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Pachypappa pseudobyrsaPoplar leaf-purse aphidOn this page: Identification & Distribution Biology & Ecology Interspecific association and Ant attendance Other aphids on the same hostIdentification & DistributionFeeding by Pachypappa pseudobyrsa fundatrices induces a small reddish-green blister-like gall (see first picture below) in the centre of the leaf near its mid-rib. This gall is open to the underside of the leaf. The fundatrix (second picture below, right of center), which lives in the gall, is yellowish olive green with a blackish head but is densely wax-covered. The fundatrix body length is 4.0-4.7 mm. She produces numerous progeny which leave the gall very soon after being born and spread out along the main veins. The leaf bearing the blister gall folds over to enclose the colony in a pseudogall. The orange immatures soon produce abundant wax which covers the aphids and the underside of the leaf (see third picture below). During May and June these immature Pachypappa pseudobyrsa develop into heavily waxed dusky-dark alatae.
Images above by permission, copyright Claude Pilon, all rights reserved. The alate Pachypappa pseudobyrsa (see picture below) has 5-8 secondary rhinaria with narrow sclerotic rims on antennal segment III, extending on to the proximal half of segment. The antennal terminal process is 0.17-0.21 times as long as the base of antennal segment VI. The apical rostral segment (RIV+V) is 0.60-0.75 times as long as the second hind tarsal segment (HT II) (cf. Pachypappa rosettei, whose RIV+V is 0.45-0.55 times HTII). The membrane of the forewing is without hairs (cf. Pachypappa sacculi, which has hairs on the forewing). Abdominal tergite VIII usually has a pair of well-developed wax pore plates. Siphuncular pores are absent. The genital plate has 6-12 hairs on the anterior half. The cauda has 3-5 hairs (cf. Pachypappa rosettei, which has a cauda with 10 or more hairs). The alate body is is about 3.5 mm long.
Image above by permission, copyright Claude Pilon, all rights reserved. Pachypappa pseudobyrsa is found on poplar (Populus) species, mainly eastern cottonwood (Populus deltoides) and quaking aspen (Populus tremuloides). Their life cycle is unknown, although it is likely that the alatae migrate to an unknown secondary host. Smith (1974), however, doubted this saying "due to the large size of the body in relation to the size and length of the wing, I question whether this species migrates. Certainly it could not be a very strong flyer because the wings are so short and delicate." Pachypappa pseudobyrsa is found in eastern North America, where it is widely distributed, and also in Colorado. Biology & EcologyInterspecific association and Ant attendanceOne of the colonies of Pachypappa pseudobyrsa photographed by Claude was a mixed species colony, in this case mixed with a Chaitophorus species (given the presence of pleural dorsal hairs most likely Chaitophorus populicola). The picture below shows an adult aptera of Chaitophorus populicola (blackish) with immatures of the gall causer - Pachypappa pseudobyrsa. There were also a number of immature Chaitophorus within the pseudogall.
Image above by permission, copyright Claude Pilon, all rights reserved. Mixed species colonies are quite often found in aphid galls and pseudo-galls, with other species taking advantage of the improved nutrition and protection offered by the gall. In this case there is also a very clear benefit to the host aphid. Normally Pachypappa pseudobyrsa is not ant-tended, but instead relies on the production of large amounts of wax to protect the aphids from predators. Hence it is not having to invest the considerable energy required to produce a honeydew especially attractive to ants. But Chaitophorus populicola is always ant-tended, and in this case the ants are attending (and presumably protecting) both aphid species (see picture below).
Image above by permission, copyright Claude Pilon, all rights reserved. Interestingly the, normally very waxy, Pachypappa are largely devoid of wax in this colony. In the presence of ants the Pachypappa pseudobyrsa appear to reduce wax production to a minimum.
Image above by permission, copyright Claude Pilon, all rights reserved. We have found a similar relationship between wax production and presence / absence of ants for Cinara costata. Other aphids on the same hostPachypappa pseudobyrsa has been recorded on 3-4 poplar species: (Populus deltoides ssp. deltoides, Populus deltoides ssp. occidentalis, Populus tremuloides and possibly Populus fremontii).
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