InfluentialPoints.comBiology, images, analysis, design...
| Aphids | Find them | How to ID | ID by host |
| InfluentialPoints.com Biology, images, analysis, design... |
|
"It has long been an axiom of mine that the little things are infinitely the most important" |
|
|
Diuraphis frequensCouch grass aphidOn this page: Identification & Distribution Other aphids on the same host Damage & ControlIdentification & DistributionAdult apterae of Diuraphis frequens (see first picture below) are very elongate, green, powdered with grey wax, with the head darker, and blackish appendages. Their antennae are only about 0.3 as long as the body, with the terminal process 1.05-1.5 times as long as the base of antennal segment VI (cf. Diuraphis holci, which has the terminal process 1.3-1.9 times its base). The rostrum is short, nearly reaching the second pair of coxae, with the apical rostral segment (RIV+V) 0.5-0.75 times the second hind tarsal segment (HTII) (cf. Diuraphis tritici, which has RIV+V 0.9-1.15 times HTII). The abdomen has sclerotic stigmatic plates and sclerotic crossbars on tergites VII and VIII. There is no supracaudal process on abdominal tergite VIII, and usually no marginal tubercles on abdominal tergites II-VI (cf. Diuraphis noxia, Diuraphis mexicana & Diuraphis muehlei, which have a supracaudal process on tergite VIII, and marginal tubercles on at least tergites III-V). The siphunculi are very short dark cylinders about 0.25 times the caudal length, with apertures directed backwards. The siphunculi are placed equidistantly from the spiracles on abdominal segments VI and VII (cf. Diuraphis holci, which has the siphunculi placed closer to spiracle on segment VI than to that on VII). The cauda is dark and sclerotic with 5 or 6 hairs. The body length of an adult Diuraphis frequens aptera is 1.3-2.1 mm. Note: The 3 Diuraphis species mentioned above (Diuraphis noxia, Diuraphis mexicana & Diuraphis muehlei), which have a supracaudal process & marginal tubercles on II-VI, are in the nominate subgenus Diuraphis, whilst Diuraphis frequens and Diuraphis holci, which lack the process and have no marginal tubercles on II-VI, are in subgenus Holcaphis.
Images copyright Frank Peairs, Colorado State University, Bugwood.org under a Creative Commons licence. The alate Diuraphis frequens has a green body. The antennae are about 0.5 times the body length, and bear 4-8 secondary rhinaria on segment III, and 0-2 rhinaria on segment IV. The legs are much longer than in apterous viviparous females, but other characteristics are similar.
Images above copyright CBG Photography Group under a Creative Commons License. The clarified slide mounts below are of adult viviparous female Diuraphis frequens : wingless, and winged.
Micrographs of clarified mounts by permission of Roger Blackman, copyright AWP all rights reserved. The most common host of Diuraphis frequens is couch grass (Elymus repens). It has also been recorded from other grass genera such as cockspur grass (Echinochloa), barley (Hordeum), rye grass (Lolium) and wheat (Triticum). After hatching the fundatrices penetrate between unrolling leaves of couch grass and stop their growth, which results in a bunch of rolled leaves at the apex of the plant. Colonies of Diuraphis frequens live in the rolled leaves, with alatae appearing in the third generation. In October sexuales appear with both the oviparae and males being apterous. Diuraphis frequens is widespread, and sometimes common, in Europe, Asia and North America. Other aphids on the same hostDiuraphis frequens has been recorded on 4 Elymus species (Elymus caninus, Elymus dahuricus, Elymus glaucus, Elymus repens).
Diuraphis frequens has been recorded on 1 Triticum species (Triticum aestivum).
Damage and controlDiuraphis frequens is mainly found on wild grasses, especially couch grass. It has, however, been recorded on wheat (Triticum aestivum). Robinson (1997) reported it as having reached pest numbers on wheat in Finland in summer 1997. He considered that its relative abundance during that year may have resulted from the unusually hot dry weather, and felt that Diuraphis frequens was unlikely to become a serious pest of wheat. We note that this conclusion may have to be revised given accelerating climate change.
|
