eventually molt. Now another possibility in the evacuation
process is that the of gasses might become a silky membrane
barer to help the new stage emerge with ease.
The next area to cover is the lateral projections and how they
relate to the protection of the gills. Years back I was studying
Epeorus plueralis larva a noticed that the projection is much
more than a sharp spike in fact depending on the view it was not
sharp at all. It is in fact a flat shield with a rounded end.
The following two E plueralis illustrations clarify the value of
the projection.
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Here we clearly seeing what looks very sharp from the ventral
view are in fact a rounded plate. On the subject of lateral
projections the first document we know of that teaches the
method of classification of lateral projections is Bednarik and
McCafferty 1979 Biosystematics Revisions of the Genus Stenonema.
On page 3 they clarify how to measure to insure that your
projection qualifies to be a projection. This system is
excellent but not of any concern regarding Stenacron. All
Stenacron in the genus only have two lateral projections that
meet the scientific criteria. These are the 8th and the 9th. If
you are reading older documents you will hear that all Stenacron
actually have a projection on all 10 tergites. All of them are
minute and undersized for qualification criteria but are still a
projection to protect the gills. One thing we have learned is
the more questions we ask the more questions we have.
Moving over to other parts of interest. All Stenacron we have
observed and mapped out all have the following. In the medianapical-dorsal area of each femur, there are single long paddle
setae.
It is often accompanied by other smaller paddle setae on the
rear femora, but often singular on the middle and fore femora.
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It is still unclear if this is a key to genus and or species. We
have mapped out 10 forms out of the 16 in the genus, and all of
them have this lone long paddle setae present.
There also are 4 distinct groups having related setae patterns
composed of robust and short paddle. On true interpunctatum Say
this singular setae is never accompanied by other setae.
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The distinct groups are; Species concepts, containing all valid
species concepts other than true interpunctatum: the canadense
group; the ohioense group; and by itself is true to form
interpunctatum Say.
Interpunctatum / conjunctum middle femora
Interpunctatum / proximum middle femora
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Other area’s that requires more study and we hope our work
inspires others is the subanal plates of males and females.
Looking at the larva only you can see we were doing a massive
amount of odd and interesting studies on the genus this one we
wish we had of spent more time on. The larva and adults have
consistence in forms and species with the shape of their subanal
plates.
The Subanal plate is the posterior margin of the ventral side of
the 9th Sternite that overlaps the 10th segment. Each form and
species seems to have distinct shapes.
For example look at the following 2 venter illustrations and the
shape of the plates. As you will see size and shape variations
in the lateral projections.
The first illustration is the form and one day to be species
heterotarsale, notice the shape of the subanal plate but the
equal length of projections and the shape of the 9th projection.
The one on the right is candidum.
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Not only are there differences in the shape of the projections
there are differences in the shape of the indentures of the
Subanal plates, but also the radius of the lateral area of the
plate. Now we will look at some sample from the microscope. The
photos are not the highest of quality but we can still see
different shapes.
Conjunctum flat bottom
Interpunctatum Say
soft indenture
frontale minor indenture
canadense
almost no indenture
These Subanal plates’ configurations follow into adulthood. Both
the male and female adult subanal plates match in all we viewed.
This was another aid in matching females to males for positive
identification. This we believe warrants more investigations.
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You can see by the magnitude of our study. Our time was spent in
many places, but very honed in on things that needed the most
work like mouthparts. As far as maculation the larva are very
reliable in their markings. On the next page we will look at
foreleg maculation patterns.
Each form or species has its own maculation pattern. We
unfortunately didn’t spend much time on this but it is worth
pointing out.
These are candidum, heterotarsale, and proximum and form and
species samples will align with the illustrations and often very
closely.
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Another experimental study we did that seems to hold up is also
one we never put much time into. In the larva stage the dorsaltergite
has
unique
spine
posterior
margin
of
the
7th
arrangements. We only mapped out 3 forms and compared them to
multiple samples and they seem to be constant to form. We hope
this might inspire interest for someone else in the future.
Forms mapped out are; heterotarsale, majus, and proximum.
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Regarding the light type and dark types there are other minor
variations in mouthparts. One of the minor differences we
photographed under the microscope. It was OH-2-RED larva, and
OH-3-BLUE larva exuvia of the right labium palps. This oddity
was not restricted to the left or right but rather both sides
regarding variation of form. There is some type of strange teeth
on the ventral side on the dark type, and plain setae hairs on
the light type, see red circles in photos.
OH-2-RED; ohioense light type
OH-3-BLUE; ohioense dark type
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At this point we are leaving the anatomy of the larva so it’s
fair to say we should finish with the emergence process of
leaving the larva and becoming an adult. This is not an easy
stage for the insect mortality rates in captivity are in our
studies about 20%. In the real world floating in the surface
film for too long is not a great idea as you are likely to
become a meal. There is no average time that we can find but we
have seen up to 3 minutes to evacuate the exuvia. Often times in
40 seconds it just depends. The process of evacuation is
multiple stages of suture ruptures in the exuvia. Before we
start the sample used is a male proximum light type and it was
reared and dissected. You will see two pictures both are the
same. However the first it is marked in colors for step by step
explanation. The second is unmarked so you can learn to look for
these things yourself.
Stage one is hours and in some cases a day before evacuation
takes place. Stage one is the separation on top of the
[notum/thorax] on what we call the longitudinal suture. As you
can see there are two red lines. The reason is in the photo the
longitudinal suture is already cracked open. The space in the
center area is the notum of the soon to be subimago stage
underneath. In our observations we now believe that all
Stenacron crack this suture early by many hours. It is our
feeling that they do this to allow water in between the exuvia
and the subimago skin. Water in between would act as a lubricant
between the two surface areas reducing surface tension.
This longitudinal suture remains cracked open for hours prior to
heading for the surface. The next stage is the head deformation.
The head capsule becomes highly elevated in the vertex area like
someone is squeezing the head from the sides inward. They then
start to point their head downwards on about a 40° angle and
hold that position for most of evacuation period. Once on the
water surface with the head pointed down the cranium suture
starts to break this is the orange line. It will start the crack
not at the back of the head capsule but right above the brain
and forward of the palmen body.
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Next as this is taking place the pronotum median suture breaks
away this is the yellow line. At that point the transverse
sutures the blue lines start to break away. Now the longitudinal
suture breaks far apart and past the scutellum to the 3rd
tergite or segment. Now the head tills to about a 60° angle the
cranium suture ruptures all the way to short of the lateral
margins of the head capsule. The head pops out then the pronotum
and transverse sutures break far apart in the front the wings
start to come out. It seems to us at this point there is some
kind of muscular pull from the underside of the thorax. The
forewing wings are not strong and at this point there is a
massive force in play like a pull from the underside. The
longitudinal suture becomes ¾ the width of the entire larva’s
width very fast. The longitudinal suture breaks to the 4th and
sometimes 5th tergite and the adult wiggles out. Even the legs
hang back and slightly under the thorax.
The
following photo is from our other rearing study on Maccaffertium
mediopunctatum and we hatched one in a petri dish in a photo
session by chance. They hatch very similar to Stenacron. This
will give you a better look at what they look like in the
evacuation process.
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Larva under the microscope
interpunctatum / canadense
Female larva from Bronte creek watershed
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10 – 8 tergites
tenth tergite
7th tergite
9 – 7 tergites
Female head capsule
pronotum
Subanal plate
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interpunctatum / conjunctum light type
Male larva from the Bronte creek watershed in southern Ontario
conjunctum-2-pink slide set (2014)
10th – 8th tergites
8th – 6th tergites
10th – 7th tergites
7th – 5th tergites
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6th – 4th tergites
4th – 1st tergites
3rd – 1st tergites
head capsule
Pronotum
middle and hind femora
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Single long paddle setae on middle femora
Round Subanal plate
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interpunctatum / conjunctum dark type
Female larva from the Bronte creek watershed in southern Ontario
STC-1-blue slide set (2014)
10th – 8th /
10th
= projections
9th – 7th tergites
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8th – 6th tergites
6th – 3rd tergites
Head capsule
7th – 5th tergites
4th – 1st tergites
pronotum
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Pronotum and notum
fore femora
Middle femora
9th and 8th lateral projections equal / Subanal plate
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interpunctatum / frontale
Male larva photo plate
10th - 7th
8th – 6th
pigment deletion 8th
7th – 5th
Head capsule
Pink stripe
6th – 3rd
pronotum
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Frontal margin pale spot
10th – 8th
8th – 5th
fore femora
subanal plate
pleura streaks
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interpunctatum (Say 1839)
Male larva from Bronte creek watershed in southern Ontario
ST-3-BLUE slide set 2014
10th – 8 tergites
5th – 3rd tergites
7th – 5th tergites
Subanal plate
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9th – 8th = projections
Pronotum
head capsule
mesonotum
interpunctatum / proximum
Male larva from Bronte creek watershed in southern Ontario
ST-2-RED slide set (2014)
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Ventral view
10th – 8th tergite
7th – 6th tergites
8th and 9th 8 is shorter
8th – 7th tergite
6th – 5th tergites
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5th – 4th tergites
4th – 2nd tergites
Male head capsule
4th – 3rd tergites
3rd – 1st tergites
pronotum
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Mesonotum
scutellum
Frontal margin pale spot
Middle femora
median ocelli pale spot
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Middle femora showing long single paddle setae
10th – 8th Sternites
8th – 9th lateral projections
Subanal plate
8th – 7th Sternite
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Larva Heads
female
female
male
male
female
female
male
female
female
male
female
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Photo Plate Larva
All samples except last 2 photos and the female canadense all
were
reared
to
adulthood
giving
clear
indication
and
identification. The retracing from the larva exuvia made
identifying live larva relatively easy. Stenacron from a
maculation standpoint in the larva stage are quite consistent
within form.
Travers table 1935 indicated lateral projections as a key. Our
studies agree and confirm this lost key to larva. We mapped out
multi samples of larva to get an average tooth count per form
which is found in the tables in the back, we also blueprinted
the labrums of 10 forms showing identification of the 10 form by
just the labrums alone is now possible see that section.
We will start this photo plate with the very first photos of
Stenacron gildersleevei. Even Lewis 1974 was unable to offer
quality photos of this species. Not only are we offering photos
we filmed a video of a live female larva under my microscope.
Stenacron gildersleevei has a very district feature not seen in
any other larva in the genus we reviewed. From right between the
lateral ocelli in the head capsule there is blood red fluid
being pumped from the 4th gill to center of the head. We saw
this in 8 gildersleevei samples. All gildersleevei larvae had 13
pectinate setae combs on the crown of the maxilla.
So we will start this photo plate with this species. On the link
above the screen shot you can search out and watch the live
video showing strange red fluid.
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Stenacron gildersleevei female larva alive on video
https://www.youtube.com/watch?v=ZqbXHDLAGhc&feature=youtu.be
Stenacron gildersleevei female larva
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Last photo of gildersleevei
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Male interpunctatum / majus
Female interpunctatum / proximum
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Female interpunctatum / majus
Female candidum
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Female heterotarsale note the median line
Female heterotarsale ventral view
You can see the deep indenture of subanal plate
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Female interpunctatum / conjunctum light type
Female interpunctatum / conjunctum dark type
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Male True interpunctatum Say 1839
Male True interpunctatum Say 1839
True interpunctatum Say 1839 has little to not markings in the
way of banding on the legs very pale toned. If you look close
enough you can see these are two different samples clearly
indicating leg maculation.
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Female interpunctatum / ohioense light type
Female interpunctatum / ohioense dark type
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Female interpunctatum / canadense
Female interpunctatum / canadense
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Male interpunctatum / proximum light type
Male interpunctatum / proximum dark type
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Female Stenacron; 1; majus
heterotarsale
2; proximum
5; ohioense LT
3; canadense 4;
6; heterotarsale
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None of the following were reared by Sharon.
Sharon Moorman; Stenacron carolina lake Norris TN
Sharon Moorman; frontale lake Norris TN
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Spots in front of median ocelli
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Head Capsules
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3D lateral views
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General Top Views
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canadense
interpunctatum Say
canadense
venter
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Heterotarsale
proximum
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ohioense light type
ohioense dark type
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conjunctum light type
conjunctum male dark type
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conjunctum female dark type
affine
based on Travers 1933 description
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majus
frontale
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gildersleevei
candidum
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minnetonka
pallidum
based on Lewis 1974 and entire genus study
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carolina
floridense
based on Bold Systems collection
based on Bold Systems collection
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Labrum Blueprints
To show the value of the labrum as a diagnostic tool and not a
key, let’s look at the valid species concept of gildersleevei
and the one day to be valid species of heterotarsale, and just
how different the labrums are.
The first thing that stands out is the size and shape of the
frontal margin with regards to the indenture. Next the entire
posterior-sublateral area around to the forward margin shape is
very different. There are distinct differences in the posterior
ligaments see red arrows.
Even the accordion like muscle tissues between the left and
right ligaments varies in the forms and species with regards to
the range of extension in and out. Next are the ventral robust
setae spines working from the median spine to the lateral
spines? Gildersleevei has a single row of 6, followed by 8 rows
of 2.
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On the heterotarsale sample it is only a single row of robust
setae. On the dorsal side the setae hair density is different in
configuration and in its placement. On the lateral right dorsal
area on the heterotarsale there are sporadic fine setae.
On the gildersleevei there are 4 well spread out extra-long
course setae not coming to the median area, and both having
lateral margin setae. It is also important to note that each
species and or forms have their own head capsule shapes. We
never attempted to illustrate the different shapes but candidum,
ohioense, proximum, all have different head capsule shapes and
they reflect the shape of the forward-indenture and forward
margin of the head capsule and labrum. Within form the only time
there is variation in the labrums of the dark type verses the
light type of the same form. This difference is so minor that we
only did the ohioense light and dark type to show the minor
difference as an example of variation in form.
However when it comes to the maxilla and the mandibles there is
a big difference. Example ohioense light mandible has 6 teeth on
the innerside of the outer canine, and 0 teeth on the innerside
of the inner canine. The ohioense dark type has 7-8 teeth on the
innerside of the outer canine, and 3-4 teeth on the innerside of
the inner canine. Based on our obersvations of the form
ohionense dark type late at night in the rearing tank a diet of
claudaphora algae was highly prefered.
This also seems to align with a need for more teeth to
properally process the algae. There is also an increase in the
amount for pectinated setae combs on the crown of the maxilla,
and fimbriated setae in the submedial row. While viewing the
dark type Ohioense. The
light type ohioense,
proximum,
conjunctum, proximum, majus all tended to prefer the lose debria
at the bottom of the tank. Ohioense dark commonly left a trail
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in the algae as they scaped their way onlong on the glass.
Ohioense dark comes from a dark substrate with lots of
claudaphora algae. The lighter type is 3.9 mile down stream with
heavier sedimentations and lighter amounts of claudaphora algae.
Clay sedimentation saturation suggests a mineral and debria diet
as per McShaffery and McCafferty 1986.
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You will notice on every blueprint there is a coding number
system. The proximum right above says [PX-3-yellow dot] that is
my slide set numbers and color coding so we could keep track
when we were comparing multi samples at the same time to insure
deviation for the blueprints. This was also a slide set filing
system so finding a set was easily done.
We would really like encourage someone with collection access to
review affine Traver 1933. It is very likely that because Traver
synonymized affine to heterotarsale 1935 as per doctor Needham
that nobody has examined the former species since. Spieth 1947
lightly discussed it and we think he saw the samples that have
been at the Cornell collection since 1933. We are not even sure
that larva or larva exuvia exist in the collection. Because DNA
states heterotarsale should at some point be a valid species,
affine will need to be re-reviewed. There is distinctly a size
difference in the two; as well she also never illustrated the
male genitals. At the closing of this book we were able to
dissect and photograph the labrum of S Carolina showing a row of
6 robust setae followed by a group of 3 then random ones all at
the frontal margin.
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Comparative Discussions
In this section we will compare the larva. Until this guide
little was known about the larva stage. The larvae as far as
maculation goes are reliable for consistency in their patterns
and trends. Some species have never been seen before, and
illustrations of those species or forms were created by
descriptions and morphological studies of the entire genus, to
give a good overall facsimile to work with.
A new diagnostic tool has come out of intense rearing and larva
mouth morphology studies. The labrums of all larvae are
consistent and should be viewed as a valid tool to identify
larva. At this point only larvae that we collected have been
mapped out with a blueprint of the labrum and can be used this
way. Dr Jeff Webb has stated this is not a key as it is not
dichotomous. It is however a remarkably accurate form and
species identification tool.
There are currently 6 forms out of the 16 in the genus that we
have not blueprinted. Everywhere this new tool can be employed
it will be shown and described in this section of the guide and
elsewhere. There is a section just on the blueprinted labrums in
front of the general descriptions.
Currently as of 2017 the species and forms that are not mapped
out are as follows; affine, areion, carolina, floridense,
minnetonka, and pallidum. Some of these are not in our research
areas of southern Ontario and therefore access to samples is
difficult to obtain.
Some of these forms may never be mapped out as few samples exist
in any collections being affine and no larvae exist for areion.
Another important key is the lost key. The lateral projection
length of the 8th verses the 9th are reliable to all known forms
as per Traver 1935.
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larva verification table
This is a basic replica of Travers 1935 table. We have added
interpunctatum Say as new information was available from current
collections. This version is modified with numbers on the top rather than
abbreviations. Anywhere this table could be updated we have done so and
have marked it by highlighting.
Species or form
Affine
Areion / unknown
canadense
candidum
carolina
conjunctum
frontale
floridense
Gildersleevei
heterotarsale
Interpunctatum *
majus
minnetonka
ohioense
pallidum
proximum
1
♂-♀
7-9
7-9
10-13
8.5-10
10-11
8-10
8-10
8-10
11-13
9-11
7-9.5
10-12
8-10
10-13
6- 7.5
9-11
2
N
-N
N
N
N
Y
Y
N
N
N
Y
Y
N
N
Y
3
Y
-Y
N
N
Y-N
Y
N
N
Y
Y
Y-N
Y
Y-N
Y
Y-N
4
5
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
N
N
N
N
N
N
N
Y
N
N
N
N
N
Y
N
6
(8th is)
equal
unknown
equal
shorter
longer
equal
equal
unknown
equal
equal
equal
equal
unknown
sub-equal
Shorter
shorter
1; Body length is expressed in millimeter (♂ is the smaller number)
2; Median pale spot on the frontal shelf of head capsule.
3; Continuous pale submedial streaks on abdomen.
4; Ventral markings on the lateral areas of the abdomen.
5; Posterior edge of tergites dark or blackened.
6; Later projection of the 8th VS 9th for spine size.
Note regarding column 3; there is new evidence of geological variations. When they effect
the table they are noted as Yes and No mean that they have both continuous and
discontinuous stripes. Note; there are no records for lateral projections for any new
species after Travers 1935 table. So minnetonka and floridense are unknown, and areion
was never collected in the larva stage.
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Below for the first time we can see two forms that are very
confused when not side by side. The two below are true canadense
on the left and true interpunctatum Say on the right.
Here it is easy to see the differences in them. We will look at
the larva from a dorsal view of the abdomen, and the pale
maculation mark directly in front of the median ocelli on the
head capsule. Both are reliable and useful to aid you in coming
to a reasonable conclusion of form, which in turn will bring you
to valid species status prior to dissection.
In order to come to positive identification for all larvae they
must be dissected and matched to the tables provided in this
guide. Dissections of the mouthparts are the only keys to
distinguishing them from each other than size, maculation
patterns, and the lateral projections.
Lewis 1974 The Taxonomy and Ecology of Stenonema Mayflies really
made leaps and bounds to establish mouthpart taxonomy in the
different forms. Rearing and researched filed in the blanks of
the past 5 years.
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(Stenacron interpunctatum / canadense)
(Stenacron interpunctatum) true (SAY)
Clemens (1915) clearly impressed that there is little to no
difference in the larva of these two, and that canadense should
be viewed as a larger form of true interpunctatum. While this is
reasonably true for the larva stage there are some very reliable
and consistent markings to separate them in the larva stage
besides their physical size.
Starting with the heads of these two, here are some head shots
for them under the microscope at 40X. Although the canadense is
a female sample the pale median ocelli spots are still
consistent between the males and females.
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Looking at the pale spot in front of the median ocelli we can
see the differences in the spots. On the interpunctatum the pale
spot is very large almost connecting to the lateral ocelli pale
markings near the compound eyes. The pale spots on the head
capsule of interpunctatum are larger and the background darker
coloring is paler and there is no midcrania spot on the
interpunctatum, but there is on canadense.
The abdominal continuous submedial pale streaks on all tergites
are wider and more defined on true interpunctatum Say. The
sublateral abdominal spots are a very important feature. In
interpunctatum they connect like the submedial streaks and are
continuous rather than discontinuous as in canadense. The
overall color is paler, and the legs on interpunctatum the
background color is pale hyaline whitish rather than the yellowbrown coloring found on canadense.
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The size is a strong feature interpunctatum male larva being 7
mm and canadense males being 10 mm. Both also share equal length
in lateral projection of the 8th and 9th segments. If we look at
the labrums of these two we can see differences in them.
Here we can see that true interpunctatum Say has a single row of
5 in the median area turning into a double row of robust setae.
On the canadense labrum there is a single row of 4 turning into
rows of 3 then quickly into two rows of 4-5 for the robust
setae.
We can clearly see as in the abdomens above that they are very
similar but yet distinct from each other. They can also be
distinguished from each other by the maxillae. On the canadense
there are 10-11 pectinate setae combs on the crown of the
maxilla, and on interpunctatum there are 9-10.
Canadense
has
25-30
setae
in
the
submedial
row,
and
interpunctatum Say has 25 or less according to Lewis (1974) and
our studies concur with Lewis.
The mandibles are also diagnostic by canadense having 6 teeth on
the inner side of the outer canine and 0 on the inner side of
the inner canine. Interpunctatum Say has 7 teeth on the inner
side of the outer canine and 4 on the inner side of the inner
canine.
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(Stenacron interpunctatum / ohioense)
(Stenacron interpunctatum / canadense)
We have no doubts that Dr Traver erected ohioense in (1935) to
separate it from canadense. Until that time there was a large
amount of taxonomic confusion between these two in the larva in
particular. The adults of these two are less likely to be
confused. Dr Walkers (1853) description for canadense does not
mention that the species has spiracular spots and Traver (1935)
also agrees with Walker.
The first sign of confusion over spiracular spots was Clemens
(1915) where he stated that canadense in the larva stage has
spiracular spots. Clearly he was looking at the light type for
ohioense as it has spots and even today it is hard to
differentiate it from canadense.
Currently there are two types of ohioense larva and both have
spots. One has discontinuous submedial stripes on the abdomen
the other has continues stripes.
See the chapter
details on that.
type of ohioense
that form in the
the leopard larva changed it spots for more
For this section we will only utilize the light
larva as it matches Dr Travers description for
larva stage.
We can see a true difference between them when placed side by
side. Now let’s look at the complete abdomens for these two with
and without wing pads and gills.
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The abdominal view makes it very clear who is who. But even at
that, it can be very hard to separate them. The sublateral spots
are hidden under the gills on the ohioense, and the spiracular
spots are hard to see. However without dissection they can be
separated by two key features.
On the ohioense larva the 8th and 9th lateral projections are not
quite equal. They are referred to as sub-equal by Dr Traver
(1935).
The 8th projection is slightly shorter than the 9th. On average
the difference is the 8th is typically 6-7/100th of a millimeter
at 200X, and the 9th is commonly 9-11/100th of a millimeter long.
Though not a big difference, it is visible under lower powered
magnification.
The second feature to separate ohioense is the spiracular spots
at the lateral areas. They can be hard to define on tergites 69, but on the first through the 6th they are easily seen hiding
within the gills. True canadense will not have spots.
It will however have blackish shading in the spiracle areas. But
this blackish shading is typically only present on tergites 6-9.
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Therefore tergites 1-6 should be void of blackish marking but
may still be darker.
Looking now at the labrum on the ohioense it has a median single
row of 4 followed by 2 rows of 2, then 4 rows of 3 robust setae.
Using this combination (labrums + lateral projections +
maculation)
=
form
and
then
species
under
preliminary
dissections. Further dissection of the maxillae and mandibles
will confirm you findings on any larva.
Looking at the median ocelli pale spots we can see the
difference in the two forms. The larva of ohioense light can be
confused with proximum and that is the next situation we will
review.
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(Stenacron interpunctatum / ohioense)
(Stenacron interpunctatum / proximum)
Confusion of these two larvae is very likely mostly because of
the lateral projection. As discussed above ohioense has subequal lateral projections and proximum has a shorter 8th
projection. They both also share continuous submedial streaks.
We can separate them by two delimitating factors. The labrum is
critical for separation as is the physical size.
Proximum is smaller in overall size. Looking at the full larva
we see how these two are confused without great care.
Clearly too really separate them we will have to do a full
diagnosis. Let’s start at the head capsule. One defining feature
is proximum has a very fine pale pinkish median stripe on the
frontal shelf. Next the pale spot in front of the median ocelli
is quite a bit different.
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The other unique and fine feature is the median crania spot. On
the ohioense this is a very strong feature that transcends into
the adult stage as part of the complete smile or transverse band
across the frontal shelf. In proximum as seen by the red arrow
has very faint shading or no spot at all.
The adults of proximum do not have a true median crania spot but
rather fine gray shading as seen in the larva head capsule.
Looking at the labrums we can see differentiation in the number
of robust setae and their placement.
Another feature of the labrum lies on the dorsal side. The
placement of the fine setae hairs on the ohioense are forward of
the robust spines and on the proximum most of this setae hair
covers over the robust spines. The other interesting feature is
on the proximum the robust setae reach the lateral anterior edge
and this does not occur on the ohioense. Measurement A= will
help you determine between the two as ohioense median robust
spines are set much further back from the anterior edge.
Moving to the other mouthparts to further separate them. The
maxillae of ohioense have 10 pectinate setae combs on the crown
of the maxilla, and on proximum there are 10L–11R. In the
submedial row of ohioense there are 25-30 setae, and on proximum
there are 28-32.
The mandibles are of more help than the maxilla. On the ohioense
there are 6 teeth on the inner side of the outer canine, and 0
teeth on the inner side of the inner canine. On proximum there
are 6 teeth on the inner side of the outer canine, and 2 teeth
on the inner side of the inner canine. Clearly with this
information combined with the fine details they are different.
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The length of the 8th lateral projection on proximum is
considerable. When viewing these two side by side we can clearly
see the difference in the 8th projections. Moving over now to
the abdomens for comparisons. Side by side there is not much to
compare as they are clearly different. One striking difference
is on the proximum the sublateral areas of the 3rd tergite are
almost completely pale which is not visible with the wing pads
present.
Now we will move to compare proximum with conjunctum.
(Stenacron interpunctatum / proximum)
(Stenacron interpunctatum / conjunctum)
These two are extremely similar in the larva and especially in
the adult stages. There are times when separating the two is
impractical. However they can still be defined by some very fine
points.
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The most critical feature in the larva stage is that proximum
has a shorter 8th lateral projection and the 8th and 9th are equal
in conjunctum. Let’s start by looking at the full larva views.
There is also a small difference in the overall size of the two.
Proximum male is normally 9.5 mm and conjunctum is typically 8
mm. The standard geological variation of conjunctum is very dark
grayish black as seen above and proximum is much paler. Turning
to the pale spot in front of the median ocelli. We can clearly
see that they are shaped different but more so are that
conjunctum has a median crania spot that is strong and clear.
This spot also is a strong feature in the adult stage.
Looking at the abdomens there is one feature that clearly stands
out. The submedial stripes on proximum are continuous and on
conjunctum they are discontinuous.
The other interesting feature is the way the submedial stripes
intrude into the 10th segment. On the proximum they are fully
intruded, and on conjunctum they barely intrude past the
anterior edge.
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Notice that the terminal lateral edges are lighter on the
proximum and darker on the conjunctum. While on the topic of the
abdomen we should look at the female conjunctum. Notices on the
male
conjunctum
above
the
submedial
stripes
are
only
st
th
discontinuous from the 1
to the 6 . In the female seen below
they are discontinuous throughout. The other interesting factor
was mentioned by Dr Traver in her (1935) couplets that
conjunctum has a ♦ diamond shaped spot in the median area of the
9th tergite as seen in the illustrations.
♀
It was important to mention this because of the confusion that
could occur if not mentioned now. Backing up now we shall move
to the mouthparts of the two. The labrums of the two are very
close as we would expect see with them having so much in common.
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The most important feature is how far back the robust setae rows
are from the anterior edge in the median area. Notice on the
proximum the robust seta comes out to the lateral areas of the
anterior edge. Also on the conjunctum all the dorsal setae hairs
are set well forward of the robust setae.
In proximum they are almost on top of them. The measurement A=
will also separate them from each other. The other mouthparts of
interest are the maxilla and the mandibles. On the crown of the
maxilla on proximum there are 10L and 11R pectinate seat combs,
and on conjunctum there are 10 on each. In the submedial row on
proximum there are 28-32 setae, and on conjunctum there are 3437 present.
On the mandibles of proximum there are 6 teeth on the inner side
of the outer canine, and 2 teeth on the inner side of the inner
canine. On conjunctum there are 6 or 7 teeth on the inner side
of the outer canine and 1 or 2 on the inner side of the inner
canine. This diagnostic work allows separation of these two.
