84 BRITISH APHIDES. 



The individuals are usually smaller than those of the 

 previous generation (No. 3), and seem already to have 

 commenced a degradation of form. The insects tran- 

 sport themselves from then' previous habitats, and 

 carry within them the embryos of the true sexes. To 

 these wing-ed forms Lichtenstein ofives the name of 

 '' Pseudogynes pupi/eres.^^ 



The last generation consists of males and females, 

 both of which are exceedingly small. This circum- 

 stance probably is the cause of their being so long 

 overlooked by early observers. The males are usually 

 apterous. Amongst the higher Aphides this sex is very 

 active and completely organised, but here the insects 

 are very simple in structure ; and from the fact that 

 their mouth organs are simply represented by buccal 

 prominences, which appear to be imperforate, they 

 must be quite incapable of feeding. The antennce also 

 are restricted in the number of their joints, which 

 would indicate, perhaps, a bluntness of sense as fur- 

 nished by those organs. 



The oviparous female is also, in many cases at least, 

 mouthless. The abdominal cavity shows only rudi- 

 ments of an alimentary system, and, indeed, it is 

 almost wholly occupied by the single ovum, which is 

 not much smaller than the insect itself. 



Shortly after impregnation, the female retires to some 

 chink or crevice under the bark, and there she dies, 

 often without delivering herself of her egg. In this 

 case the exuvias form a natural covering to the egg, 

 the dead body of the parent furnishing a nest for her 

 unhatched young. Sometimes the ovum is found 

 covered by the cotton-like down spun by the mother, 

 but in this case oviposition clearly has occurred. 



The diversity of form and colour shown in these 

 galls is remarkable ; yet it will not be safe to infer 

 that because a gall is constructed on a different portion 

 of a leaf, or is diverse in form or colour, that it neces- 

 sarily proves to be the work of another insect. Never- 

 theless, there is often a distinctive character of nidus- 



