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Poplar-spruce aphidsOn this page: Pachypappa Pachypappa tremulae Pachypappa warshavensis
There are about 13 species which host alternate between Populus (poplar) species and the roots of Picea (spruce).
Pachypappa tremulae (Aspen-spruce aphid)
In springtime Pachypappa tremulae fundatrices (not shown here) may be found on the twigs of aspen (Populus tremula). They are unusually large (body length 5.0-6.6 mm) and are almost globular. They are a dirty reddish or yellowish brown colour, but appear silvery as they are covered with long fine hairs. They have no siphuncular pores and do not secrete any wax. The offspring of the fundatrix move on to the new shoots and form a rosette like leaf nest (see first picture below) formed by bending of the leaf petioles and stunting of growth of the shoot.
Guest images copyright Volker Fäßler, all rights reserved
These offspring all develop to winged individuals (see second picture above) which are orange or reddish brown, covered in wax and with very small siphuncular pores. They migrate in June to form colonies on the roots of spruce (Picea abies). Pachypappa tremulae apterae on spruce are pale yellowish white with tufts of wax posteriorly. Sexual forms then return to aspen in autumn.
Pachypappa tremulae is widely distributed in the northern palaearctic, east to China and Japan.
Pachypappa warshavensis (Poplar leaf-nest gall aphid)
Pachypappa warshavensis forms loose leaf nest galls (see two pictures below) among leaves of white poplar (Populus alba), grey poplar (Populus canescens) or Euphrates poplar (Populus euphratica). The wingless fundatrix is reddish-brown with a body length of 3.5-4.0 mm. The offspring of the Pachypappa warshavensis fundatrix have a reddish brown abdomen - immatures are shown in the first picture below. They all develop into alates (see second picture below) with a body length of 3.0-3.2 mm.
Images copyright Dr László Érsek, all rights reserved.
A distinguishing feature of the adult Pachypappa warshavensis is the absence of small hairs on the forewing membrane (cf. Pachypappa vesicalis which has small hairs on the membrane of its forewing). Also there are 4-6 secondary rhinaria with thick sclerotic rims on the third antennal segment, often confined to the distal half of that segment.
Feeding on poplar leaves is concentrated on the petioles, which causes the leavers to fold over, thus creating a leaf nest. The alate Pachypappa warshavensis that develop in the leaf-nest are thought to migrate in June to the roots of poplar (Populus) and willow (Salix) species. Sexual forms return to poplar in autumn. Pachypappa warshavensis is found in Europe and central Asia.