(Stenacron interpunctatum / frontal)
(Stenacron interpunctatum / majus)
These two are very likely to be misidentified in the larva by
two basic features. They both have a pale spot on the frontal
shelf of the head capsule, and they both share a deletion of
pigmentation in the median posterior area of the 8th tergite.
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Although this deletion is typically very minor in majus. When
both are side by side we see many differences in them. The
deletion is typically very large in frontale as we see in the
full abdomens.
Both have continuous submedial streaks but notice how wide the
median line is on the frontale from the 1st-7th. On majus the
median line is smaller and broken up. Each median section is
typically shaped like a “lens” as noted by Dr Traver (1935). On
the majus there is also an interesting feature not seen in any
other in the genus. Looking at tergites 4, 7, and 9 the
posterior area of the submedial streaks, they flair out towards
the lateral edge from the median areas rather bell shaped.
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The spiracular spots on the frontale are commonly very small and
hard to see, in the majus they are very large and standout as
they do in the adult stages. On the majus with regards to the
posterior of median area of the 7th tergite there is commonly a
slight deletion in pigment of the median stripe as seen above.
This does not occur in typical samples of frontale.
The pale spot in front of the median ocelli is also very
different from each other. However they both share a median
crania spots that transcends in to the adults stage. The
frontale spot is much more of a heart ♥ shape and on majus it is
more or less and T shaped spot.
On the mouthparts the labrum will greatly help to separate them.
The majus has very prominent stout robust setae in a single row
that commonly but not always follows a ridge like fold. This
fold has been found in more than 80% of all larva examined by
us. It is still unclear if this ridge fold has any specific
value.
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On the frontale the robust setae start out as a single row of 5
then become a row of 2. The indenture B= is very shallow on the
frontale and the overall shape is quite different.
Both the
maxilla and the mandibles have separation value. The maxillae of
frontale according to Lewis (1974) are as follows, (and our
studies concur with him). There are 9 pectinate setae combs on
the crown of the maxilla, and there are 9L and 10R on majus.
There are 39-46 setae in the submedial row on frontale and
typically 34-35 on majus.
The mandibles of frontale have 6 or 7 teeth on the inner side of
the outer canine, and 2-4 on the inner side of the inner canine.
On majus there are 6-8 teeth on the inner side of the outer
canine, and typically 0-2 teeth on the inner side of the inner
canine. Both of these forms share lateral projections of the 8th
and 9th that are equal in length.
(Stenacron gildersleevei)
(Stenacron candidum)
These two are very likely to be confused for two very specific
reasons. First there are no known photos of gildersleevei till
now, as we are offering photos of this species in this guide.
The second is both are very distinct from all others in the
genus by their discontinuous submedial abdominal stripes. Here
are photos of gildersleevei for the first time.
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We should look at the full larva views of these two. The first
major difference is candidum is very dark, almost black and
gildersleevei is more of a cinnamon like in coloring. Without
them being side by side it is very difficult to separate them.
But they are very different when we look really close at them.
Gildersleevei is also much larger than candidum.
The very first clue to separate them is candidum has a shorter
8th lateral projection and on gildersleevei they are equal. Now
let’s look closer at their abdomens.
They are really starting to look the same. The first striking
feature is their submedial stripes. They are both quite
discontinuous but interestingly enough both have “vase” shaped
spots.
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What really stands out is the amount of pale areas on
gildersleevei when the gills and wing pads are absent. The most
important thing before dissection to tentatively identify them
is gildersleevei has blackened posterior margins at the end of
each tergite and candidum does not.
Moving on to the head capsules and the mouthparts. The pale
median ocelli markings are similar but different. The mark on
candidum is very triangle shaped agreeing with Burks 1953. The
mark on gildersleevei similar but it is more elongated on
gildersleevei.
The labrums offer a lot to separate them. First is the general
shape they are distinct, but the robust setae is the bigger
clue. On the gildersleevei there is a single row of 6 in the
median area then they turn into a row of 2. On the candidum
there is only a single row of very stout robust setae. The
largest and most significant key is the maxilla. On the maxilla
crown of gildersleevei there are 11-13 pectinate setae comb with
13 as a true average. On candidum there are only 7-8 with 7
being the average. All this should allow complete allow
separation.
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(Stenacron interpunctatum / heterotarsale)
(Stenacron interpunctatum / canadense)
Historically in all books there has always been confusion
regarding heterotarsale. Because DNA to our understanding states
that should in fact be a valid species we should put the spot
light on this form, as one day it will likely become a valid
species again.
The only other larva that can look similar and could be confused
with it is canadense. Therefore we will compare these two. The
very first thing to mention is Dr Travers couplets (1935)
regarding the spot in front of the median ocelli. Dr Traver
noted it as being somewhat in the shape of “la fleur de lis”. We
can say from rearing and dissecting that this feature is quite
reliable as a character feature of this form. We can clearly see
there is a very big difference in the two with regards to this
marking.
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Moving over to the full larva view we quickly notice they are
both fairly pale in coloring, and both have very continuous
submedial stripes.
The first important feature to separate is that canadense has
very wide and somewhat straight submedial stripes on the
abdomen. Heterotarsale has stripes that look a bit like a bell
shapes on each tergite. The median line on the abdomen of
canadense is thin and uniformed throughout the entire abdomen.
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The other interesting maculation character in the median line on
heterotarsale is, the somewhat arrow shaped spots pointing
backward
on
each
tergite.
Another
feature
to
note
on
th
segment has a pale yellow posterior
heterotarsale is the 10
and lateral edge. The other common factor for these two is they
both have equal lateral projections of the 8th and 9th segment.
The mouthparts are also quite distinct from each other. Turning
to the labrums we can see that they are pretty self-explanatory
as they have little in common and not likely confused.
On the maxillae of heterotarsale there are 9 pectinate setae
combs on the crown of each maxilla. On the canadense there are
typically 10L and 11R. In the submedial row of setae there are
between 30-35 on the heterotarsale, and 25-30 on the canadense.
The mandibles are very useful to separate them as heterotarsale
has 5-7 teeth on the inner side of the outer canine, and 3-4 on
the inner side of the inner canine. On canadense there are 6
teeth on the inner side of the outer canine, and 0 on the inner
side of the inner canine.
The physical size is also a factor as canadense is much larger
the heterotarsale. With all the information above confusion
through dissection is not very likely. Without a complete
dissection these two could be confused.
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(Stenacron floridense)
(Stenacron carolina)
These two are easily confused for several reasons. First they
share similar geographical ranges. Second the maculation
patterns of the submedial stripes are very similar on tergites
1-7.
When side by side it is reasonably clear which is which. The
most important feature to separate them is carolina has an 8th
lateral projection that is longer than the 9th. The lateral
projections of floridense are unknown but likely equal in
length. Moving over to the full abdomens for a closer comparison
we see the true differences.
The mouthparts of the two also allow separation. See the table
at the back of this guide for the features and keys that
completely separate these two.
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Now it is time to put on my boxing gloves and fight for the
underdog. It is now becoming very apparent that geology,
elevation, and dietary factors have a large impact on mouthpart
morphology, and that the ecosystems are constantly changing and
evolving as they move down stream. So why would we expect the
insects to not self-modify for these changes.
We can see labrum and mandible modifications in the same form in
a very short distance and elevation change on Bronte. The
pigmentational impacts, slight labrum modification, tooth counts
on mandibles, and scraper like teeth on the ventral side of the
labium palps of ohioense. Surely we can deduce that all
Stenacron are self-modifying in the same way based on their
specific environmental needs.
There is little doubt in my mind that heterotarsale and true
interpunctatum Say share very similar ecosystems and elevations,
and are without any doubt very distinct from each other in the
larva and adults stages. Here is the larva of the two and below
them is an illustration that directly reflects Traver 1933 for
affine.
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There is no question they have very little in common. Both the
heterotarsale and interpunctatum are reared samples and are
confirmed adults to their historical profiles. Looking at the
affine it is clearly more related to true interpunctatum Say.
Heterotarsale and interpunctatum Say share the same environments
and elevation here in southern Ontario. From every photo known
true interpunctatum and heterotarsale clearly cohabitate in an
average elevation of 250-700 feet above sea level. Now moving to
affine it was collected at much higher elevation with an average
of 1227 feet and as high as 1424 feet.
These ecosystems would have little in common. The upper mountain
areas are heavily treed typically State forest with lots of
shade over the waterways. They would be very clean pure water
with high dissolved oxygens making plant growth very high just
like on Bronte Creek.
As the system is coming into the lower elevation the systems
modify in every aspect. Often meandering slowly with fewer trees
for shade making the water warmer. Lower dissolved oxygens less
plant growth, less food for insects. In Bronte in the lower
areas there is no aquatic life at all in some areas. Too much
sedimentation, water warm, and low (DO) equal’s no plants.
All watersheds are built on the very same principals except
human interaction take place more often in the lower areas. We
clear all the trees for houses and shopping malls, and leave
little room for anything else.
We think after reviewing all these interesting facts and having
16 DNA clusters in the genus and affine was not even at the DNA
convention, we truly believe that we all owe affine a second
look.
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Larva Couplets
Key to larva are lateral projections of the 8th VS the 9th for
length as per Traver 1935, they work and are reliable. As per
Lewis mouthparts are diagnostic, and labrums are accurate to
form and species that are mapped out. Lateral projections 8th &
9th.
1. affine; mouthparts unknown, prominent continuous stripes
on abdomen, lateral projection equal, no spiracular spots.
2. areion; larva never collected or reared, unknown.
3. canadense; mouthparts diagnostic, labrum distinct, pleura
streaks
on
mesosternum,
abdomen
prominent
pale
wide
continuous submedial streaks, no spiracular spots, lateral
projection equal.
4. candidum; very dark all over, distinct triangle in front of
median ocelli, mouthparts very diagnostic, labrum very
distinct,
discontinuous
submedial
stripes
on
abdomen,
th
spiracular spots, lateral projections the 8 is shorter.
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5. carolina; distinct T shape spot in front of median ocelli,
mouthparts diagnostic, labrum unknown, abdomen absent of
typical submedial stripes; on the 4th tergite moderate pale
spots, 1-2-3 small pale spots, 5-6-7-8 very small pale
submedial spots, in some samples absent, tergite 9 a pair of
submedial spots, 10th two distinct stripes deeply intruding
into the 10th, lateral projection 8th is noticeably longer than
the 9th the only one in the genus to have this.
6. conjunctum; mouthparts are diagnostic, labrum is distinct,
mesosternum pleura streaks, continuous submedial stripes on
abdomen,
dark
type
discontinuous
stripes,
lateral
projections equal, with spiracular spots, ♦ diamond-ish
shaped spot median tergite 9 as per Traver 1935.
7. floridense; mouthparts diagnostic labrum unknown, abdomen
tergite 1-7 very small pale submedial spots may be absent
on some samples, 8th very prominent submedial spots
connecting having a deletion of pigment in the median
posterial area, 9th pair of submedial stripes, 10th slight
stripe intrusion, lateral projections unknown, Bold Systems
sample appear equal.
8. frontale; pale median spot on frontal margin of head
capsule, mouthparts diagnostic, labrum distinct, mesosternum
pleura streaks, abdomen very wide medial dark stripe from 17, 8th large deletion of pigment median area, thin submedial
strips from tergite 1-8 then on the 9th an 10th, deeply
intruded into the 10th, spiracular spots, lateral projection
equal.
9. gildersleevei; mouthparts very diagnostic, labrum very
distinct, discontinuous submedial stripes on all tergites,
all tergites black transverse bands on posterial margins,
having spiracular spots, lateral projection equal in
length.
10.
heterotarsale; spot in front of median ocelli distinct
as per Traver like the shape of fleur-de-lis, mouthparts
diagnostic,
labrum
very
distinct,
abdomen
continuous
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submedial stripes bell shaped,
subanal plate very indentures.
lateral
projection
equal,
11.
interpunctatum Say; very pale all over especially the
male, prominent pale spot in front of median ocelli,
mouthparts diagnostic, labrum very distinct, pale legs with
faint banding, abdomen submedial and sublateral pale
predominant streaks, lateral projections equal.
12.
majus;
pale spot on frontal margin of head capsule,
mouthparts diagnostic, labrum very distinct, mesosternum
pleura streaks, abdomen very continuous submedial stripes,
having spiracular spots, with lateral projection equal.
13.
minnetonka;
pale spot on frontal margin of head
capsule, mouthparts diagnostic, labrum unknown, abdomen
with continuous stripes with spiracular spots, lateral
projections are unknown.
14.
pallidum; mouthparts are diagnostic, labrum unknown,
abdomen very faint pale submedial stripes unlike any in the
genus
continuous,
blackish
tergite
transverse
bands,
th
lateral projections 8 is shorter.
15.
proximum; pale pinkish stripe on the frontal margin of
head capsule, mouthparts diagnostic, labrum distinct,
mesosternum pleura streaks, abdomen with continuous pale
submedial stripes, lateral projections the 8th is noticeably
shorter.
16.
Ohioense dark type; very dark all over, mouthparts
diagnostic, labrum distinct, mesosternum pleura streaks,
abdomen with very discontinuous stripes all pale spots coma
shaped, spiracular spots, lateral projections sub-equal, 8th
slightly shorter.
17.
Ohioense light type; pale stripe frontal margin of head
capsule,
dark
cinnamon
color
all
over,
mouthparts
diagnostic, labrum distinct, mesosternum pleura streaks,
abdomen with very wide continuous stripes, spiracular
spots, lateral projections sub-equal, 8th slightly shorter.
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Some of the following descriptions are first descriptions for;
Conjunctum, majus, proximum, and ohioense
Full Larva Descriptions
affine
Traver 1933
This is the original description plus 1937 updates
To the best of our knowledge affine has never been reviewed since 1937
It took me 4 years to consider doing a complete illustration of the larva. But on behalf
of all that Dr Traver did for us and this genus, I felt we should try to represent her
thoughts from 1933, and see if what she said could be made into something we can all see
for the first time.
Body size; 7-8 ♂ mm;
Tails; 15 ♂ mm
Male description based on white mesosternum and size.
General appearance; Small slender nymph. Light brown in color,
the head particularly reddish. Abdomen dorsally
with 6
longitudinal stripes, Lateral projections equaled in size as in
interpunctatum Say.
Head capsule; bright red-brown. Anterior to median ocelli, a
large white mark shaped like a mayflies hypopharynx above.
Another large white mark lateral to each lateral ocellus.
Lateral margins pale yellowish, with narrow central brown band.
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Small light dot on each side of the frontal boarder. A median
and two lateral light spots on the occiput. Antennae pale brown.
Thorax; Wide pale mid-dorsal band the length of the thorax;
widest at the anterior margin of the pronotum. Pronotum white on
lateral margins except anterior angle, which is brown (similar
to sample). Remainder of pronotum brown except for three
parallel transverse white dashes on each side. Few small white
marks on mesonotum near wing roots. Ventrally whitish, with
transverse brown band across the mesosternum.
Legs; pale brown. Femora pale yellowish at each end, and with a
pale central band. Tibia white apically, and a white band near
basal end. Apical half of tarsus white.
Abdomen; (illustration is a reasonable facsimile) A wide white
longitudinal white band the length of the abdomen on each side
of the median dorsal streak. These bands somewhat irregular,
since the brown median streak is widest at the center of each
tergite. A narrow light line on each side close to the lateral
border, and between this and the central wide light bans,
another narrow light line. Lateral projection of the 8th and 9th
are about equal.
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3 pale stripes as per Traver
Ventrally; yellow, prominently bordered and marked with reddishbrown. Sternite 9 brown except semi-circle area on the posterior
margin at median line, and a narrow light area on each side like
illustration but with tan transverse band at each Sternite, and
the 9th being more brownish.
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Canadense
Walker 1853
Modern re-description to original form
Without synonyms
Notes; this description is based on; Clemens 1915, Traver (1935) couplets,
and many collected, reared, and dissected samples from the Bronte creek
watershed in southern Ontario. This form in the larva state does not have
another “type” regarding maculation. In the adults we see great variation,
see the adult section description showing 3 variations of abdominal
maculation. It is my suspicion and we suspect that the potential larva we
are holding under the temporary name of “eliquentum” is in fact a
geologically substrate variation. As in the ohioense the mouthparts are
metamorphically different. We will insert the larva illustration here
under canadense as we now feel this is where it should be until further
notice. We will also include pictures of the larva in the photo plate
section.
General
appearance;
medium
brown-yellow
with
continuous
submedial streaks, with lateral projections of the 8th and 9th
being equal in length.
Body size; 11 mm ♂, 13 mm ♀ ,
Tails; 22 ♂ 15-17 ♀mm
Head capsule; no pale spot on median frontal margin, large pale
lateral areas just lateral to the antenna bases, without black
spots, U shaped distinct purple line from antenna base to
antenna base, with a median crania spot, spot in front of median
ocelli kind of clover ♣ shaped spot, there are two small black
spots behind the lateral ocelli, sometime a reddish mid cranium
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spot at the palmen body, with a large pale area in the median
area to the posterior edge.
Mouthparts; head capsule if more square shaped than others but
not elliptical like candidum, and ohioense dark, on the crown of
the maxilla there are 10-11 pectinate setae combs, and 25-30
setae in the submedial row with 15-18 being fimbriated in
nature, on the mandibles there are 6 teeth on the inner side of
the outer canine, and commonly 0 on the inner side of the inner
canine,
all
other
mouthparts
besides
the
labrum
are
indistinguishable from others in the genus.
Labrum; moderate indenture on the frontal margin, median robust
setae set well back, 4 single setae followed by 2 rows of 3,
then 2 rows of 4, then 3 rows of 5, most dorsal setae forward of
robust setae.
Pronotum; principally pale yellow, hyaline yellow lateral
boarders, followed inward by long brownish-black streaks pale on
the median area kind of leaf shaped, large pale median area
broken up with fine brown lines sort of forming an X in the
middle often a small black median spot, lateral to the middle a
smaller black coms shaped spots that transcends into the adult
stage.
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Notum; very much like the pronotum mostly pale yellowish with
brown spots, in very mature samples the scutellum will be
black, the lateral boarders are very dark near black at the
forewing roots, pleura streak are present and often wrapping the
sternum.
Legs; not typically clearly marked as others, often a ruddy-tan
colored but not dark, fore femora with a median dark band
followed by a large pale spot, followed by a darker spots
terminating at the joint with a pale area. Middle femora often a
longitudinal median line bending to the posterior edge. Rear
femora pale line restricted to the posterial margin. All femora
have black spots that coincide with femoral bandings in the
adults.
Abdomen; having very wide pale continuous submedial stripes that
surround a very fine median brown line that deeply intrude into
the 10th, lateral boarders narrowly pale yellow on all tergites,
there are a series of pale spots almost forming a secondary
sublateral pale streak between the gills and the submedial
stripes, most samples with have black shading in the spiracle
areas (but not spot).
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Ventral view; This illustration is a female sample and they have
sublateral ventral brown stains from the 1st to the 9th, on the
male these marks are often from the 6th through the 9th, from the
7th through the 9th these spots form a blackish longitudinal bar
that often terminate in the 9th with black spots, posterior area
of 9th brown.
Canadense variation type; we will continue to study this
potential form that we are placing here as canadense, that we
have temporary named eliquentum. There is very little in common
in the larva maculation both dorsal and ventrally, but from a
mouthpart morphology stand point they are different but it is
way too close to canadense, and the adult female we have aligns
very well with canadense see female imago page over. The other
very distinct feature is there are commonly two complete
tracheas in the 7th gill which we have not seen in any forms in
this genus.
So for now until we know otherwise it is fair to hold eliquentum
as a geological substrate variation of canadense.
Canadense / eliquentum?
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One strange anomaly is the how the black line forms a ~ shape
around the spiracle folds; they are not spots but in fact true
black outlines of the spiracle area. Here is a picture of the
full larva and the adult female imago. This is not a one of, we
have 3 matching larva and the adult, and David Funk has a male
sample on Bold System that aligns with our female.
eliquentum sample 2
eliquentum sample
We will be doing a full rearing study of this variation to see
what it potentially is. With both the larva and adult both
having strange black outlined spiracle lines more investigation
is need, but for now it works within the true canadense form.
The name eliquentum was chosen to represent the very eloquent
black markings.
candidum
Traver 1935
Notes; Spieth 1947 unjustifiably synonymized candidum to
complex then made it a subspecies of interpunctatum Say.
reinstated candidum and it has remained a valid species
description is based on Traver 1935 couplets and larva table,
Lewis 1974 A, and reared samples from southern Ontario.
a frontale
Burks 1953
since. This
Burks 1953,
General appearance; blackish-brown with discontinues submedial
stripes 8th lateral projection is shorter than the 9th.
Body size; 7.5 ♂ mm, 9 ♀ mm.
Tail size; 18-20 ♂ mm, 15 ♀ mm.
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Truer head shape;
Head; candidum has a very distinct head shape it is very oval,
all head capsule illustrations where done on a genus friendly
template and were never intended to represent every form in the
genus by shape but rather by maculation. No pale spot on the
frontal margin but very dark brown almost black on the frontal
margin, 2 very small pale spots on either side of the antenna on
the forward lateral margin, small pale white to hyaline areas
from the compound eyes to the lateral margin, with big black
coma spots = (from compound eyes towards the lateral boarder,
spot in front of median ocelli historically very triangle ▼
shaped as noted by Burks and Lewis, in front of that is a black
midcrania black spot, each lateral ocelli have a black triangle
▼ shaped spot behind it.
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Mouthparts; Lewis 1974 indicates 7-8 pectinate setae combs on
the crown of the maxilla, our Ontario samples all had 7, there
are 15-25 setae in the submedial row with less than 10 being non
fimbriated, the mandibles commonly have 8 teeth on the left
inner side of the outer canine, and 5-6 on the right. The inner
side of the inner canines there are no teeth present. All other
mouthparts are indistinguishable from others except the labrum.
Labrum; without a doubt very distinct, having a single row of
ventral robust setae that is in a curved line and not coming
near the forward margin moderately indentured frontal margin.
Pronotum; lateral edges very pale white or hyaline, often a very
small blackish spot encapsulated in the forward lateral area,
moving inward with a large dark coma shaped streak, with a
submedial pale area, then a very large black coma that becomes
the black marks on the pronotum in the adult, with a large onion
shaped spot in the median area.
Notum; lateral areas black moving inward with large pale areas
that have dark marks inside, center of notum orangey-yellow in
the longitudinal suture, scutellum and post scutellum areas
black.
Legs; fore femora dark median band followed by a thin pale band,
with another wide black band terminating with a large pale area
at the joint, tibia and tarsi black banded. Middle femora as in
fore femora, hind a few pale spots mostly blackish. All femora
having back spots in the median and apical areas as in the
adults.
Pleura; unmarked but coxa and trochanters are spotted with
blackish-brown spots, middle and rear are striped.
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Abdomen; very distinct discontinuous submedial stripes and the
8th lateral projection is noticeable shorter that the 9th.
Submedial pale spots on tergite 1 large and round and are unable
to be seen in fully mature samples, see immature sample in photo
plate, all submedial spots create a vase shaped pattern from
tergite 2-9
as in gildersleevei, median line barely intruding
into the 10th tergite, lateral margins very dark often a
distinct yellow stripe on the spiracle folds, spiracular spots
present but small from 2-9 some adults may have a trace of a
spot on the 1st. Spot on the 9th is often very small and hard to
see as black shading is present, lateral areas of 9th and 10th
black.
Ventral; pale yellow to orange on females silvery-white
laterally for males, both male and female share the same ventral
marking patterns, the females do not extend their spots to the
1st or 2nd segment as many in the genus do. Ventral markings are
very distinct and consistent to form, having a black lateral
longitudinal line on the 7th, a larger black line on the 8th and
a distinct black U shaped mark that is widest at the anterior
area almost shaped like a “Blue Jay” bird wrapping around the
posterior area of the 9th and coming to a black spot, anteriorly
shaded with brown.
Tails; yellow-blackish-brown with articulations
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Carolina
Banks 1914
Notes; we have no S carolina in our area of southern Ontario they are only
eastern towards the Covey Hill PQ area. This description is based on
Traver 1935 larva table page 303, Burks 1953, Lewis 1974 A, samples at
Bold Systems Museum, and 3 samples sent to me from Ashville NC area for
dissection from Joshua Doby. Substrate does affect the adults and
therefore also affects the larva. We have seen several photos that are
golden yellow gray in color, but most samples are very pale gray to dark
gray.
General appearance; pale gray throughout with little in the way
of pale markings, Traver 1935 states lateral projection of the
8th is longer than the 9th. This character is not reliable in
immature samples. When full grown the character is creditable
but must be employed on samples at the 22nd to the 24th instars,
so the wing pad is reaching the back of the second segment, or
to the back of the 4th segment, being the 24th instars.
Body size; 10 ♂ mm, 12 ♀ mm.
Tails; 18-22 ♂ mm 15-17 ♀ mm.
Head; compound eyes are very wide spread in both male and
females; use the ventral side of the 9th sternite to look for
claspers, head is generally very brownish-gray reddish-purple
between the antenna bases and the frontal margin, no pale spots
on frontal margin, slim and defined pale lines from the compound
eyes to the lateral boarder, with small pale black smears that
become the small black spots at the corners of the compound eyes
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seen in the adults; [Pale spot in front of median ocelli],
although in use now as a key of sorts it must be noted that
these spots are variable in all forms in the genus. As a rule
they are a great tool to help sort larva to form. They are
variable in and near the molting phase. The interior head
capsule slowly pulls away from the soon to be exuvia. These
actions do alter the size and shape of the spots at times, for a
period of time. Usage should be employed in combination with
other characteristics of the form; Spot in front of median
ocelli is often T shaped without a midcrania spot. Most samples
will have very faint gray spots behind the lateral ocelli,
cranium suture most often pure cream colored.
Mouthparts; (Lewis 1974 A), 10 pectinate setae combs on the
crown of the maxilla, 20-30 setae in the submedial row, 7-8
teeth on the inner side of the outer canine, and 2 blunt teeth
on the inner side of the inner canine, all the other mouthparts
are indistinguishable from others in the genus other than the
labrum.
Labrum;
See Labrums blueprinted
Pronotum; variable hyaline lateral margin can be very large,
obscured sublateral black stripe, submedial pale are, a black
spot on either side submedial, median area orangey-gray-brown.
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Notum; variability is clearly seen in these two different
samples, this one does show a prominent median stripe; it should
be noted that the stripe is in fact the opening longitudinal
suture, with the pronotum suture, and cranium suture all in the
rupture state.
Legs; all femora with little in the way of pale markings, all
femora joints are pale, a slight pale median spot on each femora
but vey obscured.
Abdomen; (very distinct from all others except floridense both
species a very under maculated on the dorsal surface of the
entire abdomen, and may share similar geography). Illustration
based on Bold Systems sample HIEPT027-09 - Stenacron carolina
[COI-5P:407].
No continuous submedial stripes, rather short thin pale
submedial spots from tergites 2-9, some samples as illustrated,
the 3-4th may be enlarged, the 9th are typically fine points on
the anterior area of the 9th. Stripes deeply intrude in to the
10th. Lateral area hyaline to tan colored with pale stripes, no
spiracular spots; slightly forward of spiracle folds a small
pale spot aslant often covered by the gills.
Ventral; generally pale throughout, brownish lateral maculation
shading from sternite 6-10, some sample can be rather blackish
at the terminal lateral areas almost forming a line.
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hh
Tails; smoky with pale articulated areas, turning dark gray at
the end.
Conjunctum
Dark types
Traver 1935
First description
Notes; this description is based on many collected and reared samples that
keyed out as adults to this form described in the Biology of a Mayfly
Needham, Traver, and Hsu (1935). The larva exuvia of reared samples key to
larva of this form. There currently are two distinct geological variations
for this form. They are the same for the most part in the larva stage;
However in the dark variation the abdominal submedial stripes are
discontinuous. In the light type the stripes are continuous.
General appearance; Blackish brown throughout with
discontinuous dorsal median stripes. 8th and 9th
projections about equal in length.
Body size; 8-9 ♂ mm 10-11 ♀ mm
Tails; 18-22 ♂ mm
partial
lateral
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Head capsule; oval in shape and depressed as in other forms and
species in the genus. Typically having many black marks. No pale
spot on the median frontal margin as in (frontale) and other
forms. Pale spot in front on median ocelli often ♥ shaped. Black
spot in front of this spot as to coincide with a midcrania spot
seen in the adult stages. Small pale spots present below and
lateral to the antenna bases on the anterior margin. These spots
often surrounded by two small black spots. Triangular pale spots
on either side of the lateral ocelli, these spots extent to the
lateral margin as in all forms in the genus in the general shape
of a stripe. Black markings in front of the compound eyes streak
like in shape that almost connects with the spots in front of
antenna bases. There are two black spots on the vertex behind
and close to the lateral ocelli. Often a red spot in between
these black spots where the pulmonary body is located. Posterior
edge of head capsule dark brownish-black.
Mouthparts; on the crown of the maxilla there are most often 10
heavy pectinate setae combs on the left and 11 on the right.
Submedial row of setae has 30-37 setae in it and typically 29 of
them are fimbriated in nature. The mandibles have 6 teeth on the
interior side of the outer canine on both the left and right
side. Regarding the inner canine, in most samples there is 1
tooth on the left and 2 teeth on the right on the inside. All
other
mouth
parts
coincide
with
and
are
reasonably
indistinguishable from all other species and forms in the genus
except the labrum.
