Pemphigus bursarias. 



In almost every part of England these galls are plentiful. 

 Some branches of the poplar have 25 per cent, of the leaves 

 attacked ; and where imagines have remained undisturbed for 

 several years, the galls are exceedingly numerous. Their multi- 

 plicity does not appear to retard either the growth of the twig 

 or that of the leaf. They are not difficult to obtain, since they 

 occur near the ground with as much frequency as on the upper- 

 most branches. They may also be found on the Lombardy 

 poplar {Populus fastigiata), a cultivated variety. The growth of 

 this gall is very similar to that caused by Tetraneum ulnii. In 

 this case, however, the queen pricks the cuticle of the petiole 

 (and occasionally the mid-rib), and not the blade of the leaf; 

 the sap, exuding from the punctures, steadily increases in bulk 

 until she is surrounded, and finally enclosed, with exception of 

 a very narrow opening at the apex of the gall. This material 

 forms a thick, fleshy wall of substance, intermediate in texture 

 between the wood and the leaf, which under magnification will 

 be seen to have a well-defined cellular structure. The shape of 

 the galls is variable. Mostly they are pyriform, and truncated 

 cone-shape ; some are elongated into an obtuse beak, while 

 others are subject to considerable genuflexion. Within the 

 cavity the queen brings forth a numerous brood of nymphs, 

 which with their rostra draw nourishment from the inner walls. 

 When arrived at the winged state, they make their exit through 

 the opening previously mentioned. 



The speckled appearance of the leaves is due to " honey- 

 dew," exuviae, and puparia. In the lower right-hand corner of 

 the illustration a very large twin gall may be seen ; and in the 

 left-hand corner two galls in section, the larger one being filled 

 with nymphs, the smaller one representing the gall after the 

 nymphs had been removed. 



The illustration is of specimens gathered at Hastings by the 

 author. 



