42 BRITISH APHIDES. 



other walnut species. Its bright colouring accords 

 well with its more exposed situation, and may act as a 

 protection from its enemies. From these considera- 

 tions I propose to place it in the above new genus ; 

 and this procedure will be in accordance with Mr. 

 Walker's views on the subject, as set forth in the 

 ' Zoologist,' 2nd series, vol. v, p. 200. 



Genus XX.-LACHNUS,* Illiger. 



KlENLAUSE. BaUMLAUS. PiNE ApHIS. 



nostrum slender, very long, always longer than half 

 of the body, and sometimes considerably longer ; last 

 joints hastate. 



Antennae short, six-jointed, the last joint ends with 

 a nail-like process, which is the representative of the 

 seventh joint of other genera. The first two joints 

 are short and thick ; the third long, as long as the two 

 following taken together ; the fourth, fifth, and sixth 

 joints are equally long. 



Cornicles small, not longer than broad. 



Cauda none, or inconspicuous. 



Legs very long, particularly the hinder pair ; the 

 tibi93 of which, in the oviparous females, are usually 

 dilated. Tarsi biarticulate. 



Wings very long and broad, stigmata long and 

 narrow ; sometimes considerably encroaching on the 

 extension of the costa; stigmatic cells ovate. Cubital 

 veins twice forked. f 



Lower wings with two oblique veins. 



The genus Lachnus comprises some of the largest 



* From Xd^vaiog, woolly, pilose. 



t Kaltenbacli describes the antennEe as six-jointed, whilst Koch counts 

 in them but seven joints ; for he considers the nail as one. The former 

 author says that he has captured both Lachnus agilis and L. fasciatus 

 with their cubital veins but once forked. This tendency to the suppres- 

 sion of a wing-vein would seem to indicate a possible passage between 

 two genera ; or, viewed from the theory of development, it might show 

 that some individuals only have risen to the higher type. 