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Labrum; both the light and dark type labrums are almost
identical. There is a single row of 4, then a row of 2, then 5
rows of 3 robust setae, and the dorsal side fine hairs are
forward of the ventral robust setae.
Pronotum; similar to others in the group by having pale lateral
edges and a crescent shaped pale spot in the submedial region.
The remaining areas blackish-brown. Often having small black
marks in the anterior submedial area that coincides with
pronotum makings in the adult stages.
Mesonotum; Blackish-brown with small pale areas often having
black lateral edges. Wing pads dark blackish with greenishyellow hue from the fully formed adult wings encapsulated.
Mesosternum; Pale yellow, pleura marks are present
lateral edges in front of the mid and rear legs.
at
the
Forelegs; There is commonly a black spot on the forecoxa. The
femora in general having the appearance of banding. There is a
darker longitude band in the median area, laterally followed by
a light band and then a very dark band at the terminal end.
Often a large black area at the joint on the dorsal side. Tibia
basil area very dark at the joint, followed by a pale area,
another dark area and terminating at the tarsi joint as pale
yellow-whitish. Tarsi marked as in tibia, fore claws not
denticulate.
Middle leg; Coxa heavily marked in black, median longitudinal
stripe restricted to the posterior edge followed by a pale
stripe that is broken. Apex of femora very dark. Tibia marked as
if fore tibia.
Rear leg; Coxa slight black spots. Femora almost entirely
blackish. Pale median spots with a pale apex edge that has dark
spots. The posterior edge often having large blackish spots that
are restricted to the posterior edge.
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Abdomen dorsum male dark type; Lateral projections on the 8th &
9th are equal in length. Dorsally having discontinuous submedial
pale streaks. The general color is a dark umber tone with black
overtone hues. Submedial streaks on the 1st to the 6th tergite
are incomplete and do not connect to the anterior or posterior
edges of each segment as in, S carolina, S gildersleevei, S
candidum and S floridense. However on some samples these stripes
can connect to the posterior edge of the 6th tergite. From the
7th through the 9th tergite the stripes are continuous and the
median area of the 9th tergum has a ♦ diamond-ish shaped spot as
noted by Traver. Submedial streaks in the 10th tergite often
barely intrude into anterior of the 10th as mere faint yellow
arrows. In the male these streaks are most often yellow. There
are pale sublateral spots or streaks present from the 1st
tergite through to the 6th and often a very small pale spot near
the posterior-sublateral region on the 7th. These spots can all
be partially concealed by gills 1-6. Inside and posterial to the
sublateral pale spots is where the black spiracular spots are
located. These spots are often small and defused. In the male
larva they are more prominent and are from tergum 2 through the
9th. In the female they are most often incomplete being
difficult to see and are typically from the 3rd to the 8th. Gills
are purple-gray in color and oval in general shape terminating
in a point with internal branched trachea and with external
fibril trachea. The seventh gill is fingerlike in shape with one
trachea present with a few very fine setae hairs at the terminal
end.
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Abdomen dorsum female dark type; Lateral projection on the 8th &
9th are equal in length. Dorsally having discontinuous submedial
pale streaks throughout. The general color is a dark umber tone
with black overtone hues most often darker than the male.
Submedial streaks on the 1st to the 9th all discontinuous. In
most samples not touching ether the anterior or posterior edges
of the segments. Thus looking very much like the illustration by
Dr V K Mayo in the Biology of a Mayfly 1935 (fig) 92 page 315
for S gildersleevei.
The median line is wide and continuous from the 1st through the
9th. Each one slightly lens shape thus; (). The female can be
very difficult to separate from S gildersleevei. Having short
wide coma shapes surrounding the wide medial line. All posterior
edges of tergite very dark with transverse shading that can be
almost black like in S gildersleevei and S pallidum. The
spiracular spots are larger and more intense than the male but
are blended into dark background that transfers into the adult
stages.
The 9th tergite the stripes are discontinuous and in the median
area of the 9th tergite has a ♦ diamond-ish shaped spot as noted
by Traver. Submedial streaks in the 10th tergite often barely
intrude into anterior of the 10th as mere faint yellow arrows.
In female samples these discontinuous stripes will appear orange
in color as the eggs are present in the abdominal cavity. The
sublateral marks from the 1st through 6th like the male. The
subanal plate in both the female and male are squareish and has
no indenture on the apex of posterior edge.
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Abdomen sternum; Female orange in color, male yellow pale
whitish in general color. The female has sublateral cinnamon
colored longitude maculation stains from the 1st or 2nd segment
to the 9th. From the 5th to the 9th often dark brownish and
highlighted with black on the 8th and 9th. On the male these
marks are darker and are present from the 6th through the 9th.
On the posterior edge of the 9th the sublateral streaks wrap
around the posterior edge to form a crescent shape facing
posteriorly. There is often an indentured stain in the median
area of the crescent shaped stain on the 9th facing anteriorly.
Posterior edge of the 9th and 10th blackish. Ganglionic median
stains from the 1st to the 8th are often visible in the female.
Sometimes looking very much like the shape of a boat anchor
facing anteriorly.
Tails; Blackish brown with pale articulations.
Conjunctum
Light types
Traver 1935
First description
Notes; this description is based on many collected and reared samples that
keyed out as adults to this form described in the Biology of a Mayfly
Needham, Traver, and Hsu (1935). The larva exuvia of reared samples key to
larva of this form. There currently are two distinct geological variations
for this form. They are the same for the most part in the larva stage;
However in the dark variation the abdominal submedial stripes a
discontinuous. In the light type the stripes are continuous.
General
appearance;
dark
cinnamon
brown
throughout
with
th
th
continuous dorsal median stripes. 8 and 9 lateral projections
about equal in length.
Body size; 8-9 ♂ mm, 10-11 ♀ mm
Tails; 20 mm
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Head capsule; dark cinnamon brown without a pale spot on frontal
margin as in frontale. In many samples the entire frontal margin
can have a very faint pale edge. Black-purple line from antenna
base to antenna base in a U shape like a smile. Lateral to
antenna on the forward margin 2 black spots preside with a pale
spot in between. In front of each compound eye is a black streak
that is like a smear heading towards the lateral edge. Spot in
front of median ocelli is often ♥ shape with extensions as per
illustration above with a midcrania spot forward of that. There
are often very fine black lines at the cranium Suture, and black
spots on the vertex behind the lateral ocelli.
Mouthparts; on the crown of the maxilla there are most often 10
heavy pectinate setae combs on the left and 11 on the right.
Submedial row of setae has 30-37 setae in it and typically 29 of
them are fimbriated in nature. The mandibles have 6 teeth on the
interior side of the outer canine on both the left and right
side. Regarding the inner canine, in most samples there is 1
tooth on the left and 2 teeth on the right on the inside. All
other
mouth
parts
coincide
with
and
are
reasonably
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indistinguishable from all other species and forms in the genus
except the labrum.
Labrum; both the light and dark type labrums are almost
identical. There is a single row of 4, then a row of 2, then 5
rows of 3 robust setae, and the dorsal side fine hairs are
forward of the robust setae.
Pronotum; similar to others in the group by having pale lateral
edges and a crescent shaped pale spot in the submedial region.
The remaining areas blackish-brown. Often having small black
marks in the anterior submedial area that coincides with
pronotum makings in the adult stages.
Mesonotum; Blackish-brown with small pale areas often having
black lateral edges. Wing pads dark blackish with greenishyellow hue from the fully formed adult wings encapsulated.
Mesosternum; Pale yellow, pleura marks are present
lateral edges in front of the mid and rear legs.
at
the
Forelegs; There is commonly a faint black spot on the forecoxa.
The femora in general having the appearance of banding. There is
a darker longitude band in the median area, laterally followed
by a light band and then a very dark band at the terminal end.
Often a large black area at the joint on the dorsal side. Tibia
basil area very dark at the joint, followed by a pale area,
another dark area and terminating at the tarsi joint as pale
yellow-whitish. Tarsi marked as in tibia, fore claws not
denticulate.
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Middle leg; Coxa moderately marked in black, median longitudinal
stripe restricted to the posterior edge followed by a pale
stripe that is broken. Apex of femora very dark. Tibia marked as
if fore tibia.
Rear leg; Femora almost entirely deep brownish. Pale median
spots with a pale apex edge that has dark spots. The posterior
edge often having large blackish spots that are restricted to
the posterior edge.
Abdomen dorsum male light type;
Median line on tergites 1-3 fine and incomplete, 4-7 very
irregular but forming a complete line for the most part. 8th
often like majus and frontale having a median line that does not
reach it posterior edge, 9th distinct ♦ diamond-ish shaped
median spot as per Traver 1935, 10th with median spot. Submedial
streaks are continuous and slightly intrude into the 10th.
There are a series of small pale spots from 1-7 near the gills
but not covered by the gills 1-6. The terminal lateral edges of
segments 1-7 are pale with very fine small pronounced spiracular
spots.
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Abdomen sternum; Female orange in color, male yellow pale
whitish in general color. The female has sublateral cinnamon
colored longitude maculation stains from the 1st or 2nd segment
to the 9th. From the 5th to the 9th often dark brownish and
highlighted with black on the 8th and 9th. On the male these
marks are darker and are present from the 6th through the 9th.
On the posterior edge of the 9th the sublateral streaks wrap
around the posterior edge to form a crescent shape facing
posteriorly. There is often an indentured stain in the median
area of the crescent shaped stain on the 9tthfacing anteriorly.
Posterior edge of the 9th and 10th blackish. Ganglionic median
stains from the 1st to the 8th are often visible in the female.
Sometimes looking very much like the shape of a boat anchor
facing anteriorly.
Tails; brown with pale articulations.
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frontale
Banks 1910
Re-described without synonymous forms
Notes; this description is based on; Banks (1910), Traver (1935) couplets,
Spieth 1947, Burks (1953), and many collected, dissected, and reared
samples from the Bronte creek watershed in southern Ontario.
General
appearance;
medium
brown-yellow
with
continuous
submedial streaks, with lateral projections of the 8th and 9th
being equal in length. Most samples have a pigment deletion in
the median stripe on the 8th tergite.
Body size; 8 ♂ mm, 10-11 ♀ mm.
Tails; 18-22 ♂ mm 15-17 ♀ mm
Head capsule; ovate in shape and depressively flattened, shaped
not as in ohioense, candidum, or proximum, but like all others
in the genus. Typical samples will have a pale cream or pinkish
spot on the median anterior edge or frontal margin. Heavy
shading around the antenna bases and extending to the midcrania
area, 1 small pale spot and 1 small dark spots under and lateral
to the antenna bases, followed by a large lateral pale area from
the compound eye to lateral edge as in all others in the genus.
Black tear shaped black spot in front of compound eyes pointing
to the median area. Pale spot in front of median ocelli commonly
in the shape of a ♥ see below with a dark spot in front as to
coincide with midcrania spot in the adults. There is commonly a
purple-brown spot at the cranium suture and palmen body, with
large black distinct spots on vertex often encapsulating the
posterior areas of the lateral ocelli. Posterior edge shaded
dark brown.
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Mouthparts; on the crown of the maxilla there are normally 8-9
pectinate setae combs, 9L and 8R. In the submedial row of setae
there are between 39-46 setae with 10-14 on each being none
fimbriated in nature. On the mandibles there 6-7 teeth on the
inner side of the outer canine with 0-2 teeth on the inner side
of the inner canine, all other mouth parts coincide with others
is the genus and are indistinguishable except for the labrum, we
were able to blueprint this form.
Labrum; very small forward indenture on anterior margin. Single
row of 5, then 6 rows of 2, robust setae on the ventral side
coming to the frontal edge. All fine dorsal setae are behind the
robust setae.
Pronotum; Like others in the genus by having pale lateral edges
followed inward by a blackish-gray (leaf) like coma type mark,
with a fine pale stripe, followed by a large blackish spot as to
coincide with pronotum oblique sublateral spots in the adult,
with a large anterior-medial pale spot.
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Pronotum
Mesonotum; very much like pronotum having small pale spots and
dark lateral boarders. Wing pads typically reddish-brown with
slight greenish hue in the female.
Forelegs; Femora banded with a median brownish band, followed by
a pale yellow band, a pale area at the joint. Typical samples
will normally have small black spots, one in the anterior-medial
area, and two near the femora joint. Tibia dark brown at the
apex followed by a pale band another larger dark band, and
terminating at the tarsal joint with pale yellow. Tarsi same as
tibia, fore claws not denticulate. Middle and rear legs
following the same pattern but the dark areas are larger.
Abdomen; Lateral projections of the 8th and 9th segments are
equal in length, brownish yellow in general coloring, with a
wide median brown stripe that typically has a pigment deletion
in the 8th tergite. This deletion can encapsulate all of the 8th
part of the 7th, and also part of the 9th. Having narrow
submedial pale stripes that are continuous from the 1-10 and
expanding in width on the 8th due to medial stripe pigment
deletion. These submedial stripes commonly deeply intrude into
the 10th segment. The extreme lateral edges from 2-9 are dark
with large pale areas followed by a very dark sublateral area
where the spiracular spots are located, followed inward by a row
of pale spots.
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Sternum; Both the male and female have venter-lateral brown coma
shaped spots. On the female they are normally from the 1-9 like
above and on the males from the 6-9. The females are normally
yellow-orange in ground color due to eggs present in the
abdominal cavity. Males are typically whitish-yellow. Females
will likely have small medial brownish spots from the 4th to the
8th. Both having the posterior margin of the 9th shaded in light
brown staining. All of the 10th is normally darker brown
sometimes blackish.
Tails; medium brownish with lighter articulations
floridense
Lewis 1974
Based on his 1974 A&B descriptions
Notes: Reading both Lewis 1974 A, B, descriptions which appear to be the
same description, it is clear that size is a issue. He has larva size 8-10
mm, and male imago 7-9 mm? We can rule out confusion with interpunctatum
as floridense has 1-4 curved stout dorsal axial spines and no others in
the genus has axial spines. We can rule out larva confusion as floridense
tergite maculation is very distinct. The base line would likely be 8 mm
for the male, 10 mm for the female. It is unfortunate that the samples at
Bold Systems Museum larva photographed by Jeff Webb can’t be used to clear
this up. They are only in and around the 15-18 instars and are not full
grown. From our studies and Ide 1935 Stenacron larva reach full body
length at the 22nd instars when the wingpad reaches the posterior edge of
the 2nd tergite, then the wingpad rapidly grows till it almost reach’s the
posterior edge of the 4th tergite by the 24th instars. We have also
consulted The Mayflies of Florida and size is not covered.
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Body size; ♂ 8 mm, ♀ 10 mm.
Tails; unknown likely ♂ 18 mm, ♀ 15 mm.
The only samples to work from for illustration are the 3 samples
at Bold System that Jeff Webb photographed that are in the adult
photo plate section. With the lack of details in Lewis’s
descriptions our illustration are based on the bold samples.
Therefore head, pronotum and median ocelli spot illustrations
were not done. We were unable to handle any larva so the labrum
is also not blueprinted.
Head; shaped and marked as others in the genus, often a pale
spot on the frontal margin, maxilla with 8 or 9 heavy setae
combs on the crown of the maxilla with 20-25 setae in the
submedial row, mandibles with 7 teeth on the inner side of the
outer canine and 0 on the inner side of the inner canine.
Pronotum; mostly brown with hyaline lateral edges.
Notum; median are with large pale spots, scutellum light yellow.
Legs; brown and whitish-yellow bandings.
Abdomen; mostly brownish-gray, lateral projections are unknown
but likely equal in size. Lateral edges are pale, tergite 1 pale
median spot with transverse pale line, with a series of pale
sublateral spots from 2-7 as all in the genus, submedial pale
spots on tergites 1-7 very small often hard to distinguish,
large medial submedial “V” spot, 9th median brown
tergite 8th
spot breaking up median pale “V” spot. 10th tergite with pale
anterior areas barely entering the 10th segment. Expect
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variation in the size of submedial spots from 2-7 based on the
color of the substrate.
Ventral; pale yellowish females having pale brown ventrallateral spots becoming lines from the 7-9th on males from 7-9th
Gildersleevei
Traver 1935
Notes; this description is based on Traver 1935, Burks 1953, Lewis 1974 a,
and reared larva found in Bronte creek in southern Ontario in 2014. In the
photo plate are the first publically seen photos of a female gildersleevei
and a short video under the microscope was filmed. The only other known
photo is Lewis 1974a figure 16 which is horrible but for the day wasn’t to
bad.
General appearance; pale cinnamon brown with very discontinuous
submedial abdominal stripe, with equal lateral projection 8-9.
Body size; 10-11 ♂ mm, 13-14 ♀ mm
Tails; 24-26 ♂ mm, 18-22 ♀ mm
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Head; median frontal area pale without a pale spot some samples
having a small pale area lateral to each antenna base on the
frontal margin, large pale areas from compound eye to lateral
edge turning gray both forward and backward, generally a purple
strip from antenna base to antenna base anterior to antennas to
for a smile of sorts, typical samples with prominent median
crania spot in front of elongated pale triangle ▼ shaped spot in
front of median ocelli. Cranium suture pale white with prominent
purple spot between and behind the lateral ocelli being the
palmen body and trachea extension trunks. Very wide orange red
stripe from mid-vertex to scutellum, with black spots behind the
lateral ocelli.
Mouthparts; maxilla are highly diagnostic 11-13 pectinate setae
combs on the crown of the maxilla, all samples from Bronte Ck
all had 13, there are 30-45 setae in the submedial row, and our
Bronte samples averaged 36, on the mandibles there are 7-9 teeth
on the inner side of the outer canine, and 3-7 on the inner side
of the inner canine, all other mouthparts generally are
indistinguishable from all others in the genus except the
labrum.
Labrum; very shallow indenture on the frontal margin, median
robust setae .9 – 1.2/100th of a mm at 100X from the frontal
margin forming a single row of 6 robust setae, followed by 4
rows of 2. Dorsal fine setae is placed right on top of ventral
robust setae, there is one strange anomaly we only saw on
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gildersleevei labrums, there are 4 very long specifically placed
setae on the dorsal side they are almost robust in size they are
marked below we refer to them as coarse setae that are more than
double the length of standard setae.
4 Coarse setae
Pronotum; large pale yellow-hyaline lateral edges, followed
inward by a blackish-brown stripe, then by a pale brown leaf
shaped spot, a larger pale yellow are, 2 large submedial black
spots that transcend into adulthood, prominent orange-red medial
stripe.
Notum; mostly brownish with pale spots and larger pale orange
medial stripe scutellum is blackish-brown dividing the notum
from the abdomen.
Legs; well banded with brown and pale transverse stripes.
Abdomen; submedial pale stripe are discontinuous throughout
often vase shaped. Lateral projection of the 8th and 9th are
equal in length, medial stripe is a series of brown spot forming
a moderately complete line from 1-10, sublateral pale areas from
1-7 decreasing in size from 1 through 7 these spots are often
not evident due to gills and wing pads, they are easily seen
samples younger than the 22 instars. All posterior edges with
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transverse black bands, spiracular spots present on tergites 19, lateral areas of 7-10 blackish.
Ventral; pale yellow orange for females, whitish for males, at
the lateral margins of 1-6 silvery white, both male and female
only have ventral-lateral brownish-black lines from the 7th to
the posterior area of the 9th, wrapping around the posterior
area.
Tails; yellow-brown basely turning yellow-tan with very fine
brown articulations.
Heterotarsale
McDunnough 1933
First pure description
Spieth 1947; larva undescribed SYN, Burks 1953 contains synonym forms.
Notes; based on descriptions, reared adults and Traver 1935. Heterotarsale
adults only have tiny spots near the compound eyes on the frontal margin,
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and small blackish spots on the vertex and no other marking throughout the
body in the adult stages. This description is pure to form.
General appearance; Cinnamon ruddy brownish, with continuous
submedial dorsal stripes, lateral projections on the 8th & 9th
are equal in length and somewhat squareish.
Body; 9 ♂ mm, 11 ♀ mm.
Tails; 18-24 ♂ mm, 15-17 ♀ mm.
Head capsule; oval in shape and depressed as in other forms and
species in the genus. Typically having few black marks. No pale
spot on the median frontal margin as in (frontale) and other
forms, with rather large pale areas in front & lateral of the
antenna base. Pale spot in front on median ocelli often shaped
as mentioned by Traver 1935 as being in the shape of (fleur-delis). Very large pale areas on either side of the lateral
ocelli, this spots extending to the lateral margin along the
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cranium suture, and extending around the head capsule to the
posterior area. There are very small black spots touching the
anterior edge of the compound eyes. Lateral ocelli wide spread
with very fine pale black spot right behind them.
Mouthparts; there are commonly 9 pectinate setae combs on the
crown of the maxilla, and 30-35 setae in the submedial row, with
24-26 of them being fimbriated in nature. The mandibles have 5-7
teeth on the inner side of the outer canine and 3-4 on the inner
sided of the inner canine, all the other mouthparts are
indistinguishable from all others in the genus. We were able to
blueprint the labrum and it is distinct.
Labrum; Has a transverse median based row of spine setae just
back from the anterior edge with the entire anterior edge
without setae in front of this row, remaining areas sparsely
covered in setae. All other mouthparts match others in the genus
and are reasonably indistinguishable from each other.
Pronotum;
much
paler
than
others
but
similar
to
true
interpunctatum
(Say)
the
remaining
notum
pale
yellowish
background mottled with cinnamon spots. Wing pads are light
brown with yellowish adult wing color coming through.
Legs; are marked as others in the genus. Fore femora mostly pale
cinnamon and yellow with median and apical banding. Middle and
hind leg similar to fore legs, however more brownish than pale
yellow throughout.
Abdomen; 8th and 9th lateral projections are equal in size, and
short in overall length, with the 9th having the shape of a
bowie knife. The median line is light cinnamon with each section
of each segment, being arrow shaped with the widest end on the
anterior edge and the pointed end to the posterior edge, and
intruding deeply into the 10th tergite, with 10th posterior edge
being yellowish. Submedial streaks are continuous and uniformed
with a moderate width as they travel from 1st to the 10th. These
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streaks appear wider on the 6-9 as the median line diminishes.
There are a series of small pale sublateral spots from the 1st
to the 7th with a small pale spot in the anterior of the 8th
tergite, lateral to these spots is a darker area followed
outward by another series of pale spots, with the terminal
lateral edges being cinnamon in color.
Sternum; in the female the ground color is entirely orange, and
the males are whitish-yellow with bases of the gills being
hyaline. There are venter-lateral tan colored coma shaped marks
from the 6th through the 9th in the female. In the male these
marks commonly from the 8-9th. The 9th segment having a
transverse band rapping the lateral and posterior edge, with an
indentured median area shape like the tip of a finial. Subanal
plate is indentured in both the female and male.
Tails; yellowish-orange with fine brownish articulations.
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True interpunctatum Say 1839
Thomas Say
This is a synonym free description
Notes; Clemens 1924 clearly indicated the following. “The nymph is fully
described (as species number 3) by Needham 1905”. While we agree, there
are aspects of that description that cause confusion. Dr Needham was using
current wording that is now obsolete. It is also difficult to follow as it
appears as though he is jumping from the head to the abdomen and back to
the notum. We translated it to newer words and are utilizing that
information. This is very much based on 4 reared males and 9 reared
females from southern Ontario, as well as all comments from all previous
authors 1839-2010. It is my pleasure to bring a modern and very clear
description of Thomas Says original Stenacron interpunctatum.
General appearance; pale overall very small, with little
markings on the legs, submedial and sublateral dorsal stripes
continuous, 8th and 9th lateral projection equal.
Body size; 7.5 ♂ mm, 9 ♀ mm
Tails; 18-26 ♀ ♂ mm, Hagen 1861
Hagen 1861, 8 ♂ mm
Head; very pale overall with a brownish-tan-gray coloring, no
pale spot on the frontal margin, large pale areas from the
anterior of the compound eyes to lateral boarder wrapping around
to the frontal margin somewhat, a small black dot in front
compound eyes as in the adults, spot in front to median ocelli
large and almost connecting to lateral pale areas near lateral
ocelli, shape of this spot very much like a ♣ clover, there is
sometimes a midcrania spot present, vertex has a small black
spot on either side behind the lateral ocelli, remainder of head
pale brownish.
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Mouthparts; 9-10 pectinate setae combs on the crown of the
maxilla, 25 or less setae in the submedial row, our sample
indicated 20-23 as a average, with 7-9 being non fimbriated in
nature, mandibles there are 7 teeth on the inner side of the
outer canine, and 4 teeth on the inner side of the inner canine,
all other mouthparts are indistinguishable from others in the
genus except that labrum.
Labrum; shallow indenture on the forward margin, median robust
setae set well back commonly 2.0/100th mm 200 X, there is a
single row of 5 followed by 9 rows of 2 robust setae coming to
the forward lateral margin.
Pronotum; like the head very pale, large hyaline lateral edges
followed inward by a narrow dark S shaped line, then by a pale
brown spots shape like a Oak leaf, very large pale submedial
areas with fine brown lines, very dark at the anterior margin
becoming spots on the pronotum in the adults, median area
yellowish.
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Notum; primarily yellow for male orangey for females, with
longitudinal submedial and sublateral darker streaks, lateral
boarder often blackish.
Legs; fore legs smoky hyaline background, with a fine median
pale band followed by another darker area, with a yellowishwhite spot at the femora joint, on the median anterior area of
femora a purplish spot, and one at the femora joint. Middle leg
mostly pale smoky gray with longer pale spots. Rear legs all
gray
with
longitudinal
posterial
pale
spot.
All
true
interpunctatum Say we handled all had 1 long single paddle
setae, without a group of small setae near it in the medianapical-dorsal area near the femora joint on the rear femora.
Abdomen; distinctly striped, the median line is thin and
slightly darker than the other brownish areas, and deeply
intrudes into the 10th tergite, wide continuous pale submedial
stripes that also deeply intrude into the 10th, sublateral pale
spots are near connected from 1-7 and just entering the 8th in
the anterior area, these lines are not obscured by the gills,
but are by the fully grown wing pads, lateral margins pale
hyaline with small brown longitudinal stripes on the spiracle
ducts, no spiracular spots, very little dark shading, entire
lateral areas of the 7-10th slightly darker brown, females are
yellow-orange do to eggs in the cavity.
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Ventral; very pale yellow-white for males orangey yellow for
females, on the males all the areas near the gills is silverywhite, on both male and female they tend to have very tiny brown
stains sublateral to the edge from 3-6, sometimes absent,
blackish-brown longitudinal-lateral lines from the middle of the
7th to the posterior end of the 9th with a small black spots at
each side of the subanal plate. Our studies concur with Ide 1935
the male genitals can be examined earlier than the last instars;
the earliest sample we could examine was about the 22nd instars.
The genitals are somewhat fully formed. However the spines are
present as is the lobes but the lobe shape is hard to define;
the penis is in a protective sheath and not yet full size. We
used this to try to predetermine species concept when rearing
what was looking to be a new species.
Tails; yellowish slight orange cast with pale articulations.
Reared male samples interpunctatum Say from Bronte Creek
southern Ontario from moderate color density substrate.
in
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Majus
Traver 1935
First description
Notes; this species was created from Traver 1935 couplets, and larva table
page 303 The Biology of a Mayfly. Her description of the adults allowed us
to key reared adults to the historical profile 1935. The larvae were
retraced using reared exuvia to ensure accuracy. This for majus is very
district by it very large prominent spiracular spots especially on
females. There are two different geological variations of this larva.
However variation is little but we will comment when the information is
usable.
Body size; 9.5-10.5 ♂ mm, 11-12 ♀ mm
Tail size; 18-22 ♂ mm, 18 ♀ mm
General appearance; pale cinnamon brown with prominent odd
continuous submedial abdominal stripes, with a diamond ♦ shaped
spot in the median area of the 9th tergite as per Traver 1935
lateral projection of 8th and 9th equal.
Head capsule; Deep brown in the frontal median area with a pale
spot or stripe on the frontale margin, a moderate sized pale
spot forward and lateral to each antenna base on the frontal
margin, purple-black line from antenna base to antenna base like
a faint smile, with a median crania spot in front of a median
ocelli pale spot sort of a T and ▼ triangle shape combined,
moderate pale areas lateral to compound eyes turning gray I to
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the posterior margin, a black spot behind each lateral ocelli,
vertex orangey in the median area.
Mouthparts; on most samples there are 9 pectinate setae combs on
the left maxilla and 10 on the right, and in the submedial row
there are 34-35, rarely more rarely less. On the mandibles there
are 6 teeth left and 7 teeth on the right inside of outer
canine, and 0 on the inner side of the inner canine. All other
mouthparts are indistinguishable from all others in the genus
except the labrum.
Labrum; we slide mounted 5 labrum and all had this anomaly that
is not on other forms, 3 were from exuvia, and 2 were from full
larva, we cannot conclude for sure but all samples had a median
like elliptical ridge see arrows indicating this. At first we
thought it was a fold in the exoskeleton but the problem is the
robust setae follow it with consistence.
The lateral spread from point to point is also short making the
robust setae and ridge sort of “U” shaped but the frontal
indenture is very shallow average sample .5/100th of a mm at
200X. There is a single row of 9 robust setae becoming twice the
length of the median one at the frontal margin. The other
interesting thing only seen on gildersleevei is the very long
dorsal setae see below.
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Lateral spread
Ridge/fold
Long setae
Pronotum; fine pale lateral area large in the forward area,
followed inward by a large brownish-black leaf shape stripe,
large pale submedial areas with black stripe to represent black
lines in the adults, median area mostly orangey-brown.
