318 



FOREST ENTOMOLOGY. 



Pemphigus bursarius (Hart.) 



This species is found on the leaf-stalks of poplar (fig. 290), chiefly 

 on the black Italian species, the black burry poplar, and also on the 



young woody twigs of the Lombardy pop- 

 lar. The gall is smooth, globular, highly 

 coloured, and with an opening at the side. 

 In July or August the leaves, with galls on 

 the foot-stalks, having fallen prematurely, 

 may be picked up, and the insects found 

 in all their respective stages of metamor- 

 phoses. 



The stem-mother (fig. 291) is larger than 

 any of her progeny. The legs are short, 

 and the creature comparatively helpless. 

 The antennae are four-jointed, and the corn- 

 icles absent. 



The larva (fig. 292) is of a very light- 

 green colour. 



The pupa (fig. 293) is of a pale-green 

 colour, with a slight mealy dusting, and shows signs of wings at a 

 very young stage. The antennae are longer than in the green aphis, 

 but the joints are not easily distinguished. 



Fig. 290. Gall on leaf-stalk of 

 poplar caused by Pemphigus 

 bursarius. 



Fig. 291. "Stem-mother" of Pemphigus bur- 

 sarins. (From camera-lucida sketch.) 



Fig. 292. Larval stage of Pemphigus bur- 

 sarius. (From camera-lucida sketch.) 



The winged viviparous female (fig. 294) is black, and the body and 

 wings are dusted over with a white powdery matter. The antennas are 

 six-jointed, the third joint being the longest ; and the third, fourth, 

 fifth, and sixth are ringed. Buckton says the sixth joint is smooth, 



