Purple Emperor

Apatura iris

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Apatura iris

Male, Italy, July 2014

Apatura iris

Male, Switzerland, July 2016

Male, Italy, July 2014

Apatura iris and Limenitis camilla

Male (wings closed) with a white admiral, Switzerland, June 2018

Apatura iris

Female, Switzerland, July 2018

Apatura iris

Territorial flight above canopy, Switzerland, July 2016

Male, Switzerland, July 2009

Male, Switzerland, July 2009

Male, June 2006, Oxfordshire

The same male viewed from a different angle

Female, Switzerland, August 2011

Same female, showing a glimpse of the upperside

Female, Switzerland, July 2011

Male, Val d'Aran, July 2000

Male, Val d'Aran, July 2004

Male, July 2005, Val d'Aran

Male, Val d'Aran, July 2001

Egg, Switzerland, August 2010

First instar caterpillar, August 2010

Detail from the same photo.

Third instar larva, September 2011, Switzerland

The same larva - just under 1cm long

The same larva, immediately prior to hibernation

Apatura iris hibernating

A hibernating larva

Apatura iris hibernating

An alternative hibernation site

A caterpillar after hibernation - May 2010, Switzerland.
This individual is soon to shed his skin.

The caterpillar rests for the night on the mid-vein of the leaf. The picture shows the charactaristic nibbling to either side.

This is the same caterpillar a couple of days later, after shedding his/her skin

A more mature caterpillar, Switzerland, May 2010

Another caterpillar, Switzerland, May 2010

May 2010

A fully mature caterpillar, June 2010

A pupa, June 2010, Switzerland

See HERE for the full life cycle of this species, including a video of its emergence from the chrysalis

Apatura iris distribution

Distribution

The purple emperor is a forest butterfly, widely distributed and often common in most of Europe except the far north and the far south. It is nevertheless quite elusive, spending much of its time in the canopy, where males disport themselves around master trees and females go to pick up males. Males do come to ground in the mornings, usually singly, to sup at minerals, carnivore droppings or carrion, and when engrossed in this activity may be closely approached - but never approach until they have actually started feeding, or they will fly up, swoop around you a few times and then zoom off to find another spot. Typical places are rides, where males seem to command linear territories. Females come to ground less but I have seen them taking minerals and also at sap on cut trees.

Only the males sport the purple, and only from certain angles. The colour is produced by refraction, not pigmentation, so what seems a gleaming blue butterfly one moment may appear sooty brown the next. For this reason, colour is not the best way to sex this species. The female is larger, has rather broader, rounder wings and generaly a broader white stripe on the hindwing. She spends a lot of time 'striking' sallows - the term of art for zooming in to look for laying sites - but males often sit in sallows too, so it should not be assumed that an emperor in a sallow is a female. In western Europe the only butterfly the purple emperor might be confused with is the nominate form of lesser purple emperor. This is very similar above but has an orange ring in s.3 of the forewing and lacks a tooth in the white band on the hindwing. Beneath, the white band on the hindwing is ill-defined, especially outwardly. The purple emperor has a clearly demarcated band here.

I have spent a lot of time monitoring eggs, caterpillars and pupae of this species in the wild. Pictures and descriptions of all stages and instars can be found here. Eggs are laid in July and August on the upperside of sallow leaves in half-shade. When laid they are pale green but a dark band develops at the base in a day or so. Later, this band migrates to the top of the egg where it becomes the head of the caterpillar within. The caterpillar emerges some two weeks after the egg is laid. First, it pushes up the top of the egg, which opens like a little umbrella. Then it sets about eating the egg - its first meal. When the egg is reduced to the basal disk, the caterpillar moves to the tip of the leaf and takes up residence there. It will spend the rest of its life, between bouts of eating, sitting in the tips of leaves - often but not always the same leaf for an entire instar. The exception to this is the third instar, because it is at this stage that the caterpillar moves off to hibernate on a bud, twig or stem of sallow. In March, if it has not hibernated next to a leaf bud, it moves again be next to one. As soon as the leaves begin to unfurl, some time in April, it begins eating ravenously and resumes growth. At the end of its fifth instar it moves off to pupate and emerges a couple of weeks later, usually in the second half of June or in July. In Switzerland, the species has a long flight period, from June through to September. In the UK the action is usually all over by mid-August.