Notum; mostly brown with pale spots and medial orange stripe.
Leg; very well banded rear femora brownish all with black spots
especial at the femora joints.
Abdomen; incomplete medial brown stripe from 1-10. This stripe
is typically a series of fine lens shaped spots thus (), in some
sample not connecting to either the anterior or posterior edge
of each tergite, that is a rule often broken. The submedial pale
stripes are continuous from 1-10 but often uniquely expand on
the posterior margins of tergites 4,7, and 9. This form can very
much be confused with frontale as it also commonly has a
deletion of pigment in the median line tergite 7 and 8, however
distinction from frontale is the width of the median line it is
very wide on frontale, and very thin here.
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Ventral; brown ventral-lateral spots from 6-7, these spots
turning into comma shaped and becoming a “U” shape as it wraps
the posterior margin with a brown transverse line in the median
area.
Tails; dark brown-yellow with fine brown articulations.
Minnetonka
Daggy 1945
Notes; Lewis 1974 the Taxonomy and Ecology of Stenonema Mayflies
description of the larva is so vague we could not make a full
dorsal illustration but we wanted to. Because of what
information is there it is likely very close to canadense. So
for the opening full larva below the illustration is a canadense
with a median frontal spot added to it. Making a very reasonable
facsimile of the abdomen was not as hard, it was reversed
engineered. We took the adult description combined it with our
knowledge of transcending maculation in the genus specifically
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the
valid
species,
and
were
able
to
offer
a
likely
representation. Description is basically Lewis 1974 combined
with my genus knowledge and the complete adult morphology. My
additional comments in parenthesis.
Body size; 9-10 ♂ mm, 11♀ mm.
Tail size; unknown
Head capsule; anterior to compound eyes uniformly brown,( will
have pale dark marks at antenna bases that will coincide with
lines on the clypeus of the adults, there will be a midcrania
spot in front of pale spot that is in front of median
ocelli).(there will also be a small black spots in front of the
compound eyes and behind the lateral ocelli).
Mouthparts; there are 9-10 pectinate setae combs on the crown of
maxilla, and 30-40 setae in the submedial row. Mandibles there
are 6-7 teeth on the inner side of the outer canine, and 3-4
blunt teeth on the inner side of the inner canine. All other
mouthparts are indistinguishable from all others in the genus.
We did not hand minnetonka larva so we cannot comment on labrum
but likely very distinct.
Pronotum; brown with a few pale areas, (would have hyaline
lateral edges, and submedial black spots that coincide adult
stage).
Notum; (likely darker brown with pale areas and likely a pale
median longitudinal suture, and blackish lateral margins along
wing bases).
Legs; alternating brown and white bands (with black spots near
the femora joint as in the adults).
Abdomen; having a pair of continuous
10, widest and the 8th and 9th tergite
10th, (would have reducing sublateral
to coincide with very pale sublateral
spiracular spots present from tergites
submedial stripes from 1barely intruding into the
areas under the gills as
areas of the adults, with
1-9).
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Ventral; variable brown lateral spots from 4-9
Tails; light brown-yellow basil half alternating dark light band
apical half.
Ohioense
Traver 1935
First description
Light types
Notes; in my 2014 rearing study of this form, the larva clearly indicate
two separate types of larva that will rear out as adult ohioense. The two
types are subject to specific substrates only. We are referring to these
two types as light type and dark type. Both of these types possess subequal lateral spines on the 8th and 9th segment of the larva abdominal
cavity. Because the light form aligns with Travers table and couplets in
the Biology of a Mayfly, the lighter form should be considered the
standard and the dark type the variant.
Lateral projection measurements 100X;
8th lateral projection average length; 7/100 mm
9th lateral projection average length; 11/100 mm
Female larva; 13 mm
Male larva;
9 mm
Tails;
Tails;
17 mm
15 mm
Light form;
General appearance moderate brownish throughout with continuous
submedial stripes.
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Head capsule; in both the male and female the head capsule is
highly depressed and oval in shape as in others in the genus,
pale stripe frontal margin, pale spots in front of and lateral
to the antenna bases, ♥ shaped pale spot in front of the median
ocelli. Antenna bases heavily shaded in black, other than the
extending pale stripe from the compound eyes to lateral edges.
Very large black comas thus = ( in front of each compound eye as
in candidum but extending further than antenna bases and close
to lateral edges, in the light type they are smaller and
pointing towards the antenna bases. Very large black spots
behind lateral ocelli, white cranium suture with large blackishpurple-red spot at the palmen body in both male and female, very
dark blackish-brown posterior edge. Our median ocelli spot on
the head capsule of light form is incorrect in shape.
Mouthparts; the female maxilla have 10 pectinate setae combs on
both the left and right side, with 31L-29R setae in the
submedial row with 10 in each row being none fimbriated in
nature. The male maxillae have 10 pectinate setae combs on the
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crown, and 27L-26R setae in the submedial row with 10 being none
fimbriated in nature. Mandibles; on the female there are, 7
teeth on the inner side of the outer left canine, and 0 teeth on
the inner side of the inner canine. On the right mandible there
are 5 teeth on the inner side of the outer canine and 0 tooth on
the inner side of the inner canine. On the male there are 6
teeth on the inner side of the outer left canine and 5 on the
right. Regarding the inner canine there are 0 teeth left and 0
on the right.
Labrum; has a fairly shallow indenture in the frontal margin,
fine dorsal setae all set forward of the ventral robust setae,
robust setae set back well from frontal margin with, a row of 4,
followed by 2 rows of 2, then 4 rows of 3.
Pronotum; shaped as others in the genus, having a small brown
coma spots on the anterior-lateral edge followed inward by large
pale spot in the same shape, followed by a large brown-black
spot in the same shape, a pale round spot in the submedial area,
with another small brownish-black coma ( spot. There are two
submedial yellow spots and a small one in the median area,
posterior edge brown.
mesothorax; pale pinkish median stripe with two large pinkishbrown coma shaped spots = ) scutellum appears very dark black in
color.
Mesosternum; pale white-yellow with many black markings, coxa
all marked with blackish spots, pleura streaks present.
Legs; overall like all others in the genus but having distinct
banding pattern from other forms.
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Abdomen tergum; narrow median stripe being lighter that all
other areas, often not connected to the posterior edge of each
tergite, continuous submedial stripes on all tergites that fully
intrude into the 10th which terminates with a black transverse
rectangular spot on the posterior edge, lateral edges pale from
1-7 followed inward by a series of dark stripes 1-7, then with a
pale sublateral streak with large black spiracular spots that
transcend into the adult stage.
Abdominal venter; the female is orange-yellow and the male is
yellow-white, both male and female have venter-lateral markings
from the 5th-9th and are shaped as in a coma. The posterior
1/3rd of the 9th with a brown transverse band from lateral edge
to lateral edge. There is a elevation in the median area of this
band thus creating the appearance of a crescent shape marking
rapping the 9th. There are (2) large prominent black spots on
the sublateral area of the posterior edge of the 9th in both the
male and female.
Tails; yellowish-brown with fine dark brown articulations.
Ohioense
Traver 1935
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First description
Dark types
Notes; In my 2014 rearing study of this form, the larva clearly indicate
two separate types of larva that will rear out as adult ohioense. The two
types are subject to specific substrates only. We are referring to these
two types as light type and dark type. Both of these types possess subequal lateral spines on the 8th and 9th segment of the larva abdominal
cavity. Because the light form aligns with Travers table and couplets in
the Biology of a Mayfly, the lighter form should be considered the
standard and the dark type the variant.
Lateral projection measurements 100X;
8th lateral projection average length; 7/100 mm
9th lateral projection average length; 11/100 mm
Female larva; 13 mm
Male larva;
9 mm
Tails;
Tails;
17 mm
15 mm
Dark form;
General
appearance
dark
blackish
discontinues submedial stripes, and
substrates.
brown
throughout
is only found on
with
dark
Head capsule; in both the male and female the head capsule is
highly depressed and oval in shape as in others in the genus, no
pale spot frontal margin, no pale spots in front of and lateral
to the antenna bases, ♥ shaped pale spot in front of the median
ocelli, with a large black spot in front representing a
midcrania spot in the adults. Antenna bases heavily shaded in
black, other than the extending pale stripe from the compound
eyes to lateral edges the entire lateral edge is black much like
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Heptagenia sp. Very large black comas thus = ( in front of each
compound eye as in candidum but extending further than antenna
bases and close to lateral edges, in the light type they are
smaller and pointing towards the antenna bases. Very large black
spots behind lateral ocelli, white cranium suture with large
blackish-purple-red spot at the pulmonary body in both male and
female, very dark blackish-brown posterior edge.
Mouthparts; the female maxilla have 10 pectinate setae combs on
both the left and right side, with 31L-29R setae in the
submedial row with 10 in each row being none fimbriated in
nature. The male maxillae have 10 pectinate setae combs on the
crown, and 27L-26R setae in the submedial row with 10 being none
fimbriated in nature. Mandibles; on the female there are, 7
teeth on the inner side of the outer left canine, and 2 teeth on
the inner side of the inner canine. On the right mandible there
are 5 teeth on the inner side of the outer canine and 1 tooth on
the inner side of the inner canine. On the male there are 6
teeth on the inner side of the outer left canine and 5 on the
right. Regarding the inner canine there are 2 teeth left and 0
on the right.
Labrum; has a fairly shallow indenture in the frontal margin,
fine dorsal setae all set forward of the ventral robust setae,
robust setae set back well from frontal margin with, a row of 4,
followed by 2 rows of 2, then 4 rows of 3.
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Pronotum; shaped as others in the genus, having a small gray
coma spots thus = ( on the anterior-lateral edge followed inward
by large pale spot in the same shape, followed by a large black
spot in the same shape, a pale round spot in the submedial area,
with another large black coma ( spot. There are two submedial
pink spots and a small one in the median area, posterior edge
very dark black-ish-brown.
mesothorax; pale pinkish median stripe with two large pinkishbrown coma shaped spots = ) scutellum appears very dark black in
color.
Mesosternum; pale white-yellow with many black markings, coxa
all marked with blackish spots.
Legs; overall like all others in the genus but having distinct
banding pattern from other forms.
Abdomen tergum; large wide median brown stripe from the 1st
through the 9th, with submedial pale discontinuous streaks
throughout all tergites, thus looking like coma shaped spots as
in gildersleevei, and candidum. These spots do not connect to
ether the anterior or posterior edge of each tergite, with
strong black shading on the posterior edges of the tergites as
in gildersleevei, pallidum. Pale lateral areas with black spots
from the 1st-6th, pale sublateral streaks shaped like a coma on
1st-6th, with a very small pale spots on tergum (7) in the
posterior lateral area. In the female there are large prominent
black spiracular spots on the 1st through the 9th. These spots
not so prominent on the male and are from the 2nd through the
9th. Pale submedial streaks are deeply intruded into the 10th
and the posterior edge is blackened by a transverse rectangular
spot.
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Abdominal venter; same as light type the female is orange-yellow
and the male is yellow-white, both male and female have venterlateral markings from the 5th-9th and are shaped as in a coma.
The posterior 1/3rd of the 9th with a brown transverse band from
lateral edge to lateral edge. There is an elevation in the
median area of this band thus creating the appearance of a
crescent shape marking rapping the 9th. There are (2) large
prominent black spots on the sublateral area of the posterior
edge of the 9th in both the male and female.
Tails; yellow-brown with pale brown articulations
Pallidum
Traver 1933
Notes; based on Traver 1933, Lewis 1974 and one photo that
aligns with Dr Travers description and can only be pallidum. We
have not handled pallidum as it is not in our geographical
range. A maculation morphology study of the entire genus allows
a very clear hypothesis. In the abdomen Traver says median spot
thus =() what that means is this shape
in the median area of
each tergite.
General appearance; slender small light reddish-brown lateral
projection equal in length.
Body size; 6-7 ♂ mm, 6-7.5 ♀ mm
Tail size; 10-11 mm
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Head capsule; brighter reddish-brown especially anterior to
ocelli meaning the area between the antenna bases, (very pale
darker areas at antenna bases to reflect dashes below antenna
bases on the clypeus in the adults). Pale areas from compound
eyes to lateral margins, (with small black spots in front of
compound eyes to coincide with adults), a pale spot in front of
median ocelli (likely ▼ triangular in shape).
Mouthparts; maxilla with 11-13 pectinate setae combs on the
crown, with approximately 25 setae in the sub medial row.
Mandibles with 5-8 teeth on the inner side of the outer canine,
and 2 blunt teeth on the inner side of the inner canine. All
other mouthparts would be indistinguishable from all others in
the genus. The labrum would be diagnostic as all other.
Pronotum; lateral areas hyaline brownish-red with pale areas
(and very fine blackish spots that will become thin black
stripes on adults).
Notum; similar to pronotum (likely with a paler median
longitudinal suture, and a pale area at the scutellum as in the
adults).
Legs; yellow-brown with alternating pale yellow and pale
reddish-brown bandings, tibia smoky at the apex, tarsus dusky,
(small black spots at the femora joint of all femora may be
absent on rear).
Abdomen; reddish-brown with very thin and fine pale submedial
stripes that do not stand out. Each median section of the median
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line shaped
and connected forming a median line, with very
narrowly blackened posterior tergite margins, lateral edges of
1-7 pale but not seen with gills and wing pads present, no
spiracular spots.
Ventral; pale yellow white with shaded brown lateral margins on
sternites 7-9
Tails; pale
throughout.
yellow-brown
at
the
base
pale
tan
to
gray
tan
Proximum
Traver 1935
First description
Notes; Traver (1935) establish some criteria that lead us to this form.
This description is based on many collected and reared samples that keyed
out as adults to this form described in the “Biology of a Mayfly” (1935).
The genital were also distinct.
General appearance; Brownish-black
dorsal median stripes.
Body size; 9-9.5 ♂ mm, 11 ♀ mm,
Tails; 18 mm
throughout
with
continuous
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Head capsule; oval in shape and depressed as in other forms and
species in the genus. Typically having many black marks. Often a
pale spot on the median frontal margin as in (frontale) and
other forms but not shaped like a spot rather shaped like a
short longitudinal stripe. Pale spot in front on median ocelli
often T or ♥ shaped.
Black spot sometimes present in front of this spot as to
coincide with a midcrania shading. Very faint small pale spots
present below and lateral to the antenna bases near the anterior
margin. Triangular-ish pale spots on either side of the lateral
ocelli, these spots extent to the lateral margin as in all forms
in the genus in the general shape of a stripe and or triangle
shape. Black markings in front of the compound eyes either tear
or coma shaped pointing to antenna bases. There are two black
spots on the vertex behind and close to the lateral ocelli.
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Posterior edge of head capsule dark brownish-black. Posterior
lateral area often grayish brown hyaline.
Mouthparts; On the crown of the maxilla there are most often 1011 heavy pectinate setae combs on the left and right 10 being
the average. Submedial row of setae has 28-32 setae and
typically 21 of them are fimbriated in nature. The mandibles
having 6 teeth on the interior side of the outer canine on both
the left and right side. Regarding the inner canine, in most
samples there are 2 teeth on the left and right. All other mouth
parts coincide with and are reasonably indistinguishable from
all other species and forms in the genus.
Labrum; the labrum of proximum is diagnostic to form. At 200X
there is an frontal margin indenture of .6/100th, and the first
or medial robust setae is 1.5/100th from the anterior edge,
typically 3, then followed outward by 10 a rows of 2 to the
anterior edge.
Pronotum; Similar to others in the group by having pale lateral
edges and a crescent shaped pale spot in the submedial region.
The remaining areas blackish-brown. Often having small black
marks in the posterior submedial area that coincides with
pronotum makings in the adult stages.
Mesonotum; Blackish-brown with small pale areas often having
dark lateral edges. Wing pads dark brownish with greenish-yellow
hue from the fully formed adult wings encapsulated.
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Mesosternum; Pale yellow, pleura marks are present at the
lateral edges between the rear and mid legs, and the mid leg and
the foreleg.
Foreleg; The femora in general having the appearance of banding.
There is a pale longitude band in the median area, laterally
followed by a dark band and then a very pale band at the
terminal end. Often a large black spot at the joint on the
dorsal side. Tibia; basil area dark brown at the joint with
black spots on the lateral edge, followed by a pale area,
another pale brown area and terminating at the tarsi joint as
pale yellow-whitish with a black spot. Tarsi marked as in tibia,
fore claws not denticulate. Black spot at the terminal end of
the tibia.
Middle leg; Median longitudinal stripe restricted to the
posterior edge followed by a pale stripe that is broken. Apex of
femora very dark. Tibia marked as in fore tibia with terminal
black spots.
Rear leg; Femora almost entirely brownish-black. Pale median
spots with a pale apex edge that has dark spots. The posterior
edge often having large dark spots that are restricted to the
posterior edge.
Abdomen dorsum; General appearance continuous medial stripes.
Lateral spines on the 8th shorter than the 9th. Medial dark brown
stripe generally equal in size from the 1st to the 10th. Slightly
wider on segments 3-8, most often lens shaped thus; (). Pale
submedial streaks somewhat uniformed slightly wider on the
segments 5-8, slightly reduced on the 9th.
Streaks deeply intruded into the 10th. Lateral edges most often
pale from 1-9. Sublateral areas having pale spots from the 4th
through the 7th. These spots often covered by the gill plates
giving the appearance of not having sublateral marks.
Small spiracular spots from the 2nd through the 9th. Tergum 3
often very pale from lateral edge to submedial streak binder
edge. Tergum 10 posterior and lateral edges blackish and very
dark.
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Abdomen Venter; Male and female both having venter-lateral
markings. In females these marks are most often from the 1st or
2nd segment through the 9th.
In males these marks are typically seen on the 6th through the
9th as in most in this genus. In females the abdominal cavity is
orange-yellow due to eggs present in the cavity.
In males most often yellow-white. These venter-lateral marks on
the 7th-9th looking much like dark brown comas.
The entire posterial region being ½ of segment 9 dark cinnamon
brown as a wide transverse band. May have slight anterior
elevation in the medial area.
In the female there may be medial ganglionic markings present
from the 3rd or 5th segment through to the 9th. The entire
posterior edge of the 9th blackish. Male claspers are typically
blackish-brown.
Tails; Blackish brown with pale articulations.
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Now let’s start with the illustrations of the larva. All
these markings are stated as they appear in the tables.
Starting with the head then moving to the abdomen.
1; pale spot on the frontale shelf
2; pale spot lateral to antenna bases
3; black spot lateral to antenna bases
4; spot in front of compound eyes
5; median crania spot
6; spot in front of median ocelli
7; spread of lateral ocelli
8; spots on the vertex of the head
9; black spots on the pronotum
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All these marks do transcend into the adult stages. Not
all the markings on the abdomen transcend into the adult
stage.
14; submedial abdominal stripes
15; blackened posterior edge of tergite
16; spiracular spots
17; lateral projections, referring to equal size of the
8th and 9th
18; submedial stripes entering the 10th segment
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Stenacron larva features and key
From darkest to lightest
Anatomical
Features
1
gildersleevei
dark form
ohioense
no
no
no
yes
yes
no
sometimes
yes
yes
spot in front of
compound eyes
median crania spot
SM blk spot
LRG coma
large coma
yes blk
yes blk
yes blk
6
shape of spot in
front ocelli
♣-ish
♥-ish
7
spread of lateral
ocelli
wide
very wide
wide
8
BLK spot vertex
SM black
LRG blk
LRG black
9
maxilla pect setae
10 - 11
11 - 13
10 - 11
10
25 - 30
30 - 45
28 - 32
11
setae submedial
row
MAND outer canine
6
7 - 9
7 - 8
12
13
MAND inner canine
BLK spot pronotum
0
yes
3 - 7
LRG
3 - 4
LRG coma blk
14
yes
no
no
15
submedial streaks
continuous
tergites blackish
no
yes
yes
16
spiracular spots
no
yes prom
yes
17
8&9th spines =
equal
equal
sub-equal
18
streaks entering
10th
tail color + ART
yes
minute
minute
yellow
dark with
art
blk-ish
2
3
4
5
19
pale spot frontale
margin
pale spot ant
bases
BLK spot ant bases
canadense
Currently there is only (1) key to larva being the lateral projection
on tergites 8-9. However the mouthparts being maxillae & mandibles
are considered diagnostic Lewis 1974.
Larva must be measured while alive abdomens expand at death
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Stenacron larva features and key
From darkest to lightest
Anatomical
Features
light form
ohioense
frontale
pale spot frontale
margin
pale spot ant
bases
BLK spot ant bases
spot in front of
compound eyes
median crania spot
shape of spot in
front ocelli
stripe pale
yes
yes
LRG yellow
yes
yes
no
tear drop
yes
small coma
♥ - ish
yes
SM tear
drop
yes
-ish
7
spread of lateral
ocelli
wide
wide
wide
8
9
BLK spot vertex
maxilla pect setae
LRG blk
10
LRG blk
9 typical
LRG blk
9L - 10R
10
25 - 30
39 - 46
34 - 35
11
12
setae submedial
row
MAND outer canine
MAND inner canine
6
0
6 - 7
2 - 4
6L - 7R
0
13
BLK spot pronotum
yes
small blk
yes
14
submedial streaks
continuous
tergites blackish
spiracular spots
8&9th spines =
streaks entering
10th
tail color + ART
yes
yes
no
no
yes LRG
sub-equal
deeply
intruded
yellow + art
no
small
equal
minute
no
yes LRG
equal
deeply intruded
dark + art
dark + art
1
2
3
4
5
6
15
16
17
18
19
sometimes
majus
yes
T - ish
Currently there is only (1) key to larva being the lateral projection
on tergites 8-9. However the mouthparts being maxillae & mandibles
are considered diagnostic Lewis 1974.
Larva must be measured while alive abdomens expand at death
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Stenacron larva features and key
From darkest to lightest
Anatomical
Features
proximum
conjunctum
pale spot frontale
margin
pale spot ant
bases
BLK spot ant bases
spot in front of
compound eyes
median crania spot
shape of spot in
front ocelli
pale stripe
no
yes
yes
LRG yellow
unknown
yes
SM coma
LRG blk X 2
smeared
tear drop
yes
unknown
unknown
7
spread of lateral
ocelli
8
9
10
1
2
3
4
5
6
♥ - ish
unknown
unknown
tight
tight
unknown
BLK spot vertex
maxilla pect setae
setae submedial
row
MAND outer canine
MAND inner canine
BLK spot pronotum
yes sm blk
10 - 11
28 - 32
LRG blk
10
34 - 37
unknown
9 - 10
30 - 40
6
2
sm blk
6 - 7
1 - 2
sm blk
6 - 7
3 - 4
nk
yes
no
yes
15
submedial streaks
continuous
tergites blackish
no
no
no
16
17
spiracular spots
8&9th spines =
small
8th shorter
moderate
equal
LRG distinct
unknown
18
streaks entering
10th
tail color + ART
moderate
minute
short
yellow + art
dark + art
lt brown + art
11
12
13
14
19
faint
T - ish
minnetonka
Currently there is only (1) key to larva being the lateral projection
on tergites 8-9. However the mouthparts being maxillae & mandibles
are considered diagnostic Lewis 1974.
Larva must be measured while alive abdomens expand at death
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Stenacron larva features and key
From darkest to lightest
Anatomical
Features
1
2
3
4
5
6
pale spot frontale
margin
pale spot ant
bases
BLK spot ant bases
spot in front of
compound eyes
median crania spot
shape of spot in
front ocelli
candidum
carolina
pallidum
no
no
no
sm yellow
no
no
blk shading
coma
no
blk shading
no
sm slash
prominent
- ish
yellow
T elongated
no
T-ish
7
spread of lateral
ocelli
wide
wide
wide
8
BLK spot vertex
yes blk sm
yellow
yes
9
10
maxilla pect setae
setae submedial
row
MAND outer canine
MAND inner canine
BLK spot pronotum
7 - 8
15 - 25
10
20 - 30
11 - 13
25
7 -8
0
LRG coma blk
7 - 8
2 P-Blunt
sm gray
5 - 8
2
pale gray
no
no
yes very fine
no dark-ish
yes distinct
8th shorter
minute
no
no
9th longer
moderate
yes
no
8th shorter
minute
dark + art
smoky = art
smoky brown
11
12
13
14
15
16
17
18
19
submedial streaks
continuous
tergites blackish
spiracular spots
8&9th spines =
streaks entering
10th
tail color + ART
Currently there is only (1) key to larva being the lateral projection
on tergites 8-9. However the mouthparts being maxillae & mandibles
are considered diagnostic Lewis 1974.
Larva must be measured while alive abdomens expand at death
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Stenacron larva features and key
From darkest to lightest
Anatomical
Features
1
pale spot frontale
margin
2
pale spot ant
bases
BLK spot ant bases
spot in front of
compound eyes
median crania spot
shape of spot in
front ocelli
spread of lateral
ocelli
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
areion
affine
larva
unknown
unknown
flaveola
same as interpunctatum Say
unknown
unknown
minute blk
no
♣ - ish
unknown
BLK spot vertex
maxilla pect setae
setae submedial
row
MAND outer canine
MAND inner canine
BLK spot pronotum
very small
unknown
unknown
submedial streaks
continuous
tergites blackish
spiracular spots
8&9th spines =
streaks entering
10th
tail color + ART
yes
unknown
unknown
no
no
no
equal
unknown
brow-yellow
Currently there is only (1) key to larva being the lateral projection
on tergites 8-9. However the mouthparts being maxillae & mandibles
are considered diagnostic Lewis 1974.
Larva must be measured while alive abdomens expand at death
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Stenacron larva features and key
From darkest to lightest
Anatomical
Features
1
2
3
4
5
pale spot frontale
margin
pale spot ant bases
BLK spot ant bases
spot in front of
compound eyes
median crania spot
heterotarsale
floridense
no
no
no
yes LRG yell
no
minute
no
no
sm slash
blk
no
LRG yellow
no
very minute
no
interpunctatum
no
fleur-de-lis
♣
tight
- ish
♣ - ish
very wide
moderate
BLK spot vertex
maxilla pect setae
setae submedial row
MAND outer canine
MAND inner canine
BLK spot pronotum
minute blk
9
30 - 35
5 - 7
3 - 4
minute tan
sm blk
8 - 9
20 - 25
7
4
very small
minute blk
9 -10
25 or less
7
4
slash minute
yes
no
yes + wide
15
submedial streaks
continuous
tergites blackish
no
no
no
16
17
spiracular spots
8&9th spines =
no
equal
no
unknown
no
equal
18
streaks entering
10th
tail color + ART
deeply
intruded
pale yellow
minute
moderate
pale brown
pale yellow
6
shape of spot in
front ocelli
7
spread of lateral
ocelli
8
9
10
11
12
13
14
19
Currently there is only (1) key to larva being the lateral projection
on tergites 8-9. However the mouthparts being maxillae & mandibles
are considered diagnostic Lewis 1974.
Larva must be measured while alive abdomens expand at death
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Stenacron
Mayflies
Adults 2020
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Who is Who?
We bet you are having a hard time with who is who even in this
larger than life test. Can you tell which is the real true to
form interpunctatum Say 1839, not likely? By the time you finish
with this book you will be able to see who is who. The samples
you are looking at are nearly 3X the real size.
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Adults
Table of contents
Who is Who ? ………………………………………………………………………………………………… 265
Table of content………………………………………………………………………………………… 266
Characteristics of adults………………………………………………………………… 268
Collecting adults……………………………………………………………………………………… 268
Male or female……………………………………………………………………………………………… 269
Interbreeding………………………………………………………………………………………………… 269
Variation and maculation…………………………………………………………………… 271
Eggs and eyes………………………………………………………………………………………………… 273
Taxonomic confusion………………………………………………………………………………… 298
Photo plates…………………………………………………………………………………………………… 283
Adult anatomy………………………………………………………………………………………………… 295
Comparative discussions……………………………………………………………………… 306
Male general side view illustrations…………………………………… 321
Female side views……………………………………………………………………………………… 322
Full male adult abdomen……………………………………………………………………… 324
Top view of thorax illustrations……………………………………………… 327
Side view of thorax illustrations…………………………………………… 331
Head illustrations…………………………………………………………………………………… 334
Forewing illustrations………………………………………………………………………… 336
Couplets……………………………………………………………………………………………………………… 337
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Complete descriptions…………………………………………………………………………… 344
Affine………………………………………………………………………………… 344
Areion………………………………………………………………………………… 348
Canadense………………………………………………………………………… 351
Candidum…………………………………………………………………………… 355
Carolina…………………………………………………………………………… 358
Conjunctum……………………………………………………………………… 361
Floridense……………………………………………………………………… 363
Frontale…………………………………………………………………………… 367
Gildersleevei……………………………………………………………… 370
Heterotarsale……………………………………………………………… 373
Interpunctatum Say………………………………………………… 377
Majus…………………………………………………………………………………… 381
Minnetonka……………………………………………………………………… 385
Ohioense…………………………………………………………………………… 388
Pallidum…………………………………………………………………………… 391
Proximum…………………………………………………………………………… 394
Table of features and keys……………………………………………………………… 397-404
Credit for usage of photos……………………………………………………………… 405
Pronouncing names and words…………………………………………………………… 406-409
Selected bibliographies……………………………………………………………………… 411-417
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Characteristics of the adult in genus
All Stenacron in the adult stages have a signature genetic
feature that is used to classify the adults. In the middle area
of the forewing there is typically a black dash or spots as seen
in the illustration below.
This dash can be just a single spot which is only found in one
species in the genus being Stenacron candidum. In most samples
it will be a black bar typically covering 2-3 cross-veins in the
R1&R2 interspaces. By using this character you can establish
that your sample is in fact a Stenacron.
Collecting adults
Collecting Stenacron adults is difficult for several reasons.
First they typically hatch sporadically and in small numbers. So
finding a spinner fall can be hard, unless you are collecting
near a larger slower moving river. It will most always come down
to you being in the right place at the right time.
Second the spinner fall often takes place after dark and over
very shallow slow moving waters near the banks. They are often
found resting on the underside of a leaf waiting mating time.
Stenacron as a rule hatch with the greatest numbers being
female.
In our rearing studies we have found that the ratio is
females per 1 male. In captivity the females can survive
days, but the males expire often in less than 60 hours.
there is not a spinner fall every day; every third day
likely.
about 9
up to 7
Usually
is more
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Rearing the larva is not hard and is the best way to collect
adults. Stenacron Mayflies part II; will cover this process in
detail.
Male and female
Here are some easy technics to tell if your samples are a male
or female. Size is one way to tell the females are much larger
than the males. Next most females have an orange colored abdomen
because of the eggs they carry.
The most noticeable feature is the head shape and size. The
first illustration is the head of the female. Right below that
is the head of the male.
The males have very large compound eyes that are close together,
while the females have small compound eyes spread very far from
each other.
If you know how to identify by genitals you can also use the
claspers at the posterior area of the 10th to tell them apart.
Female
male
Interbreeding
From personal observations in both collecting and careful
rearing interbreeding is inconclusive. None of the previous
authors have given definitive proof of this. It is however a
very reasonable concept.
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Even with the newest morphological information one must still
wonder if there really are any hybrids out there. So for a
moment let’s assume that the hybrid possibly has merit, and
could happen. We will need to have a hypothetical view point
because there is no true evidence of the hybrids. Let’s first
look at the life cycle or life history of the genus. Unlike many
mayflies, Stenacron are more generally known for hatching in
sporadic and smaller numbers. Reports do however indicate that
they can hatch in greater numbers on some river systems. Those
rivers that are generally slower and larger can support much
bigger populations. So with less numbers on an average it seems
not only plausible but sensible to conceive that interbreeding
could take place. Most Stenacron male
Imagoes commonly expire within several days, and ohioense has
shown itself to expire in less than (60) hours in captivity. So
as a survival mechanism to the overall health of the genus the
hybrid becomes more sensible. Life can be said as, “it just
finds a way” and it often does just that. A hypothetical
scenario would be. If inside a spinner fall there are 50
frontale males and 50 frontale females we could presume that all
the females would copulate and deposit eggs as being the form
frontale.
However if we change the female ratio to 25 of them are now
frontale, 10 of them are now gildersleevei, 15 are conjunctum.
Do we now presume that the gildersleevei will die, and not
copulate with a frontale male?
For that part of the experiment DNA would likely be the only way
to truly know, and it may not offer a true or clear answer. As a
survival mechanism the females can hold a fertile position
longer until copulation can be achieved. Many reared ohioense
female can last up to 5 days in captivity, and in the real world
they may last up to a week. The hatching ratio of male to female
adults in my rearing of ohioense
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clearly indicates 9 females to 1 male. So under sporadic
hatching the female may have to wait even longer till a male is
mature and able to mate.
As to the female conjunctum being what is already considered a
hybrid form, I suspect that it is plausible that it could mate
with the frontale male, if there were no others of that form
available.
With smaller populations it does not seem likely they would
allow themselves to expire, if they did it could put the entire
genus at risk of survival as a whole in low percentage areas
only. If there really are any hybrids out there that would just
make this genus even more interesting and special. Why can they
interbreed but yet no other genus is thought to have that
ability?
Even with the Leopard larva changing its spots, the hybrid
thinking will always remain a mystical mystery of this unique
and special genus. It’s like a great conspiracy theory.
With new evidence there are likely no true hybrids and the
mystical legend of interbreeding will likely live in the legacy,
of this amazing genus forever.
Variation and Maculation
From personal observations in both collecting and careful
rearing interbreeding is inconclusive. None of the previous
authors have given definitive proof of this. It is however a
very reasonable concept.
Even with the newest morphological information one must still
wonder if there really are any hybrids out there. So for a
moment let’s assume that the hybrid possibly has merit, and
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could happen. We will need to have a hypothetical view point
because there is no true evidence of the hybrids.
Let’s first look at the life cycle or life history of
Unlike many mayflies, Stenacron are more generally
hatching in sporadic and smaller numbers. Reports
indicate that they can hatch in greater numbers on
systems. Those rivers that are generally slower and
support much bigger populations.
the genus.
known for
do however
some river
larger can
So with less numbers on an average it seems not only plausible
but sensible to conceive that interbreeding could take place.
Most Stenacron male
Imagoes commonly expire within several days, and ohioense has
shown itself to expire in less than (60) hours in captivity. So
as a survival mechanism to the overall health of the genus the
hybrid becomes more sensible. Life can be said as, “it just
finds a way” and it often does just that. A hypothetical
scenario would be. If inside a spinner fall there are 50
frontale males and 50 frontale females we could presume that all
the females would copulate and deposit eggs as being the form
frontale.
However if we change the female ratio to 25 of them are now
frontale, 10 of them are now gildersleevei, 15 are conjunctum.
Do we now presume that the gildersleevei will die, and not
copulate with a frontale male?
For that part of the experiment DNA would likely be the only way
to truly know, and it may not offer a true or clear answer. As a
survival mechanism the females can hold a fertile position
longer until copulation can be achieved. Many reared ohioense
female can last up to 5 days in captivity, and in the real world
they may last up to a week. The hatching ratio of male to female
adults in my rearing of ohioense
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clearly indicates 9 females to 1 male. So under sporadic
hatching the female may have to wait even longer till a male is
mature and able to mate. As to the female conjunctum being what
is already considered a hybrid form, I suspect that it is
plausible that it could mate with the frontale male, if there
were no others of that form available. With smaller populations
it does not seem likely they would allow themselves to expire,
if they did it could put the entire genus at risk of survival as
a whole in low percentage areas only. If there really are any
hybrids out there that would just make this genus even more
interesting and special. Why can they interbreed but yet no
other genus is thought to have that ability?
Even with the Leopard larva changing its spots, the hybrid
thinking will always remain a mystical mystery of this unique
and special genus. It’s like a great conspiracy theory. With new
evidence there are likely no true hybrids and the mystical
legend of interbreeding will likely live in the legacy, of this
amazing genus forever.
Eggs and eyes
One of the most fascinating things in nature is mate selection.
In life many animals they are attracted to their mates by smells
or pheromones. Because the male compound eyes are so sensitive
to light definitions we felt that color definitions may be
important. It is also unclear how much of their overall eyesight
is based on the simple eyes or ocelli, or the larger compound
eyes. First let’s take a look at the face and head of a male
interpunctatum / ohioense
dark type subimago
under the
microscope. Notice the full smile on the frontal margin.
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As mentioned we did review of about 50 females eggs from 6
different forms. There is very slight variation in the color
density and brightness in the dark form to the lighter forms. To
the human eye the variation is not really high. There is quite a
bit of color variation in the abdominal color of the egg
carrying females. There is little question that the lighter
species and forms have yellowish colored eggs. We were unable to
locate S carolina that has yellow-cream colored eggs. So we
worked with samples that were available in our geographical
region to see if the males may use color definition in the mate
selection process. Let’s first take a close up look at an
illustration we made of a typical female Stenacron egg.
Although there were slight differences in the eggs we had no way
to describe the very slight differences and if what we saw was
of any value. There was one primary difference that was notable.
The size of the eggs from pole to pole or left to right and in
the top to bottom in the above illustration.
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There was slight variation in size in the different forms.
However the size differential range was .2/100 to .5/100 @ 200X.
We do feel that a true study of eggs would be worthwhile from
someone like Dr Richard W Koss with great egg expertise. Now we
will look at pictures of females we verified to males and larva
exuvia to see the slight color difference.
Stenacron interpunctatum / heterotarsale
Stenacron interpunctatum / conjunctum
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Stenacron interpunctatum / proximum
Stenacron interpunctatum / ohioense
It is pretty clear that the value of difference to our eyes is
very little. We did perform a color range assessment on the male
subimago and male imago’s and found they were more responsive
and attacked to variable hues of orange. What we did was place
two paint chip cards with two different hues of orange to their
left and right to see if the males were more attracted to one
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than the other, and it turns out that more than 70% of the time
they picked the same color. We did this test with multiple cards
inter mixing them. They showed the greatest attention to hues on
the card sample# 3. If we picked card 1 and card 5 most times
they were indecisive and wouldn’t make a choice. If we picked 4
and 3 they sometimes had a difficult at times making a choice.
Color # 3 was chosen the most, but number #4 was also chosen
often. Interpunctatum Say did tend to prefer sample 5. We never
data logged this little curiosity experiment we wanted to see
what would happen. So is color part of the selection process it
is tough to say but this is very suggestive.
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Taxonomic Confusion
Taxonomic confusion has plagued this genus most of its
existence. There are two different time frames for confusion.
Pre 1935 & post 1935. Why is the year 1935 so important to the
understanding of this genus? In 1935 The Mayfly Bible was
written, by Dr Needham, Dr Traver, Dr Hsu wrote The Biology of a
Mayfly. As this book was being written Dr Needham requested that
Dr Traver synonymize affine to heterotarsale and they have been
together since. They have never been re-reviewed to this day
even though there is a 2 mm size difference, and we believe the
labrums of the larva are also likely different based on
environmental needs. Quoting Dr Traver page 303 of my 1935 first
addition of the Biology of a Mayfly under larva table. “Assuming
affine equals heterotarsale”. That sounds like she was skeptical
of this new synonymy.
There was a fair amount of confusion prior to this like Clemens
1913 canadense, and the soon to be ohioense 1935, regarding
spiracular spots on the abdomen of the larva. This is part of
the reason we believe Dr Traver erected ohioense to bring
clarity and isolation to it from canadense. Let’s look at the
larva that Clemens was looking at. Here is a sample of a female
canadense that’s why it has the orangey coloring in the abdomen
as there are eggs present. On the right is ohioense the
spiracular spot do not stand out that much at a distance. The
size of the median line on the abdomen is the primary viewing
difference canadense has a thin and tight line, with wide
submedial stripes. Ohioense has a wider medial stripe, and
narrower submedial stripes.
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The key to separation without killing and dissecting is the
lateral projections of the 8th vs 9th. On canadense the 8th and 9th
lengths are equal. In ohioense they are sub-equal as per Traver
1935 meaning the 8th is slightly shorter. The difference is
small but visible under a dissection microscope at a low power
or by a 5X magnifier loop. The biggest difference is when we
just view the abdomens. Here we have canadense on the left and
ohioense light type on the right, matching Traver 1935
description or historical profile.
When you look close at the above illustrations you will see more
differences than commonality. What is really striking is the
sublateral stripes or series of pale spots on each segment near
the gills. On ohioense they are often not seen, and on canadense
they almost form a complete secondary stripe. Looking at this it
is not hard to see why Clemens and others had a difficult time
with the larva. Actually F P Ide 1935 did an excellent paper on
development of postembryonic canadense larva. This was very
helpful with larva understanding.
Now let’s move over to post 1935 taxonomic confusion. In 1947
Spieth did something radical and unjustifiable he synonymized
ohioense into canadense and rewrote a new description for
canadense to include ohioense and spiracular spots. Why is that
so damaging to the genus. Ohioense has spiracular spots and
canadense does not.
To further complicate things he also synonymized his new
canadense
profile
to
the
frontale
complex
now
inside
interpunctatum Say. Looking at a typical canadense male adult
left, then a typical ohioense male adult on the right although
very similar there are distinct differences.
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Other than the spiracular spots distinction is moderately
difficult. The first thing besides the spots that stands out is
the very dark notum or top of the thorax. Canadense is typically
very dark chocolate brown and ohioense is more reddish with a
dark germinate or incomplete median notum stripe. Here is a
dorsal view of the notum’s to clarify this.
However the adult male genitals are very far from each other.
From the overall shape, to the spine cluster size, and shape of
the lateral-dorsal spine cluster. The basal or sublateral spines
on ohioense are 3 or less, and on canadense there typically 4-6
often making a small basal sublateral spine cluster looking like
interpunctatum Say. Most true canadense samples will have 2 sets
of dorsal mesal spines plus apical spines.
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Historically every description for canadense true to form being
Walker 1853 canadense through Traver 1935 descriptions do not
have spiracular spots on the lateral areas of each abdominal
segments. This first illustration for canadense shows the lack
of spots. The illustration below is for true to form ohioense
with a red arrow pointing to the spiracular spots.
canadense Walker 1853
ohioense Traver 1935
In 1935 Dr Traver erected ohioense, proximum, majus, conjunctum,
gildersleevei, and candidum. Without a doubt this was the
largest contribution to the genus. Since that time gildersleevei
and candidum have continued to be considered valid species
concepts as they are very distinct from all others in the genus.
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There is no question that looking at it from Spieth’s view in
1947 the following can look very similar. Frontale, proximum,
conjunctum, majus, and even ohioense in the light type of the
form. We can see his reasoning for creating a frontale complex,
but Spieth’s error was synonymizing this dark group into
interpunctatum Say 1839.
If he had have worked with more than fore tarsal ratio, forewing
size, the age of the species in priority of name he could have
made a valid species concept for Banks frontale 1910 including;
frontale, ohioense, proximum, conjunctum, and majus, and left
Walker 1853 canadense as a valid species. If he had of done that
there would be no misunderstandings or taxonomic confusion from
1947 till 2017 and his hybrid concept would have looked even
more legitimate. All of the following disagreed with Spieth 1947
and so do we.
•
•
•
•
•
G
L
B
P
S
F Edmonds
Berner
D Burks
A Lewis
L Jensen
(genus)
That is a big group of very important taxonomist that disagreed
with Spieth’s conclusions. Lewis 1974 The Taxonomy and Ecology
of Stenonema Mayflies made a big effort to break apart some of
Spieth’s work. It was Lewis that made larva diagnosis more
possible by stating mouthpart tooth counts for many of the forms
and species. Berner paved the way in 1950 with the publication
and first usage of mouthparts in the genus in the book The
Mayflies of Florida. What was missing now was forms like
ohioense, proximum. conjunctum, and majus. From close isolation
rearing, Traver 1935 descriptions, Spieth’s synonymy study, Burk
1953, and Lewis 1974, cataloguing the larva was not too hard.
Filling in the blanks was easily done by rearing larva,
identifying the male adults, and then retracing and documenting
the form back to the larva from the exuvia. From that point
doing a large mouthpart morphology study was easily done. On
average there were about 30 of each form dissected and
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catalogued per form. This gave us a solid average tooth,
pectinate setae comb, and setae in the submedial row count to
work with. All this information was placed in the tables in the
back of the larva book. There are also tables in the adult book
that reflect the features and keys to them. Breaking down the
interpunctatum complex into 3 basic groups as per Needham 1935,
Spieth 1947, and Lewis 1974 this is what it basically looks like
from very simple view.
Group A interpunctatum Say; Lewis 1974 new Syn
• interpunctatum Say + areion
Group B heterotarsale; Needham 1935
new Syn
• heterotarsale + affine
Group C frontale;
Spieth 1947
new Syn
• frontale
• canadense + ohioense
• proximum
• conjunctum
• majus
Now let’s compare true interpunctatum Say 1839, against
proximum, and ohioense so you will quickly see why most people
do not have any idea what the (true interpunctatum Say 1839)
looks like. As you can see they have nothing in common but fore
tarsal ratio as per Spieth 1947. Between our studies, Traver
1935, Burks 1953, Lewis 1974, and current DNA, we see many
reasons for this complex to be completely restructured.
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Photo Plate
Photo of a male and female when available
Female imago Interpunctatum / canadense
Female imago Interpunctatum / canadense
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Female imago Interpunctatum / frontale
Male imago Interpunctatum / frontale
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Female subimago Interpunctatum / proximum
Male subimago Interpunctatum / proximum
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Female subimago Interpunctatum / ohioense
Male subimago Interpunctatum / ohioense
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The following carolina photos are by Sharon Moorman and are
without question Stenacron carolina male imago. To show how to
quickly identifying this male is we must look at the head. First
is a photo interpunctatum / ohioense dark type, all others in
the genus have this head shape. In the head shape of carolina
notice how wide spread the compound eyes are from each other.
This can cause confusion with Maccaffertium, Heptagenia, and
Luecrocuta as many samples of carolina may have very little to
no pigmentation in the R1&R2 interspaces of the forewings.
Moreover all Stenacron have less pigmentation in the left wing
than the right. If markings are faint use the right wing for
genus conformations. Another thing to note very fine pronotum
streaks and black ringed at the bases of lateral ocelli as in
interpunctatum Say 1839.
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Over apex
Left forewing male carolina stigma stain over apex
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Other identification descriptive factors are by Traver 1935. All
Sternites are banded in smoky gray tones that wrap from the
terga bands breaking at the spiracles then reforming and
continuing around from lateral edge to lateral edge see ventral
photo below on the posterial margins see red arrow. This is
often more prominent on sternites 2-5. In this photo you can see
the right wing is more pigmented in the R1&R2 interspaces. There
is also commonly faint yellow shading on the posterior and apex
areas of the hindwings with light smoky edge. The stigma stain
clearly continues over the apex of the forewing as in most forms
and species in the genus.
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100% positive identification of females is hard in person let
alone from a photo. The credibility of the source must be
considered as part of the equation. Sharon Moorman has proven
reliable in many identifications. With that said she stated
several times that this sample was digitally measured to be 7.5
mm. There is only one Stenacron female that size in the genus
being Stenacron pallidum. We have read and re-read Traver 1933,
1935, 1937 and find these photos align with great confidence. We
can even see the dumbbell shaped black spot in the forewing as
per Traver 1933 and stigma stain going over the apex of the
forewing.
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Source Sharon Moorman; Lewis 1974 is the only proper description
of this species. Berner 1986 mayflies of Florida did cover it
but more on ecology. Floridense is the only species or form in
this genus with a reddish elongated spot on the vertex of the
head. No measurements were taken. However based on Lewis
regarding this spot, pale or no spots on the frontal margin, and
black ringed ocelli the likely hood of this being floridense is
very high. If we could with assurance place this as floridense
it would go to range extension as this is from; La Follette/
Norris Lake, Campbell County, Tennessee, USA. This is a moderate
sea level elevation.
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Here
we
wish
to
present
two
photos
that
are
close
representations of two forms in the genus. Photo one is from
Charley Eiseman Black River, Wisconsin, USA. The first sample we
are very sure could only be minnetonka, for several reasons.
The most important is there is no sign of even potential pleura
streaks, and the spiracular spots are very prominent. The next
is the reddish tinge on the 8th-10th tergites on the dorsal side
and surrounding the notum.
We will compare to our illustration made from Daggy 1945, Burks
1953, Lewis 1974. Most important is the collection location is
within 150 mile of Daggy’s holotype.
Also from Charley Eiseman is a sample he photographed in
Nashville, Tennessee, this is only about 250 miles from Oakwood
IL where Burks collected areion. This sample is a reasonable
variation that aligns with Burks 1953 with a high degree.
Looking very close at the rear tergites 6-9 there is a very
slight orange hue in front of the transverse dark bands. We are
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not saying this is areion but the photo is very suggestive. We
are also showing our illustration made based on Burks 1953, and
Lewis 1974 discussions. We have also seen on sites many that are
very bright orange. I personally believe Burk’s areion is a real
and heavily over looked form.
The only photo of Travers affine taken by Brando Woo at the
Cornell collection.
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Adult Anatomy
Top view of thorax to head, notum view
Clypeus
Lateral ocelli
Antenna
Cranium suture
Compound eyes
pronotum
Forewing root
mesonotum
Parapsides
scutellum
♀
Lateral scutellum
plate
Median notum stripe
longitudinal suture
Post scutellum
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Side view of thorax or pleura
pronotum
Lateral ocelli
ANi; anteronotal transverse impression
Mesonotum
Frontale
shelf or
Scutellum
clypeus
Rear wing root
Frontal margin
♀
Forewing root
coxa
femora
trochanter
Breathing spiracles
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Female and male heads
Vertex
Palmen body
Cranium suture
Black spot on vertex
Black ringed ocelli
♀
Flagellum
Small spot on
compound eye
Pedicel
Scapus
Dash below antenna
Clypeus
Mid-crania spot
Frontal margin
Mid-crania shading
Mid-crania structure
♂
Median ocelli or Simple eye
Lateral ocelli or simple eye
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Costal vein
bulla
Sub costal vein
Radius 1
Stigma stain
Radius 2
Intercalary
♂
Stigma stain over apex
Genus signature black dash R1&R2
Costal brace
♂
Stigma stain
Cross-veins
Not over apex
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Female and male abdomens
Submedial spots
Transverse shading
Medial stripe
Germinant medial stripe
♀
Oviduct
Spiracular spots
Sub-lateral shading
Transverse shading
tails
Transverse bands
♂
Genitals
Spiracle folds
Breathing
Spiracles
Claspers
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Foreleg described with fore tarsal ratio
Apical band
Tarsal 5 parts
Median band
Tibia
claw
Femora
coxa
Trochanter
Tarsal
Segment 2
Segment 1
The foreleg is made up of the following components. The coxa is
technically part of the thorax and the leg is connected to the
thorax by it. The trochanter is like an elbow that rotates and
it connects the coxa to the femora. The femora is connected to
the tibia, the tibia is connected to a multipart tarsal section,
finally with a small foot like claw. The tarsal area is divided
into
5
sections.
Historically
and
in
many
geneses
the
measurement of section 1 compared to section 2 of the tarsal is
very valuable in species concepts. A fore tarsal ratio is how
big the 1st section is compared to the 2nd. We are using a simple
percentage because everybody can see it, and use it. It’s like
cutting a pie in pieces.
For tarsal ratio in this genus went through all kinds of changes
from the late 1800’s to the 1970’s. As science became more
detailed and more complex ratios replaced simplicity. Things
started out as simple as (first segment slightly shorter than
second) to having a range of (first = 40% the length of second)
to (3-5th the length of the second) and finally (1.6-3.3).
This can be very complicated for someone learning. Dr Traver set
a excellent understandable ratio by stating simply 40% the
length of the second. With fore tarsal ratio being variable in
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Stenacron we will go with Dr Traver simple method of percentages
Everybody can then understand with ease. The table below shows
just how close the size is in the entire genus being 40-50%
range. This does not make it useless it is just another tool to
aid the diagnostic process.
Moreover she described all but, affine, minnetonka, areion, and
floridense to work with. All percentages given are from original
historical profile Lewis 1974 minnetonka, and floridense we
reversed engineered the numbers to a percentage, and did the
same forward to give ratios to older forms that didn’t have a
real ratio.
Stenacron fore tarsal ratio and percentage conversion table;
Form
Affine unknown
Areion
Canadense
Candidum
Carolina
Conjunctum
Floridense
Frontale
Gildersleevei
Heterotarsale
Interpunctatum
Majus
Minnetonka
Ohioense
Pallidum
proximum
Max
----3-5th
3.0
------------2.4
3.2
2.3
1.9
3.5
-------------------------
Min
Mean
------------2.0
------------------2.0
1.6
1.7
1.1
2.2
--------------------------
-----2.630
2.340
2.4
2.5
2.6
2.2
2.370
1.992
1.570
2.630
2.4
2.4
2.0
2.4
2.4
length of 1st %
Likely 45%
35-40%
40%
50%
50-55%
35-40%
40-45%
50-55%
45%
45%
35-40%
50%
50%
45%
50%
50%
So you could say for floridense that the 1st segment equals about
40-45% the length of segment 2.
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Male Genitals Spines Explained
Mesal spine
Apical spine
Terminal spine
Lateral spine cluster
Basil spine cluster
Dorsal lateral spine
Median apical area of lobe
Penal lobe
Curved axial spines
Floridense only
2-4
Basal or base of lobe
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Comparative Discussions
Having a section on comparative discussions is very helpful in
many ways. First is it the best opportunity to get to know them
all and what makes one different from the other.
In the past this has only to a degree been accomplished in a lab
with a large series of samples. However without a very clear
picture of what all the forms looked like under their historical
profile, being the original description, the range of variation
is very high and easily misunderstood.
This section is all about putting the two most difficult side by
side and seeing and discussing the differences. Although they
may at first glance look almost identical there is why more to
separate them than there is making them look the same.
Some samples we didn’t even include the opening of what they
have in common cause the list was too long. It was more
effective to focus on what the differences are in more detail.
Try to view all Stenacron to a specific form rather than species
you will find species from finding form. Keep the substrate in
mind, the darker the sample the darker the substrate and the
higher the altitude was. High variation in form is not from
hybrids it caused by their specific ecology.
Remember the adult is a mere temporary reflection of the
yearlong larva stage and the pigmentational maculation platform
does transcend from the larva to the adult stages.
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(Stenacron interpunctatum / canadense)
(Stenacron gildersleevei)
These two adults can be very similar especially the females and
have a lot in common. The male of canadense is much lighter in
the abdomen than the gildersleevei and the male canadense is not
as likely to be confused. In the female canadense the abdomen is
commonly very dark in maculation.
Features commonly shared in the two are;
larger overall size, transverse black band on the frontal shelf
from compound eye to compound eye forming a somewhat complete
smile, black spots on the vertex of the head, large black spots
on the pronotum, black triangle spots on the mesonotum right
behind the pronotum, longitudinal median stripe on the entire
notum area, black marked scutellum, black spots on the fore-coxa
area, heavily banded hind femur and a strong median band
present. Abdomen, Median black stripe on the dorsum of each
tergite 1 through 9, heavy submedial, sublateral, and transverse
band shading often blackish in color.
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Defining features to separate are;
Size, gildersleevei is larger, with no pleura streaks, stigma
stain is darker and going over the apex of the forewing on
gildersleevei, fine and smaller pale spots on submedial and
sublateral areas of all tergites, gildersleevei having large
fine defused spiracular spots that can be very hard to see and
are
often
encapsulated
inside
sublateral
and
transverse
abdominal shading. Canadense has no spiracular spots present,
and has pleura streaks; the notum area is mostly dark brown with
germinate medial stripe, the stigma stain on the forewing of
canadense is paler.
(Stenacron interpunctatum / canadense)
(Stenacron interpunctatum / ohioense)
These two forms are confused because of historical taxonomic
issues. Canadense from an historical profile aspect does not
have spiracular spots on the sides of the abdomen but ohioense
does. Herman T Spieth in 1947 synonymized ohioense with
canadense and wrote a new description for canadense which
included ohioense and spiracular spots.
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Features commonly shared in the two are;
Both have a line on the frontal shelf that is most often not
connected under the antenna bases going from compound eye to
compound eye, black spots on the vertex of the head, large black
oblique pronotum streaks with germinate medial stripe.
Notum is striped and very dark with a black scutellum; both also
have pleural streaks with prominent dorsal median stripe on
tergites 1-9 with heavy blackish shading in the sublateral and
transverse banding areas. The stigma stain in the apex of the
forewing wraps over the apex both.
Defining features to separate are;
Size is the biggest factor, ohioense male is 9 mm and the female
is 11 mm. In canadense the male is typically 10 mm and the
female is 13 mm, ohioense commonly has reddish shading in the
lateral areas of the notum, and canadense is tawny brownish
yellow, ohioense has large spiracular spots and canadense has
black shading in the spiracle area, but no spiracular spots
present.
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(Stenacron interpunctatum / ohioense)
(Stenacron interpunctatum / frontale)
These two are very likely to be confused in both male and
females. There are geological variations of both forms. To date
there are 2 geological variations of ohioense and 2 for
frontale. The lightest of the ohioense matches the standard form
of frontale and can only be separated by genital comparisons.
However they can be separated superficially by a couple
features.
Features commonly shared in the two are;
Black marks on face and top of the head, black oblique streak on
the lateral area of the pronotum, dark notum with germinate
medial stripe, pleura streaks, germinate dorsal median stripe on
tergites 1-9, sublateral tergite shading, with spiracular spots.
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Defining features to separate are;
Frontale has a median crania spot and dashes below the antenna
bases, ohioense has a frontal shelf line that is very near
complete from compound eye to compound eye, with a median dark
area on the pronotum, ohioense has a dark triangle shaped spot
in front of the forewing root and frontale does not, frontale
has a brownish notum with yellowish lateral shading and in
ohioense the lateral shading is most often reddish.
The background colors of all tergites in frontale are yellowishcream and ohioense is commonly hyaline with slight yellow-green
tinge. The tails of frontale are whitish with reddish-brown
articulations;
in
ohioense
they
are
yellowish
with
no
articulations.
(Stenacron interpunctatum / proximum)
(Stenacron interpunctatum / conjunctum)
These two forms are so close that they are very difficult to
separate. But they can be separated by genitals and very fine
defining features. As well as seasonal variation there are 2
types for the conjunctum form the darker variation looking very
much like proximum and the lighter variation looking very much
like majus.
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Features commonly shared in the two are;
Black marks on face and vertex of head, oblique pronotum
streaks, pleural streaks, germinate dorsal medial stripe on
abdomen, small diffused spiracular spots.
Defining features to separate are;
Conjunctum has a midcrania spot and proximum does not, on
conjunctum the stigma stain goes over the apex of the forewing
and this does not occur in proximum. The germinate dorsal stripe
on the abdomen of proximum is present on tergites 1-8 and is
present on tergites 1-5 on conjunctum. The tails on proximum are
yellowish without any articulations, and on conjunctum the tails
are whitish with articulations.
The genitals of both differ by the type and size of the spines.
Conjunctum only has a lateral cluster of spines with minute
spines covering the apical portion of each lobe. In the apical
portion on proximum these spines are stouter and the lateral
cluster has independent sublateral spines. However both have
terminal, lateral cluster, and median apical spines.
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(Stenacron interpunctatum / majus)
(Stenacron interpunctatum / conjunctum)
Currently there are 2 geological variations of the form
conjunctum and 2 variations for the form majus. Both are very
similar to each other but can be separated by the fine detailed
features and genitals of the males.
Features commonly shared in the two are;
Both have a median crania spot, dashes below antenna bases,
small black spots at the corners of the compound eyes, small
reddish spot at the cranium suture on the vertex, with black
spots on either side of the vertex, posterior edge shaded
blackish. Both have pronotum lateral streaks, darker brownish
notum, pleural streaks are present; germinate median line on
tergites 1-5 with black spiracular spots. Both have white tails
with articulations.
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Defining features to separate are;
Overall size majus is slightly larger than conjunctum, majus has
median crania shading and a slight hyaline frontal shelf. Most
of the upper area of the head in conjunctum is brownish and in
majus it is only slight orangey shading. Majus has black ringed
ocelli and conjunctum does not have this feature as in true
interpunctatum Say. In majus on the notum there are sublateral
black streaks that conjunctum does not have, the scutellum of
majus is brownish tipped with yellow and on conjunctum it is
brown. The forewing root of majus is hyaline fleshy colored and
conjunctum is yellow. The germinate median line on the abdomen
of majus is a very fine grayish line restricted to the median
area of tergites 1-5 and the spiracular spot on majus are
prominent large and black.
(Stenacron candidum)
(Stenacron
minnetonka)
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Features commonly shared in the two are;
Both of these forms have a black spot at the median crania area,
black marks below antenna bases, small black spots at the corner
of the compound eyes, black spots on the vertex on either side
near the compound eyes. Both have lateral streaks on the
pronotum, brownish notum with a yellow scutellum, and no pleural
streaks. Both have a minor geminate median line restricted to
the posterior edge of each tergite, and black spiracular spots.
Defining features to separate are;
Size is very important when separating as minnetonka is large by
several millimeters. On candidum the dashes below the antenna
bases is in fact an elliptical spot and not a true dash as in
all others, minnetonka also has deep prominent orange shading on
the lateral areas of the notum above and forward of the forewing
root and one in front of the middle coxa. On minnetonka the
median spot on the rear femora is absent on most samples and
this spot is present on candidum. The spiracular spots on
candidum are aslant meaning elongated and on an angle and they
are small and round on minnetonka. The tails are also different
on minnetonka they are very pale yellow with articulations, and
on candidum they are white without articulations.
(Stenacron interpunctatum / heterotarsale)
(Stenacron interpunctatum / affine)
Doctor Traver synonymized these two in 1935. We can surmise that
they are synonyms and are very likely geological and or
sessional variations of each other. However based on very fine
difference we can separate them. Because there is so much in
common we will only discuss the defining features to separate
them.
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Defining features to separate are;
The principle features are the size affine is smaller than
heterotarsale, affine has pinkish shading on the lateral areas
of the notum and on the pleura, heterotarsale commonly but not
always has a brownish triangle stain above and forward of the
forewing root.
The abdomen of affine is stated as being hyaline, and
heterotarsale has a pale creamy-yellow abdomen. In the tails of
affine the tails are white without articulations and the tails
of heterotarsale are hyaline with articulations.
Dr Traver also noted the genitals of affine differ slightly from
the coastal plain variation being heterotarsale.
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(Stenacron interpunctatum) Say 1839
(Stenacron floridense)
In this selection we will compare the true interpunctatum (Say)
1839 to a newer less known species floridense Lewis (1974).
Features commonly shared in the two are;
Both have black ringed ocelli with spots on the vertex, pale
hyaline pronotum with fine black oblique lateral streaks, both
having brownish shading in two areas below the forewing root,
yellowish-white scutellum, stigma stain going over the apex of
the forewing, hyaline abdomen with fine blackish transverse
bands.
Defining features to separate are;
True interpunctatum Say has black marks on the face and
floridense does not. Note; according to Lewis (1974) floridense
may have marks on the face; if so typically very faint or almost
nonexistent. The head of interpunctatum Say is very bright green
throughout the entire head, whereas floridense is very pale
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yellow. Floridense has a distinct red triangle stain on the
vertex and interpunctatum Say does not. The median area of the
notum on interpunctatum Say is typically very dark brown with
lateral reddish-orange shading. The notum on floridense is pale
clay-brown colored with fleshy-yellow-pink lateral areas. The
transverse bands on true interpunctatum Say have a blackish
rectangle in the median area of each tergite and this does not
occur in floridense. The genitals of floridense are very
distinct an not likely to be confused with any other in the
genus. Floridense has 1-3 very large dorsal axial spines.
(Stenacron carolina)
(Stenacron pallidum)
Features commonly shared in the two are;
Both of these species have black marks of the face and vertex of
the head, oblique pronotum streaks at the lateral areas of their
pronotum, no pleura streaks present, stigma stain going the apex
of the forewing, blackish tergite transverse bands, and no
spiracular spots.
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Defining features to separate are;
The compound eyes spacing in carolina is unlike any other in the
genus. The eye spread is typically 1.5 X the width of the
compound eye itself. In descriptions the eye spacing is commonly
referred to as being remote. Size is the biggest facture
carolina is most typically seen as 10 mm and the male pallidum
is 7.5 mm. Carolina is very bright yellow throughout and
pallidum is more of a tawny color with a hyaline abdomen.
The transverse banding of carolina is also like no others in the
genus it bands wrap the ventral side of the abdomen as gray
shading. Pallidum also has wide purplish-black transverse
banding. The tails of carolina are dark smoky gray without
articulations and pallidum has hyaline tails that are also
unarticulated.
(Stenacron interpunctatum / areion)
(Stenacron interpunctatum / affine)
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Features commonly shared in the two are;
Both of these are very pale and very similar in size, spots on
the vertex of the head, no pleura streaks, stigma stain going
over the apex of the forewing, hyaline white abdomens without
spiracular spots, and hyaline-white tails without articulations.
Defining features to separate are;
Areion has black dashes below the antenna bases and affine may
have very faint grayish markings. There are black oblique
pronotum streaks on areion and these are absent on affine. The
scutellum on areion is bright yellowish-white, and on affine it
is medium brownish-yellow. The entire notum of areion is deep
tawny orange with brighter lateral edges, and on affine it is a
very pale tawny color with pinkish lateral areas. The transverse
tergal bandings on areion are brownish with tawny orange
transverse shading on each tergite, and on affine they are very
fine blackish shaded with a somewhat metallic look.
(Stenacron pallidum)
(Stenacron interpunctatum / heterotarsale)
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Defining features to separate are;
Size is the biggest facture is heterotarsale is 9 mm and
pallidum is 7 mm. Pallidum has black marks on the face and
heterotarsale only has small black spots at the corners of the
compound eyes and pallidum has dashes bellow the antenna bases.
There are pronotum streaks on the lateral areas of pallidum and
heterotarsale is void of any pronotum markings. The abdomen on
pallidum is hyaline white and on heterotarsale it is creamyyellow. The tails of pallidum are hyaline without articulations,
and on heterotarsale they are hyaline with articulations.
Male Adults Lateral views
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Female’s Lateral views
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Male Abdomens lateral View
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Master dorsal notum and Pleura Views
gildersleevei
canadense
ohioense
frontale
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proximum
majus
conjunctum
minnetonka
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candidum
pallidum
carolina
areion
330
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affine
floridense
heterotarsale
interpunctatum
Say
331
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gildersleevei
ohioense
canadense
frontale
proximum
conjunctum
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majus
minnetonka
candidum
carolina
pallidum
areion
333
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affine
floridense
heterotarsale
interpunctatum
Say
334
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Male heads anterior View
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Forewings
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Adult Couplets
Note: All past authors on all species indicate variation in
maculation from holotypes, Paratypes, and haplotypes as to their
species concepts. Some samples missing maculation some having it
when it shouldn’t be there. Line up your sample to the nearest
form keeping the geology of the substrate in mind, then lookup
current species status by the form name.
The strongest maculation on Stenacron are; spots below antenna
bases, Black ringed ocelli, black spots on top of head, pronotum
streaks, pleura streaks, stigma stain over apex of forewing, and
spiracular spots.
Secondary maculation markings; spots and shading
crania center structure of clypeus margin, median
notum and pronotum, spots in the R1&R2 interspaces,
shading on tergites, median abdomen stripe, transverse
on median
stripe on
transverse
bands.
Fore tarsal ratios can be helpful but often are all over the map
in size. Reading Spieth 1947 will give you insight into that.
It’s not useless it is just not to be trusted that much.
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1. affine; head pale yellow only small black spots near the
compound eyes on clypeus, small black spots on vertex with
reddish spot at cranium suture, no pronotum streaks, no pleura
streaks, stigma stain over apex of forewing unknown, tawny
notum with pinkish tinge, narrow purple-black transverse
bands, with no spiracular spots.
2. areion; small spots under antenna bases, small black spot
near compound eyes on the clypeus, orange vertex with black
spots on either side, pronotum marked with fine black streaks,
mars orange notum brighter on the sides with red-brown shading
on parapsides, scutellum yellow in the center, no pleura
streaks, stigma stain over apex is unknown, white abdomen with
or without mars orange-brownish transverse bands.
3. canadense; clypeus yellow-hyaline, median crania spots,
blacks spots below antenna bases, small black spots corner of
compound eyes, black ringed ocelli, brown vertex with blackish
triangle in median area with two small black spot, pronotum
large black lateral streaks, black triangle spots in front and
above forewing roots on the lateral side of notum, deep
brownish-black notum, scutellum black, strong pleura streaks,
stigma stain going over the apex of the forewing, heavy black
shading on at tergites lateral and median, with submedial pale
spots, no spiracular spots.
4. candidum; yellowish head vertex sight orangey toned, clypeus
median crania spot, elliptical black spot below antenna bases,
small black spots at the corners of the compound eyes, ocelli
not black ringed, brownish triangle on vertex with small black
spots, posterior edge grayish, pronotum, with lateral streaks,
notum brown, no pleura streaks, stigma stain not over apex of
forewing, yellow abdomen, black transverse bands pointed in
the median area of each tergite, prominent can be aslant
spiracular spots.
5. carolina; compound eyes wide spread, clypeus small spot at
the corners of the compound eyes, vertex two grayish black
sots brownish shading, pronotum with very fine lateral
streaks, pleura bright yellow no pleura streaks, stigma stain
over the apex of the forewing, tergites with black transverse
bands wrapping the sternum as faint gray bands.
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6. conjunctum; clypeus pale yellow with a midcrania spot, a long
fine dash below antenna bases, moderately sized black streak
at the corner of the compound eyes, ocelli not black ringed
but heavily shaded in brownish orange, red spot at the palmen
body, median black triangle spot, with two small black spots,
pronotum with moderate black lateral streaks, pleura streaks
present, stigma stain going over the apex of forewing,
germinant median stripe on tergites 1-4 some 1-5, black
transverse band with heavy brown transverse shading, small
defused spiracular spots.
7. floridense; head pale yellow with small black spot at the
corner of compound eyes, faint gray spots rarely on face,
distinct reddish spot on vertex with two small black spots,
ocelli black ringed, pronotum hyaline with lateral fine black
streaks, notum dark chocolate brown, mesoscutellum whitishcream, no pleura streaks, stigma stain over the apex of the
forewing likely, very fine blackish transverse bands.
8. frontale; hyaline-yellow clypeus, prominent median crania
spot with shading, black dash’s below antenna bases, larger
black streaks at the corners of the compound eyes, green below
ocelli, ocelli black ringed, brown around lateral ocelli,
vertex yellowish with brown-black triangle spot with two small
blackish spots, pronotum yellow with prominent lateral black
spots, pleura streaks present, faint germinant median notum
stripe with yellow scutellum, stigma stain not over apex of
forewing, abdomen with median stripe on all tergites, with
pale submedial spots, heavy brownish transverse shading, with
black transverse bands, large infused prominent spiracular
spots.
9. gildersleevei; clypeus yellow turning green, transverse black
band across face from compound eye to compound eye forming a
complete smile, some males have a broken band, brownish around
all ocelli, palmen body red spot, medial black triangle on
vertex with two small spots, pronotum yellow with median black
stripe, and lateral black spots, scutellum brown tipped with
black, remaining notum deep tawny-brown, with large blackish
triangles in front and above forewing roots, no pleura streaks
all coxa with blackish marking, abdomen solid black median
stripe on all tergites, with sublateral pale spots that are
thin and not touching the anterior or posterior for all
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tergites, black sublateral shading with prominent spiracular
spots separated from sublateral shading.
10. heterotarsale; faint yellow hyaline clypeus with a light
gray margin, small black spots at the corner of the compound
eyes, brighter yellow around ocelli, ocelli not black ringed,
brownish triangle stain on vertex with black spots on each
side, posterior margin smoky, pronotum yellowish without any
makings, notum largely brown, scutellum tipped with ocher
yellowish, tawny pale yellow notum lateral sides, pleura
yellowish some samples not all have a pale brownish streak on
the pleura anterior to the forewing roots, slight deeper
brown-orange right in front of mid-coxa, stigma stain going
over the apex of the forewing, black transverse bands on all
tergites, with no spiracular spots,
11. True interpunctatum Say 1839;
Head bright yellow turning bright green on vertex, many
sample may have a median crania spot, all samples will have
black dash’s under the antenna bases, with small black spots
near compound eyes, antenna usually black not gray, ocelli
prominently black ringed at the bases, vertex with a pair of
black spot, some samples black triangle spot, pronotum
hyaline yellow tinged at lateral areas with fine lateral
stripes, dark chocolate notum, scutellum yellow or yellow
tipped, pleura yellow-tawny with slight orange cast in front
of mid-coxa, coastal margin of forewing generally completely
black tinged, all longitudinal veins yellow at base turning
yellow-green-black as they enter the stigma stain, stigma
stain greenish-amber going over apex, commonly with strong
intercalaries in the right wing, abdomen hyaline, black
transverse bands with an median posterial spot on the band
often shaped like a rectangle, no spiracular spots.
12. majus; head pale yellow green clypeus grayish, black lines
below antenna bases, small spots at the corner of the compound
eyes, slight orange shading forward of cranium suture, red
spot palmen body, black ringed ocelli, small black spots on
either side of the vertex, pale grayish posterior edge,
pronotum yellow with slight median spots having lateral
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streaks, notum largely reddish brown in the meson area paler
at lateral areas, commonly very fine black stripes in front
and above forewing roots, scutellum brownish tipped with
yellow, lateral areas of scutellum tannish with dark gray
staining in post scutellum areas, pleura bubble gum pinkorange with brown over tones, pleura streaks, with coxa
markings, forewings stigma stain going over the apex of the
wing, abdomen, often a faint gray very fine medial line on
tergites 1-4 or 1-5, black transverse bands with a metallic
silvery gray shading, often very large spiracular spots, large
than everything in the genus.
13. minnetonka; pale yellow clypeus with mid crania spot, long
thin dash’s below antenna bases, small black spots corners of
the compound eyes, slight orange shading between antenna bases
and lateral ocelli, ocelli black ringed, ocelli to the rear of
vertex chocolate brown, two small black spots on vertex, with
blackish posterior margin some samples having a blackish
medial triangle spot, pronotum largely hyaline slight yellow
on the lateral areas, with lateral black streaks, notum
reddish-orange, brownish germinant medial stripe dark near
scutellum, scutellum yellow with pale lateral areas, lateral
areas of notum tawny with orange tones, pleura unmarked
yellowish-brown with slight orange area in front of mi-coxa,
stigma stain is unclear but likely over the apex, abdomen with
clearly black transverse bands with elevation in median area
of each tergite somewhat forming a arrow pointing forward,
small but prominent spiracular spots.
14. ohioense;
clypeus yellow green with a black line going for
compound eye to compound eye forming what looks like a
complete smile not always complete, orangey-brown around
antenna bases, from ocelli back brownish red, ocelli black
ringed, black spots on vertex with median triangle black
stain, posterior margin black, pronotum deep yellow with
strong black median line with reddish surrounds lateral black
spots large often connected to posterior edge, notum largely
deep reddish-brown, with germinant medial stripe on transverse
suture, dark brown spots forward and above forewings, pleura
largely yellow with fore-coxa spots, pleura streaks, forewings
stigma stain going over the apex, abdomen largely blackish or
infuscated gray shading, having a strong medial stripe, with
variable submedial pale spots, with infuscated sublateral
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areas, heavy transverse dark shading with black transverse
lines on all tergites, large spiracular spots, in fused with
lateral area of tergite transverse shading.
15. pallidum; clypeus very pale yellow very pale or absent
median crania spot, fine dash’s below antenna bases, small
black spots in the corners of the compound eyes, brighter
green-yellow from antenna bases to posterior margin, black
spots on vertex, red spot at palmen body, pronotum pale
yellow-hyaline with fine black streaks near lateral edges,
notum pale tawny-amber-yellow with paler lateral areas,
scutellum yellowish with tan sides, pleura no streaks with
pale tawny yellow all over, stigma stain based on sample in
photo plate stain likely over apex, abdomen moderately wide
purple-black transverse bandings, without spiracular spots.
16. proximum; clypeus very pale yellow-hyaline, dark medial
shading on the frontal margin, with pale median crania spot,
small black dash’s below the antenna bases, small black dah’s
at the corner of the compound eyes, ocelli not black ringed
but ringed with brownish-red shading, red spot at palmen body,
two very small black spots on vertex, with posterior margin
brownish-red shading, pronotum hyaline-yellow with lateral
black streaks, notum in the median area deep brown darker near
scutellum, scutellum yellow with a touch of green, pale yellow
tan lateral areas, pleura medium yellow with areas of orangeybrown with pleura streaks, forewing stigma stain not over
apex, germinant medial stripe 1-7, with germinant submedial
shading on 1-4, black transverse bans with forward transverse
shading, moderate spiracular spots infused with transverse
bands.
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Adult Male Full Descriptions
All descriptions are free of synonym forms, based on original
descriptions, and reared samples that align with the proper
original historical profiles. Every attempt was made to base our
descriptions on the original description combined with other
matching ones with reared samples from Southern Ontario that
meet the criteria of the original descriptions. If new
information can make a concept more concise we are commenting in
a manner that is easily recognized with parenthesis. We will not
write a description that was affected by a synonym. These are as
original and as clear as historical documentation and current
information can allow. Pure clarity to original form combined
with new study information clearly indicates all the original
concepts. All are listed in their form names, not species.
affine
Traver 1933
Synonymized to heterotarsale 1935
Notes; Based on Travers description and our illustration facsimiles. To the
best of our knowledge affine has never been seen outside the Cornell
collection and was never reviewed, not even for DNA according to Jeff Webb.
This description follows Traver 1933 very close. (However from our full
genus morphology studies, altitude, and ecology affect it can be
clarified).
Body size; 7-8 ♂ mm, 9 ♀ mm
Forewing size; 8-9 ♂ mm
Tails; 18 ♂ mm
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Head; Pale yellowish with very pale clypeus (likely almost
hyaline). Two very small dark dots by the corners of the
compound eyes on the lateral areas of the clypeus. Traver does
not remark that the ocelli are black ringed at the base as in
true interpunctatum Say. Traver remarks very small red spot in
the area of the cranium suture at the palmen body. On the vertex
of the head two very small black spots, the posterior margin may
be slightly dusky.
Pronotum;
As in all the pale forms having a hyaline pronotum that is
unmarked as in heterotarsale may have slight yellowish tinge at
the lateral areas.
Notum; entirely pale yellow with tinge of pink without any dark
markings, some structures of the notum and pleura very narrowly
darker. (Likely darkening tones typical to the genus in the
scutellum area).
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Pleura; very pale whitish-yellow with a slightly brighter
yellowish area in front of middle leg as all forms in the genus
have, (may be even slightly orange).
Forelegs; faintly tinged in pale yellow with an apical and
median femora bands. (Tarsi and tibia would likely be hyaline
with smoky-brown tipping’s). Traver never included a fore tarsal
ratio, if truly like heterotarsale about ½ the length of the
second.
Middle and rear legs; (would be hyaline with very faint femora
bands), Traver comments both legs are missing median bands, and
apical spot is very faint.
Forewing; because Traver synonymized affine to heterotarsale in
1935 as per Dr Needham, and her notes showing a very close
resemblance, we are using a heterotarsale forewing here. This is
a female forewing so there are more crossveins than in a male.
We can also surmise that like as in most in the genus, and like
heterotarsale, that the stigma stain in the apex of the forewing
wraps over the apex, (we suspect a very pale stigma stain much
lighter than heterotarsale).
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Hindwing; again using heterotarsale the hindwing is likely very
pale yellow in the basal area, and apical margin with very fine
faint brownish shading.
Abdomen; semi-hyaline or yellow-cream throughout with narrowly
purplish-black transverse banding on tergites 1-9 (that would
stop short of the spiracles) with no spiracular spots, posterior
of 8th tergite narrowly tinged in yellow, 9th – 10th pale yellow
(likely having a faint slight brownish-red stain) at the
posterior area of tergite 9.
Tails; whitish at the basal area turning very faintly smoky
without articulations.
Genitals; Traver 1933 “differ but just slightly from coastal
plain species” meaning heterotarsale: Based on her comment we
suspect this is the difference; samples likely lacked sublateral
basal spines from about 4-6 as in heterotarsale to about 1-4,
the general shape would still be blocky like in shape, and the
terminal spines likely pointed to the median posterial lobe,
more than to the middle like heterotarsale. What we just
explained is very common in Stenacron. Like changes to
mouthparts, environmental shifts do take place, and my statement
is based on affine actually being a true geological variant,
which we doubt. It also seems that the higher the altitude the
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fewer the lateral spines carolina has almost none only 4 minute
spines.
areion
Burks 1953
Synonymized to interpunctatum 1974
Original description modified
Notes; the greatest confusion was Burks stating “Bright” mars orange on the
crossbands of the tergites. If he had of said mars orange his species
concept would have made more sense. Both majus, and conjunctum can have
orangey-brown transverse bands in their lightest variations. If Spieth 1947
had not synonymized majus to interpunctatum, Lewis would likely have picked
the pale majus form, over the hybrid theory.
body size; 7 ♂ mm, 8-9 ♀ mm
Forewing size; 8 ♂ mm, 10 ♀ mm
Tails; 18 ♂ mm
Head; Face below antennal sockets light yellow, a small black
mark on margin of frontal shelf below each antenna base, each
antenna pedicel yellow, flagellum slightly grayed near base,
area of face between antennal sockets and lateral ocelli deep
yellow, vertex Mars orange. Burks does not state black ringed
ocelli.
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Pronotum; pale yellow, black streak on either side, mesonotum
amber-brown, with red-brown shading at posterior ends of outer
parapsides and on lateral margins anterior to forewing bases.
Mesoscutellum; yellow in the center, Mars orange at margins.
Mars orange shading also present on lateral margins of mesonotum
posterior to forewing bases.
Pleura; bright yellow, minute dark brown point on each middle
and hind coxa suture, thorax sternum bright yellow.
Forewings; hyaline, (It is very likely that Burks samples had
the same forewings of interpunctatum).
Stigmatic areas stained
with brown, veins light yellow-brown, crossveins black, two
crossveins below bulla connected by black dash, veins and
crossveins of each hindwing pale yellow, but crossveins and
intercalaries at outer margin black.
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Legs; deep yellow, median and apical dark brown crossbands
present, tibia pale yellow, apex black, tarsus white, apexes of
segments slightly darkened, first segment 55% as long as second
segment, middle and hind legs white, each femur with a faint,
dark brown shading in middle and a well-marked, brown band at
apex.
Abdomen; white, posterior margin of each tergite 1-7 with Mars
orange crossbands, spiracular dots absent, apical three tergites
yellow-orange, with overlying Mars orange shading.
Tails; white, articulations not darkened.
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canadense
Walker 1853
Notes; This description is based on many historical descriptions and
records. But, more so on reared samples from southern Ontario that key out
to this form in the larva exuvia and the adults of male and females.
Important notes; Spieth 1947 included ohioense in his new description for
canadense which
caused
great
taxonomic
confusion
in
understanding
canadense, in its true to form state. See taxonomic confusion for a clear
understanding between canadense and ohioense.
Body size; 8-9 ♂ mm, 13 ♀ mm
forewing size; 9 ♂ mm. 14 ♀ mm
Tails; 22-24 ♂ mm
Head; yellowish-hyaline on the clypeus, dark brownish-black on
the vertex. Frontal shelf slightly hyaline with median crania
spot large streaks under antenna bases extending to median spot,
larger spots near corners of compound eyes but not connected.
All these markings make the general appearance of a transverse
band across the face. In some of the darkest females these spots
can connect forming a complete smile. Vertex dark chocolate
brown some samples having very small black spots near the
compound eyes blackish at the posterior margin. Our Ontario
samples have black ringed ocelli.
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Pronotum; brownish-black in the median area with hyaline yellow
lateral edges, median stripe present with large lateral pronotum
spots connected to posterior margin and often adjoining the
median stripe.
Mesonotum; deep brown with triangle dark reddish-purple spots
anterior and lateral to the base of forewings, germinate median
line from anterior area to middle mesonotum region, scutellum
can be narrowly tipped with pale yellow but generally black.
Pleura; yellowish-golden background coloring with structural
areas darker reddish-brown, oblique and prominent purplish-brown
pleural streaks extending from wing roots to the sternum,
forecoxa with two brown spots per coxa.
Forelegs; fore femora deep greenish-yellow with prominent
brownish-purple apical and median bands on all femora, fore
tibia yellowish-brown with blackish-brown shading at the apex,
fore tarsi smoky yellow-whitish with the first segment being
about 40% of the length of the second. Mid and rear legs much
like forelegs but paler.
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Forewings; costal vein yellowish-gray, subcostal and R1&R2 veins
yellow in basil area turning brownish in apical area. Stigma
stain reddish-brown turning smoky-yellowish in the apex region
with stain extending over the apex of the wing. Crossveins dark
brown blackish in coastal areas, typically in the costa and
subcosta interspaces there are 4-6 aslant crossveins below the
bulla and 12-17 above the bulla. In the subcosta and R1
interspaces there are normally 3-6 crossveins below the bulla
and 8-12 from the bulla to the apex. In the R1&R2 interspaces
there are typically 2-3 crossveins that are commonly connected
by a black dash in the bulla area.
Hindwing; longitudinal veins in the basil area often yellow
turning hyaline in the apical area with the posterior edge being
dusky brown black terminal edge.
Abdomen; important note; canadense true to form does not have
spiracular spots but often has dark lateral markings that can
appear to be spots infused with the transverse bands. If your
sample looks like canadense but has spots see the ohioense
description. Background coloring most often yellow-hyalinewhitish, strong piceous coloring on all tergites occupying the
median and sublateral areas infused with wide transverse
banding. Median longitudinal stripe on all tergites with
submedial pale areas that form discontinuous stripes, wide
pronounced transverse bands on tergites 1-9 with an incomplete
paler band on the 10th. Background coloring of 8-10 orange-rustyclay terminating in yellowish-orange coloring on the 10th.
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Tails; whitish-yellow turning smoky at the apical ends, with
pale reddish-brown articulations.
Genitals; pale brown yellow similar to interpunctatum (Say) and
not like frontale, many samples having two sets of meson spines
with apical spines. Lateral spine cluster often like frontale
with more than 6 spines combined as one cluster, basil spines
are smaller more spread out but still as a group. In the basil
cluster there is often 1 spine coming around to the dorsal side.
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Candidum
Traver 1935
Notes; Based on Traver 1935, Burks 1953, Lewis 1974 and many reared and
collected samples from southern Ontario.
Body size; 7.5 ♂ mm, 9.5 ♀ mm
Forewing size; 8.5 ♂ mm, 10 ♀ mm
Tails; 18-22 ♂ mm
Head; yellow-orangey-brown, yellow on the frontal margin, dark
spot on the median crania, elliptical black spots below each
antenna base, small black spots in the corner of each compound
eye, slight orangey shading in the ocelli area, ocelli not black
ringed as in interpunctatum Say. Vertex largely yellow-brown
with a brownish triangle in the median area, with black spots on
either side of the triangle, posterior edge darkened.
Pronotum; creamy-yellowish with oblique black spots in the
lateral area, no median markings, no lateral shading, posterior
may have slight grayish shading.
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Notum; brownish-amber colored in the posterial central area,
slight reddish-tan shading in the median area, with surrounding
areas being pale tawny-yellow, scutellum bright yellow with
tannish areas surroundings in the metanotum.
Pleura; principally yellow-tawny without any markings other than
faint gray stain above rear coxa, slightly orangey just in front
the middle and hind legs. No pleura streaks, bright yellow forecoxa, sternum yellow.
Legs; fore femora deep bright yellow with apical and median
bands that are prominent, fore tarsal ratio 45-50% the length of
the second section. Middle leg pale yellowish with apical and
median bands lacking the hyaline of other pale species. Rear
femora pale yellow slight hyaline strong apical band, one slight
dark dash as a median band on dorsal side only.
Forewing; candidum is noted as typically only having 1 small
back spot in the R1&R2 interspaces see Lewis 1974 figure (152)
and sample below, when diagnosing all Stenacron it is most
advisable to utilize the right wing. All Stenacron we observed
have a deletion of pigment in the R1&R2 interspaces of the left
wing. So candidum samples may have no pigment in the left wing.
The stigma stain does not go over the apex of the forewing.
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Abdomen; background color yellowish-white, creamy on the ventral
side, transverse black tergite bandings on 2-9 having a slightly
metallic silvery sheen on the front of the bands. In the medial
area of each band there is an enlargement commonly in the shape
of a point facing forward. Prominent spiracular spot that can be
elongated and slightly aslant, 8-10 slight orangey-reddish
coloring.
Tails; entirely white
Genitals; boot shaped with 2-4 apical spines, no terminal spines
but 4-6 minute spines on lateral lobe, with 4-6 lateral minute
spines.
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carolina
Banks 1914
Notes; Defining features compound eyes very wide spread 1.5 X compound eye
size only form in genus with this feature, orange amber stigma stain over
wing apex, terga banding wrapping around the sternum as gray shading,
bright yellow overall, smoky gray tails.
Body size; 10 ♂ mm, 12 ♀ mm.
Forewing size; 10.5-11.5 ♂ mm,
Tails; variable 24-30 ♂ mm
12.5 ♀ mm.
Head; Deep bright ocher yellowish, no black dash below antenna
bases, small black spots at the corner of the compound eyes,
slight reddish-brown shading below and at the ocelli area.
Ocelli black ringed as in interpunctatum Say, cranium suture
shading reddish-brown, fine gray spots on vertex, posterior edge
slightly dusky hyaline.
Pronotum; in some samples the pronotum maybe be whitish in the
median area otherwise yellow throughout, with very fine black
sublateral streaks.
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Mesonotum; mango-orange-ocher without any markings, surrounding
areas pale-yellowish-creamy, scutellum pale yellow somewhat
bright. Notum of samples from darker substrates can be brownish
in the notum but much lighter that interpunctatum Say.
Pleura; bright ocher yellowish with large pale cream colored
areas at the root of both wings, these areas connecting to each
other in the median pleura region behind forward spiracle.
Legs; all femora yellowish with fore femora being darker that
the others. Apical and median bands present on all femora,
median band faded out on rear femora. Fore tarsal ratio, first
segment about 55-60% the size of the second segment so longer.
Forewing; NOTE; often a creamy-yellow tinge in the costasubcosta interspaces near the bulla region. Costa longitudinal
vein yellow smoky gray, subcosta and R1 veins bright yellow, all
others yellowish-gray-brown, in the interspaces between the
costa and subcosta veins there are 5-6 aslant crossveins below
the bulla, 2-3 in the bulla, 8-14 beyond to the wing tip. Most
samples in the R1&R2 interspaces in the bulla area have 2
crossveins connected by black dash.
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Rare samples may not have a dash and only 1 cross vein. Stigma
stain orangey yellow turning gray-yellow and going over the apex
of the wing, some samples have a greenish tinge to the stain.
Hindwing; similar to forewing with yellow then black shading on
the posterior edge.
Abdomen; NOTE; posterior edges of tergites are blackish grayish
and wrap around the sternum as sternum bandings. Ground coloring
hyaline-creamy with moderate transverse black terga banding from
1-9, 10th void of markings. These bands wrap around the abdomen
as gray shading. Lateral edges may be yellowish-gray in some
samples in the spiracular area. No spiracular spots, 8-10 bright
yellowish.
Sternum bandings
Tails; in some samples from dark substrates can have very long
and dark gray tails, others are hyaline smoky with dark gray
articulations.
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conjunctum
Traver 1935
Notes; this description is based on Traver (1935) and many reared and keyed
samples from our collection in southern Ontario. There are two geological
variations of this form, the most common one being mostly hyaline white in
the abdomen, the second one yellowish like heterotarsale.
Body; 8 ♂ mm, 10 ♀ mm.
Forewings; 9 ♂ mm, 11 ♀ mm.
Tails; 18-24 ♂ mm.
Head; yellow, black spot median crania region, black dash below
antenna rather long but not connected to either the midcrania
spot or spots in the corner of compound eyes, hyaline frontal
shelf, small black spot corner of the compound eyes, brownishred shading around ocelli, and not black ringed as in
interpunctatum (Say). Reddish-brown dark shading rear margin of
vertex, two very fine black spots behind lateral ocelli and one
small red-brown spot at the palmen body, often two submedial
longitudinal pale yellowish streaks on either side in between
the black spots.
Pronotum; pale white-hyaline-yellow, oblique black streaks in
sublateral areas with very faint median blackish spot.
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Mesonotum; dark brown in median area, geminate medial stripe
paler in the median area of the thoracic notum, lateral areas
paler yellow-orange, scutellum brownish with paler tawny areas
anterior-lateral to it very pale samples may have slight yellow
tinge to scutellum.
Pleura; ocher yellowish with hyaline areas at the base of both
wings, oblique purplish-brown pleura streaks, sometimes with
brown spot on middle coxa, with pale yellow forecoxa.
Foreleg; femora ocher yellowish-green with median and apical
purplish-brown bands. Fore tibia paler in color blackish at
apex, fore tarsi approximately 40% on average the length of the
second. Middle and hind leg; like foreleg put much paler overall
hind leg having a fainter median band.
Forewing; costal and subcostal longitudinal veins yellow-brown,
all crossveins brownish-black, typically 2 crossveins in the
bulla area that have blackish pigment connecting them, 7-10
crossveins from bulla stain to wing tip in the R1&R2 space.
Stigma stain moderately pale reddish-brown-yellow wrapping over
the apex of the wing and most often having 1 intercalary spots
at the tip between the R1&R2. Hindwing; dusky brown shaded
posterior margin.
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Abdomen; terga 1-8 semi-hyaline white, some samples can be
almost yellowish in their ground coloring, tergites posterior
margins brown, slight black transverse bands. (Important notes)
germinate median line starting at the anterior median area of
tergites 1-4 or 1-5, these lines often not touching the
posterior edge of the terga. Some samples having pale anterior
sublateral gray shading on 1-4 as in proximum. 8-10 opaque dark
red, brownish over rusty-orange with the (terminal end of the
10th yellowish). Spiracular dots small defused hard to define not
like frontale, and very faint on tergites 3-7, slight gray-brown
sublateral shading infusing the dots but not connected. Medial
and lateral faint grayish-brown shading on tergites 4-7.
Tails; Whitish-hyaline with brownish-red articulations.
floridense
Lewis 1974
Original description Lewis 1974
Notes: as with all forms and species in the genus reported range is
questionable since being able to tell the difference on site can be
difficult with many forms. In this book we are showing in the photos plates
one larva and one adult female that align with this species from Tennessee
near the Kentucky boarder. Reading both Lewis 1974 A,B, descriptions which
appear to be the same description, it is clear that size is a issue. He has
larva size 8-10 mm, and male imago 7-9 mm? We can rule out confusion with
interpunctatum as floridense has 1-4 curved stout dorsal axial spines and
no others in the genus have axial spines. We can rule out larva confusion
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as floridense tergite maculation is very distinct.
The base line would
likely be 8 mm for the male, 10 mm for the female. It is unfortunate that
the samples at Bold Systems Museum larva photographed by Jeff Webb can’t be
used to clear this up. They are only in and around the 15-18 instars and
are not full grown. From our studies and Ide 1935 Stenacron larva reach
full body length at the 22nd instars when the wingpad reaches the posterior
edge of the 2nd tergite, then the wingpad rapidly grows till it almost
reach’s the posterior edge of the 4th tergite by the 24th instars. We have
also consulted The Mayflies of Florida and size is not covered.
Body size; 8 mm ♂, 10 mm ♀
Forewing; 9 mm ♂, 11-12 ♀
Tails;
15-22 mm
Head; clypeus pale yellow (likely having slight hyaline in the
median area), some samples pale grayish stains on the clypeus
but not like others; (not having dash’s below antenna bases or
black spot at median crania), deeper yellow with a cast of green
from ocelli to posterior areas, ocelli black ringed as in
median
stain,
interpunctatum
Say,
vertex
reddish-brown
(vertex stains are elongated in this genus unless it is a palmen
body spot), black or gray spots on either side of the cranium
suture slight brownish black shading at the posterior margin.
Pronotum; ligth yellow (likely hyaline in median area) with a
black streaks in the lateral areas.
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Mesonotum;
light
yellow
brown,
scutellum
and
surronding
whiteish, (slight darkening lateral to scutellum common to the
genus) yellow-tan laterally.
Pleura; pale yellow with slight amber area in front of middle
leg forewing roots (likely pale hyaline).
Forelegs; greenish-yellow with median and apical brown-black
bands, fore tarsal ratio is 2.0-2.4; or the first segment being
40-45% the length of the second, middle and hind legs pale
whitish both with apical bands, the middle leg has a median spot
the rear femora median spot is absent.
Forewings; forewing information is sparse, (based on the high
possibility of new sightings in TN we will use illustrated wings
from that sample as they would likely accurately reflect this
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species). Lewis states black dash present with 2 or 3 crossveins
in the bulla, stigma stain likely going over apex as most do in
the genus. Hindwings with darkened apical margin.
Abdomen; hyaline with faint black posterior margins that end
above the spiracles, no spiracular spots, dorsal area of
tergites 8-10 alabaster white, (likely a fine touch of very pale
yellow).
Tails; light gray throughout without articulations.
Genitals; very distinct from the entire genus; having large
later spines, 2-4 stout dorsal axial spines, (no others in the
genus has axial spines), with terminal spines, apical spine may
be present but often without.
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frontale
Banks 1910
Synonymized to interpunctatum 1947
Notes; this is based on Banks 1910, Traver 1935, Burks 1953, and reared
samples from southern Ontario that match this historic profile. There are
currently two geological types a dark type and a light type. The dark type
more aligns with the historical profile so this description is a historical
composition of the dark type.
Body size; 9 ♂ mm, 11 ♀ mm
Forewing; 10 ♂ mm, 13 ♀ mm
Tails; 22-26 mm ♂
Head; very pale hyaline yellow at the frontal margin darkening
at celli, median crania spot and shading, black dashes below
antenna bases, with moderate spots at the corners of the
compound eyes, very dark samples may have an almost complete
line from compound eye to compound eye. Slight orange-brown
shading around the base of antenna scape, ocelli black ringed,
with deep brownish red around the ocelli, vertex principally
yellow brown two small black-brown spots posterior margin often
blackish.
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Pronotum; hyaline-yellow often with a median spot and having
lateral black streak like stains.
Notum; dark brown with tawny-yellow lateral areas with orange
casts, scutellum brownish most often tipped with yellow, lateral
scutellum dark brown, post scutellum tannish lateral areas can
be shaded in gray no median notum stripe orangey-yellow lateral
areas.
Pleura; forward area and coxa brighter yellow-brown, wing roots
hyaline-yellow, median coxa to rear area brownish-yellow, with
pronounced pleura streaks that are normal more brownish then
blackish, Brown stain at mid-coxa root, hyaline area between the
wing roots.
Legs; Fore femora ruddy yellow-brown-gray with median and apical
bands that are fainter than most forms in the genus, fore tarsal
ratio is the first segment is 50-55% the size of the second, so
just slightly larger. Median and hind legs yellow-hyaline-gray
with median and apical bands.
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Forewings; costal, subcostal, R1 veins yellow basil turning
brownish in the bulla area, generally 4 or less aslant black
crossveins in the costal-subcostal interspaces below the bulla,
2 at the bulla, 9-12 beyond, in the R1&R2 interspaces below the
bulla there are normally 3 crossveins typical samples will have
a black dash some only 3 spots as seen in illustration. Stigma
stain fairly prominent reddish-brown and not going over the apex
key to form. Hindwing if there is any yellow basely it will be
very faint, slight yellow brown, with the posterior margin
narrowly brown.
Abdomen; creamy-yellow background most samples have a median
stripe on all tergites, typical samples have a double median
line on tergites 1-6 but not always, Variable sized submedial
pale spots often very small from the 1-5, then continuously
getting larger till the 9th. Typical samples have moderately
prominent sublateral shading that connects to the transverse
bands, more prominent it segments 1-5 brown-black transverse
bands on all tergites, moderately prominent spiracular spots, 810th dorsally ruddy-clay-red.
Tails; pale white-yellowish with articulations
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gildersleevei
Traver 1935
Notes; based on Travers original description with male and female samples
from Bronte creek southern Ontario.
Body size; 10-11 ♂ mm, 13-14 ♀ mm
Forewing length; 10.5-11 ♂ mm, 14 ♀ mm
Tails; 24-28 ♂ mm
Head; (Very rare sample may have incomplete transverse line
across clypeus Traver 1935), clypeus pale yellow slight greenish
tinge transverse line from compound eye to compound eye often
looking like a complete smile, turning brownish in ocelli area,
ocelli not black ringed, vertex principle brownish-red with a
small red spot at the palmen body at cranium suture, larger
median blackish triangle stain pointing forward, with small
black spots on either side.
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Pronotum; largely yellow with distinct black median triangle
line pointing forward, with prominent black lateral streaks that
commonly connect to the posterior edge, the lateral and median
terminal edge blackish.
Notum; median notum area very dark brown slightly lighter
lateral areas, black median stripe from pronotum to tip of
scutellum, lateral areas of scutellum very dark if not black,
post-scutellum distinct median triangle outline with pale
lateral areas, forward of forewing roots, blackish triangle
stain like canadense, with orangey-yellow background.
Pleura; prominently yellow with an overcast of reddish-brown
staining, fore coxa brighter yellow, above fore coxa on
[pronotum-pleura] dark blackish streak, fore coxa may have small
dark spot, black spots on either side of the middle and hind
coxa, on in front of middle leg often extending to breathing
spiracle, rarely but can have black spot at the top of the rear
wing root, wing roots hyaline-yellow.
Legs; fore femora deep yellow with orangey-brown cast, with
median and apical band very dark and prominent, tarsi tinged
with smoke stain fore tarsi ratio first segment 45% the length
of the second, middle and hind legs yellow-hyaline, with median
and apical bands often median band on hind femora paler.
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Forewings; (some sample may have milky tinge in the costal and
subcostal interspaces from the bulla area to the tip) Costal,
subcostal, and R1 bright yellow with a touch of brown, in the
costal-subcostal interspace normally 4-6 crossveins from costal
brace to bulla, 2-3 in the bulla, 12-15 beyond, Stigma stain
brighter yellow slightly ruddy and going over the apex of the
wing, R1&R2 interspaces at the bulla 3 crossveins connected by
customary black dash, other crossveins brownish black. Hindwings
very pale yellow at the base hyaline throughout with slight
brown stain at the apex and posterior areas.
Abdomen; background coloring can vary from yellow to creamy
whitish, typical samples are yellowish dorsally and whitish
ventrally, strong wide predominant median line from 1-9, reduced
to germinant medial stripe on the 10th, all tergites but 10th long
thin pale submedial spots almost forming a discontinuous
submedial stripe on either side of median line, very dark
sublateral shading nearly forming a lateral stripe with strong
spiracular spots often encapsulated with this shading, some
samples dark gray shading with spiracular spot sometimes making
them hard to see, parts of the 8th and 9th tergite ruddy dark red
clay coloring, 10th very dark reddish-clay coloring.
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Ventral; (The sample is a female making it orange) Both male and
female may have black markings near the posterial boarders, in
some cases as seen here forming the shape of a boat anchor, this
stains are not typically seen in the larva at any point in
development and they are not ganglionic created as far as we can
distinguish. This staining is for unknown reasons and does not
appear on all samples principally it has more to do with the
females.
Tails; yellowish at the bases turning dusky in the middle and
apical portions, with light brown articulations.
heterotarsale
McDunnough 1933
affine synonym 1935
Notes; this description was without the inclusion of affine. We believe
that Dr Traver felt it was too soon to make this synonym we find her
comments indicate this. This is based on McDunnough 1933, reared samples
from southern Ontario, and also Traver 1935 for details. Size greatly
impacted in the concept as affine was 2 mm smaller than true heterotarsale
from Burks 1953 forward.
Body size; 9 ♂ mm, 11 ♀ mm
Forewing length; 11 ♂ mm, 13 ♀ mm
Tails 22-26 ♂ mm
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Head; both the lower clypeus area and the posterior margin
hyaline slight gray shading posterior edge. Light yellow a
little deeper in the ocelli area, brighter on the vertex,
clypeus free of all black markings except tiny black dots at the
corner of the compound eyes, ocelli not black ringed as in true
interpunctatum Say, pale to dark brownish triangle stain
pointing forward in the cranium suture area on the vertex, small
to moderate blackish-gray spots on either side of this triangle
stain.
Pronotum; geological variation can shift pronotum to
but typical samples are pale yellow without any black
we have one female sample with very slight wanting
lateral marks but in our opinion should not qualify
markings, may have slight gray shading on posterior
median area but rarely.
Brown stain
hyaline,
marking,
of black
as black
edge in
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Notum; pale brownish in the median area turning yellow
laterally, scutellum yellow-ocher some with a touch of orange,
often pale faint gray staining lateral to scutellum, post
scutellum slight orangey-tan, in the forward area lateral near
forewing roots commonly but not always a brown stripe like
stain. This stain often absent on females.
Pleura; free of any markings yellow-ocher can be brighter yellow
in some samples, typical to the genus slightly orange-mango
coloring right in front of the middle coxa, forewing roots often
hyaline-yellow fore coxa brighter yellow.
Legs; fore femora deep yellow not too bright with slight cast of
brownish hues, median and apical bands brownish-purple fairly
prominent, tibia and tarsi hyaline with smoky tipping’s, for
tarsal ratio the first segment is about 45% the length of the
second segment, McDunnough states highly variable. Middle and
rear legs hyaline slight yellow with apical and median bands,
rear median bands faint may be reduced to fine line on dorsal
side.
Forewings; The sample below is a female so there are more
crossveins in the forward areas for the wing than in the male,
most males having longitudinal veins yellow in the basil area
turning brownish in the bulla region and continuing to the apex,
in the interspace of the costal vein and the subcostal veins
from the costal brace to the bulla area normally less than 6
black margined crossveins, 2 in the bulla area and 8-13 beyond
into the stigma area, in the R1&R2 interspace at the bulla there
are 2 or 3 crossveins black margined but not always connected to
for a black dash, left wing may only have 1 crossveins with a
larger black spot. Stigma stain ruddy yellow and going over the
apex of the wing. Hindwings pale yellow costal and subcostal
veins yellow with interspaces being pale yellow, posterior
margin pale yellow terminating with a very narrowly brownish
edge.
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Abdomen; typical samples are pale yellow, but hyaline- creamywhite samples are common, posterior margins of tergites 1-9 with
blackish transverse bands often ending short of the spiracle
area, no spiracular spots on any samples throughout history, can
have mild silvery metallic transverse shading in front of the
black bands, 8th on dorsal area slight infusion of ruddy-brownreddish-clay coloring, this coloring occupying the dorsal areas
of tergites 9-10, with the 10th terminating in yellow.
Tails; tails pale being whitish-yellow, males are more hyaline,
female are more yellow, all have very fine faint reddish-brown
articulations. In some samples tails are smoky very pale gray,
in this genus the substrate coloration and geology composition
has an enormous impact on color deviation from historical
profile.
Genitals; very blocky shaped but similar to interpunctatum Say.
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Ture interpunctatum Say 1839
Thomas Say
Free of synonym forms
Notes; to the memories of the Godfather of American Entomology Thomas Say
who died in 1834, this description is based on Say 1839, Walker 1853,
LeConte 1858, Hagen 1861, Walsh 1863, Banks 1910, Traver 1935, this also
included the reading of all flaveola notes and descriptions as it is a true
synonym of interpunctatum Say. Moreover from reared Ontario samples by us.
Before we start this is a great time to mention somethings. First Stenacron
did not start out with the name Stenacron. It started with the genus name
Baetis interpunctata. The genus name was changed to Heptagenia then
Stenonema, and then finally in 1974 the name Stenacron appears. Researching
this very old species is highly complex for many reasons. First is wording.
In 1853 new words were being used, by the 1880’s some of those words were
no longer in use. By 1900 we have word changes and about every 5 years new
words replaced old words till the 1980’s.
In order to dissect an old description too truly understands what was being
said required they usage of my very large 1912 dictionaries nearing 4000
pages. Every word ever written by that time was in these books. Reading
Needham 1905 for interpunctatum larva is very hard to read and understand.
There are some vintage documents that have been mentioned in many text that
are currently unavailable like Walsh 1862, some are in foreign languages
and we could not make use of them.
We have read every document availably that has any relativity to
interpunctatum to insure that this description is a modern but accurate to
original description. Ture interpunctatum is very distinct from every other
in the genus. We will put forth the most clarity possible including new
insight that clarifies old words and descriptions.
It is my honor and privilege on behalf of Thomas Say to resurrect and put
forth clarity to his species concept of Ture interpunctatum Say 1839
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Body size; 7.5 ♂ mm, 9 ♀ mm
Hagen 1861 8 ♂ mm
Fore wing size; 7.5-8.5 ♂ mm, 10 ♀ mm
Tails; 18-26 ♂ mm, Hagen 1861
(very district from all others by very a green head and black
antenna all in genus antenna grayish).
Head; very distinctly greenish throughout, clypeus pale yellow
can be almost hyaline at the lower frontal margin, not all but
often having a median crania spot, a clear black dash below each
antenna base, small black spot corners of the compound eyes,
from the lower scape or antenna bases to the posterior of the
head rapidly turning bright green, scape bright yellow-green,
pedicel bright yellow, flagellum or segmented part of antenna
blackish in most samples turning pale then terminating hyaline,
all others flagellum is gray, ocelli black ringed at the bases,
cranium suture is unmarked, a black spot of variable size on
each side of the vertex, uncommon but may have slight gray
shading at posterior margin of head.
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Pronotum; hyaline without any median marking,
pronotum black lines in the lateral areas.
crisp
clear
Notum; variability in notum intensity due to geological
pigmentation shifts. Most samples very deep chocolate brown in
the absolute center, getting paler as you move both forward and
backward as well as laterally, scutellum commonly yellowishwhite or just white, post scutellum peachy toned with darker
areas laterally, upper terminal lateral areas tawny-yellow
overcast with a mango tone, turning more yellow towards the
pronotum.
Pleura; yellow with a mango-brownish over tone but not
everywhere, forewing roots slight yellow or completely hyaline,
slight brown stain at the bottom of forward breathing spiracle,
with a mango tone in front of middle coxa, some sample have a
brown stain on the rear coxa, yellow sternum.
Legs; fore femora very distinct from all others in the genus,
strong bright green with a cast of yellow, powerful black
distinct apical and median bands, tibia rapidly shifting in
tones from deep yellow-green to almost hyaline, tarsi hyaline
all joints commonly tipped with smoky tinge, fore tarsal ratio
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the first segment is commonly 35-40% the length of the second,
middle and hind legs yellow-hyaline with median and apical
bands, some rear femora may have fainter median mark as to
geological conditions.
Forewings; without a doubt commonly very distinct by blackish
coloring. Costal, subcostal, and R1 veins yellowish at the costal
brace rapidly turning a blackish yellow all the way around the
posterior of the wing, all crossveins black, stigma stain
yellow-black slight cast of green going over the apex of the
forewing, interspaces between the costal and subcostal typical
samples less than 5 crossveins below the bulla 2 in the bulla,
and 9-11 beyond, R1&R2 interspaces typically 3 crossveins with
strong customary black dash, intercalaries often it the top of
right wing. Hindwings; costal and subcostal veins yellow-black
without any yellow staining in the membrane, posterior blackish
with intercalaries veins black.
Abdomen; white-hyaline some samples may have a faint creamyyellow background coloring, fine black tergite transverse bands
stopping short of the spiracle folds, these bands on 1-9 often
having a fine gray transverse shading, rarely sample may have a
median line in the 9th tergite or on the 1-5 tergites, this is
rare in both cases, the lines on 1-5 if present very fines gray
not black, median stripe in 9th sometimes arrow shaped pointing
forward see Lewis 1974 A Figure 122 for areion to see 9th median
line, in the median area of each transverse band there is
commonly a black █ rectangle shaped spot on tergites 1-7 larger
getting smaller as you move back to the 7th, 8th dorsally rustyorangey-brown some samples may have a cast of red, 9th and 10th
very similar with this opaque staining also commonly on the
ventral side, the terminal end and lateral sides of 10th pale
yellow.
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Rectangle spot
Tails; immaculate according to Say, pale whitish without any
form of articulation.
What an honor that was. Thomas Say died in 1834 it was 186 years
to bring his species concept back to its original condition.
majus
Traver 1935
Synonym of frontale 1947
Notes; majus has very distinct features that we believe are the reason the
Traver gave it species status. This description is based on Traver 1935 and
reared samples from Sothern Ontario. There are currently two distinct larva
types dark and light.
Body size; 9.5-10.5 ♂ mm, 12-13 ♀ mm,
Forewing size; 11 ♂ mm, 13 ♀ mm,
Tails; 24-28 ♂ mm,
♂ Average 10 mm
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Head; yellow throughout often rather bright, gray shading on the
frontal margin is common, median crania spot with shading, long
black dash below antenna bases, with small black spot at the
corners of the compound eyes, ocelli black ringed, slight
reddish-orange shading on forward vertex in front of the cranium
suture, red spot on the palmen body, small black spot on either
side of the vertex, with gray shading on the posterior margin.
Pronotum; largely pale yellow but often principally hyaline,
small blackish patch median posterior edge, with prominent black
streaks in the lateral areas.
Forward stripe
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Notum; from bubble-gum-mango to deep chocolate brown, becoming
paler in the lateral areas, most sample will have a distinct
forward notum stripe, scutellum yellow shaded in brown, post
scutellum tan median area with grayish staining on the lateral
areas, sometimes right behind rear wing roots.
Notum stripe
Often gray
staining
Pleura; yellow toward the sternum, often bubble-gum-yellowbrown, for coxa often bright yellow and marked with small brown
stains, brownish-black spots behind the middle and hind coxa,
forewing and rear wing roots often hyaline slight yellow,
prominent pleura streaks that are blackish-brown-purplish.
Legs; fore femora bright yellow slight cast for gray-brown with
strong prominent median and apical bands, hyaline-pale-yellow
tibia apically tipped with smoky gray, for tarsi hyaline with a
ratio of the first section being the same length as the second,
middle and hind legs, hyaline-white both having median and
apical bands.
Forewings; costal vein basally gray turning yellow in the bull
area till the tip, subcostal and R1 yellow basally yellow
turning brownish gray in the bulla returning to yellow to the
tip, crossveins in the interspaces of costal and subcostal veins
below the bulla, typical samples have 4 some samples 3 broad
black crossveins, 2 in the bulla area 9-11 above, left wing in
the R1&R2 interspaces in the bulla area, often one vein with
long spot, right wing 2-3 veins with a black elongated stain,
stigma stain yellow-brown going over the apex of the forewing,
intercalaries black at the tip on the right wing common.
Hindwing costal, subcostal, and R1 veins basely gray yellow
turning
yellow-hyaline,
membrane
in
the
posterial
area
yellowish, then tipped with brown then black staining.
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Abdomen; geographical variations in background coloring from
yellow-creamy to whitish-hyaline, strong black transverse bands
on tergites 1-9 the 10th unmarked, most samples will have silvery
metallic transverse shading in front of black bands, most
samples with have a broken germinant medial line that is very
fine gray on tergites 1-4, in some samples this line can go from
1-8, if it is pronounced it will only be on 1-4, prominent
spiracular spots, spots are highly variable in size, in females
the ay are commonly twice the size of the one pointed to, in
males often smaller abdomen below shows average spot sizes, spot
can be connected to the black transverse lines but not as a
rule, often having a cast of orangey-brown on the dorsal area of
tergite 7 this is rare in the genus, slight orangey-brown stain
in dorsal side at the posterior area of tergite 8, 9-10 fully
orangey-brown-rusty-clay colored.
Tails; pale- yellow-tan,
slight articulations.
narrowly
brown
at
the
joining’s
so
Genitals; as in frontale, however highly elevated in the median
apical area of each lobe but very blocky shaped like
heterotarsale.
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minnetonka
Daggy 1945
Notes; currently there are only two known complete descriptions of
minnetonka Daggy 1945, and Burks 1953. Although very similar they are also
different. Example Daggy 1945 indicates median crania spot, this is absent
in Burks. Daggy states rear wings distinctly margined, Burks distinct by
all veins been yellow. Burk was very descriptive on all of his
descriptions, actually over descriptive. This description is a combination
of both, combined with our morphology, and geological habit studies. There
are no known photos of this species. There is one sample we are presenting
in the photo plates that is highly suggestive of it and is within 200 miles
of holotype. Burk’s description includes new collections from Illinois.
This would describe differences likely caused be geological and dietary
morphology.
Body size; 9 ♂ mm, 11 ♀ mm,
Forewing length; 10 ♂ mm, 12 ♀ mm,
Tails; 24-28 ♂ mm,
Head; principally yellow samples may have a black median crania
spot, dashes below antenna bases, small black dots at the
corners of the compound eyes as all in the genus do, vertex
reddish-brown with small black spots on either side, blackish in
the median area and posterial margin, ocelli black ringed.
Pronotum; hyaline-yellow, may have sight brownish shading in the
median area, lateral black streak.
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Stenacron Larvae & Adults 2020
Notum; slight dark median line, most of notum reddish-brown
paler laterally like most in the genus, may or may not have
anterior-lateral black lines, scutellum yellow, with tan areas
surrounding.
Raised area
Pleura; largely yellow (likely slight cast of brownish) very
common to the genus, raised brownish red area between the fore
and mid coxa see above (also common to the genus) no other marks
notes by Daggy 1945, sternum yellow.
Legs; fore femora darker yellow with median and apical blackish
band, fore tarsal ratio is about 40% the length of the second
section. Middle femora with median and apical black bands, hind
femora median band absent apical present both median and hind
rather hyaline-yellow.
Forewings; (from Daggy, Burks and potential sample) like most in
this genus having yellow brown longitudinal veins, stigma stain
slight reddish-yellow, and going over apex as per Daggy,
customary black dash in bulla area. Hindwing Burks, all veins
yellow the membrane would also be yellow dusky brown posterior
edge.
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Abdomen; background color pale yellowish-hyaline posterior
margins of tergites 1-9 narrowly blackish, with pronounced
spiracular spots, tergites 8-10 dorsally infused with reddishbrown tergum 9 darkest, (Daggy v Burks) in the median area Burks
says black median tergite 1-8 with black cross line, meaning
median line, Daggy somewhat suffused with black dorsally,
meaning blackish transverse shading in the median area, sternum
white.
Transcribed; may have either median black
median black line could have either or both.
Tails; gray-yellow articulations brown
shading
or
slight
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ohioense
Traver 1935
Synonym free
Includes light and dark type
Notes; based on Traver 1935. There are currently two types for this form a
dark type and a light type. The dark type is the more commonly seen and
photographed, therefore this description is principally on the dark type,
but we will comment on variation of light types. Further information on
types can be found in the leopard larva changed its spots in the larva
book.
Body size; 9 ♂ mm, 11 ♀ mm.
Forewing size; 10 ♂ mm, 12-13 ♀ mm.
Tails; 22-26 ♂ mm.
Head; yellow turning brownish-red, clypeus yellow with a strong
black band going for compound eye to compound eye forming a
complete smile, rarely line is broken in the median crania area
and near the compound eyes, face turning orangey-brown between
the antenna bases and ocelli, ocelli black ringed at the bases,
vertex reddish-brown, black spots lateral of cranium suture,
median black triangle stain pointing forward and connected to
the posterior margin.
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Stenacron Larvae & Adults 2020
Pronotum; in the median area reddish-brown staining with
blackish median stripe, laterally yellow with predominant black
lateral stripes.
Triangle stain
Triangle stain outline
Notum;
Largely
reddish-brown,
pronounced
median
blackish
germinant medial stipe, stripe can be just purplish, often
reddish above forewing roots anterior-lateral of notum often
with black or very dark chocolate brown triangle stains in this
area see above, scutellum black lateral to that very dark or
black, post scutellum often a black triangle outline in median
area see above, light types can be very bubble-gum brown in the
notum area.
Pleura; yellow with orangey-brown casting, typical samples have
middle and rear coxa spots, prominent pleura streaks that are
very dark but not always blackish-purple, fore coxa brighter
yellow with dorsal coxa brown stain, common samples have a brown
or black triangle stain right behind the pronotum near forewing
roots see below.
Brown-black triangle stain
Legs; most sample all yellow, fore femora very deep yellowgreen, very dark prominent black-purple median and apical bands,
these bands are also promenent on the middle and hind legs,
median fainter on rear, tips of tibia blackish, for tarsl ration
the first section is 45% the length of the second.
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Stenacron Larvae & Adults 2020
Forewings; (some sample may have black longitudinal viens),
costal, subcostal, R1 veins yellow turning brown in bulla area
till stigma, R2 and all other logituninal veins brownish and same
with crossveins, in the costal subcostal interspaces from
costalbrace to bulla less than 5 heavliy blackend crossveins
then a blank area, 3 in the bulla, then blank again, from the
base of stigma stain to tip ofet 9-13, stigmac stain yellow
turning brown-gray-green and going over the apex of the wing,
black intercalaries spots in the right wing, 2-3 crossveins in
the bulla area with costomary black dash. Hindwing costal,
subcostal, and R1 brown with yellow colored membraine, out margin
black shaded.
Abdomen; (background coloring highly variable do to geological
substrate composition). Often hyaline-white but many sample
yellow-cream, median germinant line rarely, but it may connect
to the posterior edge of forward tergite like canadense, in
light types this median line can be completely absent see the
leopard larva changed its spots in larva book for adult male
with no median line at all, making it look like frontale,
moderate to large submedial pale spots that are not arranged to
form a submedial line, heavy piceous sublateral shading from
tergites 1-5, on 6-9 may not connect to forward tergites,
moderate to very large spiracular spots, often infused or in
capsulated within the transverse bands, tergites 1-9 blackpurple transverse bands wide and often turning black in spiracle
area, median line on tergite 10 short if present, tergites 8-10
commonly orangey-brown sometimes with cast of reddish stain.
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Tails; pale yellow turning smoky
darker articulations.
brown
in apical
area,
with
Genitals; without question allied to frontale, distinguished
from frontale by the sublateral basal spines. Frontale has a
lateral cluster, with rarely 1 or 2 basal spines; ohioense has
3-6 basal lateral spines often like a small cluster. Ohioense
also does not have a true lateral spine cluster they are broken
apart see anatomy section.
pallidum
Traver 1933 / 1935
Synonym free
Notes; based more on Traver 1933 than 1935. She was more descriptive in
1933, so this is a combination of both. In the photo plate section of this
book there is a female sample that aligns with this species from Lake
Norris TN 2014. Although not yet reported in that state the size eliminates
all others in the genus as this female sample was 7.5 mm.
Body size; 6.5-7 ♂ mm, 6-7.5 ♀ mm
Forewing size; 7.5-8 ♂ mm, 9-10 ♀ mm
Tails; 20-22 ♂ mm, 17 ♀ mm
Head; pale yellow to darker yellow on the vertex that is
standard for the genus, maybe even hyaline on the lower area of
the clypeus, a fine dash underneath each antenna scape, a small
black spot near the compound eyes, a red spot on the vertex, in
this genus that represents the palmen body at the cranium
suture, although not stated all Stenacron have some form of
black or very pale gray spots on the vertex on either side of
cranium suture, she did not comment on black ringed ocelli.
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Stenacron Larvae & Adults 2020
Pronotum; hyaline as most light forms are in the genus with fine
dark gray or black streaks in the lateral areas of the pronotum.
Notum; pale yellow to yellow tan unmarked, not stated but
typically Stenacron of very pale forms have either a yellow or a
white scutellum.
Pleura; slightly deeper yellowish, with a deeper orange spot on
either side of the rear coxa, maybe slightly orange in front of
the middle coxa as in many forms in the genus.
Legs; yellowish-white, fore femora deep yellowish with a cast of
brown, conspicuous purplish-black median and apical bands, fore
tibia purplish-black at the apical area, joining of fore tarsi
faintly brown, fore tarsal ration the first segment is basically
equal to the second, middle and hind femora pale yellow-hyaline
with median and apical band just fainter, hind median band my be
restricted to a dorsal line.
392
Stenacron Larvae & Adults 2020
Forewings; (illustrations based on descriptions a sample that
aligns with this species). Costal, subcostal, R1 veins yellowbrown, stigma stain pale (she does not comment on over apex but
most in the genus do) as does aligning sample, 2 or 3 crossveins
in the bulla area with dumbbell shaped black dash. Hindwing may
have slight basal tinge with darkened hind margin.
Abdomen; whitish 1-7 semi-hyaline, 8-10 opaque faintly yellowish
dorsally, each tergite with rather widely margined posteriorly
with purple black, meaning moderately wide purplish-black
transverse bands, without spiracular spots.
Tails; pale, so whitish-hyaline without articulations
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Stenacron Larvae & Adults 2020
proximum
Traver 1935
Notes; only one description exists for this form in the Biology of Mayfly
1935. This description in based on that description but more so on reared
adults from Southern Ontario that align with the historical profile. The
form conjunctum is almost inseparable from proximum but in comparative
discussions, variation and maculation we clarify the two forms from each
other.
Body sized; 9-9.5 ♂ mm, 11 ♀ mm
Forewing size; 10 ♂ mm 12 ♀ mm
Tails; 22-26 ♂ mm
Head; pale yellow with a very slight median crania shading,
below on the frontal margin a blackish spot on either side of
the median cranium structure, dash below each antenna bases,
small black spots at the corners of the compound eyes, brownishorange shading around the ocelli, and ocelli not black ringed,
Strong red spot at the palmen body, small black spots on the
vertex, posterior margin brownish terminating in black shading.
394
Stenacron Larvae & Adults 2020
Pronotum; hyaline with slight yellow lateral
streaks in the lateral areas no other markings.
edges,
black
Notum; deep reddish-chocolate brown in the upper most median
area, paler laterally with a bubble-gum-tan coloring, scutellum
often tipped with yellow.
Pleura;
principally
yellow
with
cast
of
orangey-brown,
moderately pronounced blackish-brown pleura streaks, fore coxa
bright yellow, fore and hind wing roots hyaline.
Legs; yellow with middle and hind being paler almost whitish on
the rear, fore femora, deeper yellow with moderate to prominent
median and apical bands, fore tarsal ratio first segment is
basically equal to the second.
Forewings; costal, subcostal, R1 veins yellow brown throughout
with pale yellowish-red stigma stain not going over the apex
this is rare in the genus, wings spares of crossveins
throughout, typically 2 in the R1&R2 area below the bulla with
two black spots seldom a black bar.
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Stenacron Larvae & Adults 2020
Abdomen; most samples yellow-white, summer sample whitish-paleyellow, germinant medial stripe from 1-7 sometimes only 1-5,
often sublateral anterior shaded points see arrow, blackish
tergite banding 1-9, 10th un marked, 1-9 brown transverse shading
fine black or gray spiracular spots often incorporated with the
black transverse bands, 8-10 rusty-reddish-brown with the 10th
ending with a orangey tone but muted.
Tails; yellowish basally turning dusky with
articulations, so one thin one fat and so on.
alternating
fine
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Stenacron Larvae & Adults 2020
Table of key features
397
Stenacron Larvae & Adults 2020
Pronotum spots, pleural streaks, and spiracular all are good for
a reasonable diagnosis. Male genitals are the best proof of
form. Always keep in mind geological variations should be
considered the nearest form.
1; full body length from head to the beginning of the tails
2; forewing length from the base to the tip
3; complete line across frontal shelf
4; median crania spot
5; median crania shading
6; dashes or spots below antenna bases
7; spot in the corner of the compound eyes on the face
8; spots on the vertex or top of the head
9; oblique lateral black streaks on the pronotum
10; median stripe on the notum or top side of thorax
11; spots forward and above forewing root
12; pleura streaks, stripes in front of middle hind legs
13; spots on the coxa either F front, M middle, R rear legs
14; stigma stain going over the apex of the forewing
15; longitudinal vein color in the forewings
16; shading on the posterior edge of the hind wings
17; abdomen background color
18; transverse bands at the posterior margin of tergites
19; shading on the anterior area of the transverse bands
20; sublateral shading on the sides of the abdomen
21; spiracular spots on the side of the abdomen often black
22; median stripe on the top of the abdomen
23; color of the tails + articulations or banding
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Stenacron Larvae & Adults 2020
Stenacron adult Male features and key
From darkest to lightest
Anatomical
Features
1
2
3
canadense
gildersleevei
dark form
ohioense
8-9 mm
9-10 mm
full smile
on female
infused
infused
10-11 mm
10.5-11 mm
full smile
connected
infused
infused
9 mm
10 mm
yes not connected
line
yes
black spots
LRG black
germinate
line
LRG
yes
LRG black
purp-black
no
LRG
red shading
LRG black
germinate
yes-
yes-
yes-
yes-BLK
F-M
brown-red
yes
yell-brown
16
17
18
19
20
hindwing shading
AB ground color
transverse bands
trans-V-shading
sub-lat-shading
NAR-black
yellowish
yes
heavy gray
heavy gray
no
F-M-R
pale brown
yes
yellow
milky
NAR dusky
hya-yellow
heavy black
heavy black
heavy black
yes-BLK
F
brown-yell yes
15
body length
forewing length
frontale shelf
line
midcrania spot
midcrania
shading
marks below ANT
spots comp-eye
vertex marks
pronotum marks
notum mid-streak
marks antforewing
pleura streaks
coxa marks F M R
stigma stain /
over apex
long-vein color
21
spiracular spots
no /with
BLK shading
LRG
distinct
LRG distinct
22
23
medial stripe
tail color + ART
yes wide
pale smoky
+ ART
4
5
6
7
8
9
10
11
12
13
14
infused
infused
yellow
black
hyaline
heavy black
heavy black
heavy black
heavy black
yes wide
yellowyellow no ART
brown no
ART
Females can be identified by all characters but are larger
399
Stenacron Larvae & Adults 2020
Stenacron adult Male features and key
From darkest to lightest
Anatomical
Features
1
2
3
15
16
17
body length
forewing length
frontale shelf
line
midcrania spot
midcrania
shading
marks below ANT
spots comp-eye
vertex marks
pronotum marks
notum mid-streak
marks antforewing
pleura streaks
coxa marks F M R
stigma stain /
over apex
long-vein color
hindwing shading
AB ground color
18
transverse bands
19
20
trans-V-shading
sub-lat-shading
21
spiracular spots
22
23
medial stripe
tail color + ART
4
5
6
7
8
9
10
11
12
13
14
light form
ohioense
frontale
9 mm
10 mm
somewhat
8 mm
9 mm
somewhat
9.5-10.5 mm
11 mm
no
infused
infused
yes
yes
yes
no
line
LRG
blk stripes
LRG black
yes
line
small
blk spots
sm blk
germinate
no
line
small
yes
sm blk
yes
no
yes prom
M
LT brown
not over
yell-brown
NAR brown
yell-brown
yes moderate
M
amber not over apex
fine blk
fine blk
fine gray
pale gray
pale gray
no
moderate
distinct
germinate
pale + ART
LRG distinct
yes-
yes prom
F-M-R
green-brown
yes
green-brown
purp-blk
yellowgreen
moderate
blk
pale-gray
moderateblk
prominent
infused
germinate
smoky-brown
majus
amber-yell
dusky
creamy-yell
germ 1-4
white + ART
Females can be identified by all characters but are larger
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Stenacron Larvae & Adults 2020
Stenacron adult male features and key
From darkest to lightest
Anatomical
Features
1
2
3
15
16
17
18
19
20
21
body length
forewing length
frontale shelf
line
midcrania spot
midcrania
shading
marks below ANT
spots comp-eye
vertex marks
pronotum marks
notum mid-streak
marks antforewing
pleura streaks
coxa marks F M R
stigma stain /
over apex
long-vein color
hindwing shading
AB ground color
transverse bands
trans-V-shading
sub-lat-shading
spiracular spots
22
23
medial stripe
tail color + ART
4
5
6
7
8
9
10
11
12
13
14
proximum
conjunctum
minnetonka
9-9.5 mm
10 mm
no
8 mm
9 mm
broken line
9-10 mm
10-11 mm
full smile
no
yes
yes
no
yes-Daggy
no
line
small
yes
sm black
germinate
no
line
small
yes
yes
germinate
no
line
small
yes
yes
no
no
moderate
M
yell-green
not over
yell-brown
dusky
pale yellow
fine blk
pale brown
1-5 gray
fine
defused
1-7 germ
yell dusky
moderate
no
yell-brown
over apex
yell-brown
pale brown
hyaline
fine brown
pale brown
1-3 brown
fine defused
no
M-R
yell-brown over apex
1-4 germ
white + ART
no
pale + ART
yell-brown
purp-brown
yell-white
yes
faint gray
no
LRG distinct
Females can be identified by all characters but are larger
401
Stenacron Larvae & Adults 2020
Stenacron adult Male features and key
From darkest to lightest
Anatomical
Features
candidum
carolina
pallidum
6.5-7 mm
7.5-8.5 mm
1
2
body length
forewing length
7.5 mm
8.5 mm
3
frontale shelf
line
midcrania spot
midcrania
shading
marks below ANT
spots comp-eye
vertex marks
no
10 mm
10.5-11.5
mm
no
very dark
no
no
no
no
pale Y/N
spots
small
mid stripe
line
tiny
reddishline
fine blk
no
no
dash
tiny
red spot
4
5
6
7
8
9
10
11
12
13
14
pronotum marks
notum mid-streak
marks antforewing
pleura streaks
coxa marks F M R
stigma stain /
over apex
15
16
17
18
19
long-vein color
hindwing shading
AB ground color
transverse bands
trans-V-shading
20
21
22
23
sub-lat-shading
spiracular spots
medial stripe
tail color + ART
yes
no
no
no
faint gray
pale
reddish
over apex
yell-brown
NAR black
yell-white
blk
no
no
distinct
no
orange spot
no
no
yell-brown
over apex
no
no
red-brown over apex
amber-brown
pale gray
hyaline
fine black
GRY rapping
sternum
no
no
no
dark-smoky
pale amber
dark brown
hyaline
yes
pale brownish
no
no
distinct
no
no
no
white no
hyaline
art
Females can be identified by all characters but are larger
402
Stenacron Larvae & Adults 2020
Stenacron adult Male features and key
From darkest to lightest
Anatomical
Features
1
2
3
4
5
6
7
8
9
10
11
12
13
14
body length
forewing length
frontale shelf
line
midcrania spot
midcrania
shading
marks below ANT
spots comp-eye
vertex marks
pronotum marks
notum mid-streak
marks antforewing
pleura streaks
coxa marks F M R
stigma stain /
over apex
15
16
17
long-vein color
hindwing shading
AB ground color
18
19
20
21
22
23
transverse bands
trans-V-shading
sub-lat-shading
spiracular spots
medial stripe
tail color + ART
areion
affine
7 mm
8 mm
fine dash
7-8 mm
8-9
no
no
no
no
no
no
not known
no
yes
not known
not known
faint dots
minute
spots
no
no
no
no
M
brown over
apex
unknown
unknown
unknown
hyalinewhite
blk-brown
brown
no
no
9th germ
white no
art
no
no
yell-brown
over apex
flaveola
same as
interpunctatum Say
hya-amber
NAR brown
hyaline
purp-black
pale gray
no
no
no
white no art
Females can be identified by all characters but are larger
403
Stenacron Larvae & Adults 2020
Stenacron adult Male features and key
From darkest to lightest
Anatomical
Features
1
2
3
15
16
17
18
19
20
21
22
body length
forewing length
frontale shelf
line
midcrania spot
midcrania
shading
marks below ANT
spots comp-eye
vertex marks
pronotum marks
notum mid-streak
marks antforewing
pleura streaks
coxa marks F M R
stigma stain /
over apex
long-vein color
hindwing shading
AB ground color
transverse bands
trans-V-shading
sub-lat-shading
spiracular spots
medial stripe
23
tail color + ART
4
5
6
7
8
9
10
11
12
13
14
heterotarsale
floridense interpunctatum
9 mm
11 mm
no
7-9 mm
not known
no
7.5 mm
7.5-8.5 mm
no
no
no
no
no
no
no
no
minute
blk-spots
no
no
no
no
sm gray
gray spots
yes
no
no
line
minute
blk spots
fine
no
no
no
no
amber over
apex
yellow
NAR dusky
hya-yellow
blk fine
no
no
no
no
no
no
yellow over
apex
yell-gray
dusky
hyaline
fine black
no
no
no
no
no
no
yell-brown over apex
hya + art
lt gray
yell-hyaline
yell-brown
blackish
hyaline
fine black
fine gray
no
no
sm medial 1-4
Females can be identified by all characters but are larger
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Stenacron Larvae & Adults 2020
Credit for usage of photos
• The Centre for Biodiversity Genomics; 2 photos by Jeff Webb of
♀ larva floridense.
• Sharon Moorman; complete photo series of carolina ♂
sample
imago, samples we believe to be pallidum ♀ imago, frontale ♀
larva, ♂ larva that align with floridense, and adult ♀ imago
that also align with
floridense, ♂ carolina larva, all
samples from Norris lake TN.
• Brandon Woo; Norway Maine
interpunctatum / majus.
for
his
perfect
sample
of
a
♂
• Brandon Woo; affine photos from the Cornell collection.
• Charley Eiseman Black River Wisconsin; one ♂ sample that
aligns with minnetonka, and a rare photo of what aligns very
well with Burk’s 1953 areion ♂.
• Tom Murry for his picture of what we believe to be the larva
of pallidum
• Joshua Doby for photos of S carolina larva from Ashville NC.
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Stenacron Larvae & Adults 2020
Pronouncing names and words
Saying the name right or pronouncing complex words make this
very hard for everybody. However the correct Latin and
biological terms are the best to use. Remembering a few years
back trying to learn this stuff and it is not easy. But, once
you got it you got it.
So this is the place and time to learn how to talk the talk
shall we say. First let’s look at pronouncing all the names
mentioned in this genus.
STENACRON
= [sten-ah-cron]
AFFINE
= [a-fine]
AREION
= [air-e-on]
CANADENSE
= [can-ah-dense]
CANDIDUM
= [can-did-um]
CAROLINA
= [car-o-line-a]
CONJUNCTUM
= [con-junk-tum]
FLAVEOLA *
= [fla-vee-o-la] *
FLORIDENSE
= [flor-ah-dense]
FRONTALE
= [fron-tull]
GLIDERSLEEVEI
= [gil-der-slee-vah]
HETEROTARSALE
= [he-ter-o-tar-sal-ly]
INTERPUNCTATUM = [in-ter-punk-ta-tum]
MAJUS
= [may-jus]
MINNETONKA
= [min-knee-tonk-ah]
OHIOENSE
= [o-hi-o-ense]
PALLIDUM
= [pal-li-dumb]
PROXIMUM
= [prox-e-mum]
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Stenacron Larvae & Adults 2020
There that is all the names you need
the names in that list is no longer
inside the text. It is marked with a
words that are typed in red are very
text of these guides.
to be able to say. One of
in usage, but it will be
star *. From here out any
important and used in the
This section is the technical terms used when a description is
made. As stated these are the correct words and best ones used.
So if you take the time to know them now, it will make your
reading that much easier.
Abdomen; [ab-duh-mun-n] This is the rear section of the insect
regardless of its stage in the life cycle. It will have 10
sections.
Abdominal;
cavity.
[ab-dom-muh-nl]
Referring
to
the
entire
abdomen
Adult; [uh-duhlt] The fully grown stage of the mayflies life.
Having only 2 tails and 4 wings. Two large wings and two small
wings.
Antenna; [an-ten-uh]
Meaning, there are two single small
antenna or segmented like hairs on the head of the insect. On
the larva they are on the front top of the head, and in the
adults they are on the lower face area.
Antennae; [an-ten-ae]
to the pair.
Meaning, more than one antenna referring
Anterior; [an-teer-ee-er]
the very
anteriorly; in front of something.
front
of
something,
or
Apex; [ey-peks]
The very furthest end, or at the end. At the
very top of the forewing the rounded over area. Opposite of
basal or base of something.
Apical;[ah-pick-al] referring to the apex of something.
Basal & base;
[bey-sul]
the base of something typical usage,
the basal end of the abdomen meaning; the beginning of the
abdomen segment #1.
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Crania; [krey-nee-ia]
Meaning; in the adult insect in the
center area just above the very bottom of the face. Elevated
keel like edge.
Cranium;
[krey-nee-uh-m]
the upper part of the head near the
vertex between the compound eyes.
Cranium suture; typically Y shaped area that joins the 3 primary
areas of the head capsule.
Clypeus;
[klip-ee-uh-s]
in the larva this is the very front
leading edge just above the labrum. In the adult is where it is
used the most and it pertains to the lowest area of the face.
Costa or costal vein; [kos-ta] & [kos-tl] rib like vein in the
further most anterior edge the wings. In the forewing it is
typically yellowish-gray in color.
Denticle;
[den·ti·cle]
a small
projection typically on the claw.
Depressed; [de-press-ed]
pressure
Dorsal;
tooth
or
tooth-shaped
biology flattened, as if from downward
[dor-sal] the upper area or top of the insect.
Elliptical; [el-lip-ti-cal] elongated oval shape
femora;
[fem-o-ra] A plural of femur.
Femur;
[fe-mur]
zoology a
thighbone in other vertebrates
fimbriated; [fim-bri-ated]
have a fringed border.
Frontal;
[fron-tul]
bone
describes
equivalent
parts
of
to
the
organisms
human
that
pertaining to the front edge.
Fuliginous; [fu·lig·i·nous] having the color or consistency of
soot or smoke.
Fulvous-tawny; [ful·vous]-[ taw·ny]
color of the common deer.
Fuscous; [fus·cous] dark brown approaching black.
Humeral;
[hum-er-al] the first and lowest cross vein in the
forewing near the wing root.
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Stenacron Larvae & Adults 2020
Hyaline; [hy·a·line] resembling
transparency; glassy.
glass,
as
in
translucence
or
Imago; [im-a-go] an insect in its sexually mature adult stage
after final metamorphosis.
Infuscated; [In-fus-ca-ted] (Zoology) darkened with a blackish
tinge.
Interrupted;
uniformity.
[in-ter-rupt-ed]
to
break
the
continuity
or
Labium; [ley-bee-uh] the lower lip of an insect.
Labrum;
[la-brum] the upper lip of an insect.
Larva; [lahr-va] Entomology. the immature, wingless, feeding
stage of an insect that undergoes complete metamorphosis.
Larvae;
plural mean more than one larva
Lateral; [la-ter-al] relating to the sides of the insect.
Laterally; [la-ter-al-ly] sideways; moving towards the sides of
the insect.
Mandibles; [man-duh-buh-l]
teeth and molars.
the
bone
of
the
lower
jaw
having
Maxilla;
[mak-sil-uh] the upper part of the jaw on the insect
having comb like teeth.
Maxillae;
[mak-sil-ee] plural mean two maxilla.
Mesonotum; [me-so]-[noh-tuh-m] the middle area of a dorsal plate
or sclerite of the thorax of an insect. The middle of the upper
area of the thorax.
Metanotum;
[mee-tuh]- [noh-tuh-m] the rear area of the notum.
Rear upper area of thorax.
Notum;
insect.
[noh-tuh m] the upper dorsal plate or thorax of the
Ocelli;
[oh-sel-ahy]
a
type
of
simple
eye
common
to
invertebrates, consisting of retinal cells, pigments, and nerve
fibers.
409
Stenacron Larvae & Adults 2020
Piceous; [pis-ee-uh-s] color of pitch or very close to blackbrown color.
Pectinate;
[pek-tuh-neyt]
formed
into
or
parallel, tooth-like projections; comb-like.
Pectinate setae comb; A type
anterior edge of the maxillae.
Pleura;
of
comb-tooth
having
on
the
closely
crown
or
[ploo r-uh] the side of the thorax.
Pronotum; [proh-noh-tuh m] same as prothorax the most forward
part of the thorax right behind the head and forward of the
notum.
Scutellum; [skyoo-tel-uh m] Zoology. a small plate, or other
shield-like part, as on the thorax of insects.
Setae; [see-tuh]
very fine hair like appendage.
Subimago; [sub-im-a-go] the first winged stage of the mayfly,
with dull opaque wings, known to anglers as a dun, before it
metamorphoses into the shiny glassy imago or spinner See also
dun.
Sublateral;[sub]-[la-ter-al]
median area.
less
than
lateral
towards
the
Submedial; [sub]- [mee-dee-uh-l] less than the middle, slightly
off center.
Thorax; [thawr-aks] Anatomy. the part of the trunk in humans and
higher vertebrates between the neck and the abdomen, containing
the cavity, enclosed by the ribs, sternum, and certain
vertebrae, in which the heart, lungs, etc., are situated; chest.
Tawny; [taw-nee] of a dark yellowish or dull yellowish-brown
color or orangey brown.
Tibia; [tib-ee-uh] (in insects) the fourth segment of the leg,
between the femur and tarsus.
Tarsus; [tahr-suh-s] the distal part of the leg of an insect,
usually subdivided in the adult into two to five segments.
Venter;
[ven-ter]
underside of the abdomen or belly.
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Stenacron Larvae & Adults 2020
Ventral; [ven-truh-l]
of or relating to the venter or belly;
abdominal. Anatomy, Zoology. situated on or toward the lower,
abdominal plane of the body; equivalent to the front, or
anterior, in humans.
Selected bibliographies of Reference 1681-2017
If they are available all of the following papers can be located
at;
http://www.ephemeroptera-galactica.com/mfbib.php
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Banks N. 1910. Notes on our eastern species of the May-fly genus
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Banks N. 1914. New neuropteroid insects, native and exotic.
Proceedings of the Academy of Natural Sciences of Philadelphia
Berner L. 1950. The Mayflies of Florida. University of Florida
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Berner L; Pescador ML. 1988. The Mayflies of Florida. Revised
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Burks BD. 1953. The mayflies, or Ephemeroptera, of Illinois.
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Daggy RH. 1945. New species and previously undescribed naiads of
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Flowers RW; Hilsenhoff WL. 1975. Heptageniidae (Ephemeroptera)
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Ide
FP. 1930. Contribution to the biology of Ontario mayflies
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The End
Thank you for reading my book
I hope you enjoyed it as much
As I did making it.
Cover illustrations are both
Interpunctatum / proximum
luteum stenonema