GENERIC CLASSIFICATION" OF APHIDIDAE. 5 



the same type of wing. Therefore this subtribe is considered quite 

 closely related to the subtribe Lachnina but differing from it in 

 specialization of body form, cornicles, and eyes. The other sub- 

 tribes of the Lachnini have quite a different wing structure. While 

 the radial sector has changed its position considerably from that 

 found in the fossils it has not reached the tip of the stigma and is not 

 straight, but much curved. In this regard, therefore, the Pterochlor- 

 ina is perhaps the most primitive subtribe in the Lachnini, although 

 in many respects it is specialized. On the other hand there are two 

 highly specialized subtribes, the Anoecina and the Tramina. It is 

 usually the custom to place the Anoecina with the Pemphigina. Its 

 relations, however, are here. The adult forms are very similar in- 

 deed to the lachnids. The sexual forms, on the other hand, are 

 small and apterous and suggestive of the sexes of the Eriosomatinae, 

 and there is considerable ground for placing the Anoecina there. 

 These sexual forms, however, seem to differ quite distinctly from 

 those of the Eriosomatinae, which are beakless and the oviparous 

 female of which never develops more than one egg. The develop- 

 ment of the stigma shows quite an extreme modification from the 

 long, narrow, primitive stigma. 



Near this same line of development is the rather highly specialized 

 subtribe Tramina. The most marked character of this subtribe is 

 the extreme modification of the hind tarsi. In considering only the 

 genus Trama it might be thought that the tribe should belong with 

 the Eriosomatinae. The species troglodytes has often been figured 

 with cornicles in the apterous form. Specimens from Mordwilko 

 and Schouteden determined as this species lack them and the writer 

 therefore considers Trama as the most specialized genus in the sub- 

 tribe. Another genus represented by radicis Kalt. shows cornicles 

 very large and of a typical Lachnus character. Through this genus, 

 therefore, the subtribe can be placed at once with its relatives in the 

 Lachnini. Apart from the peculiar tibial character this genus is very 

 lachnid-like. 



The next branch from the Aphidinae is the Callipterus branch, 

 which may be considered as arising somewhat later than the Lachnus 

 branch. From this offshoot soon after it arose and before the present 

 genera of the Callipterini appeared the Thelaxini separated. 



This tribe, the old Vacuini, also has usually been placed with the 

 Eriosomatinae. There are some resemblances, it is true; only one 

 egg, for instance, is usually laid by the sexual female. But this is 

 not always the case, for, according to Buckton, more than one egg is 

 sometimes laid. Such a condition shows that the one egg habit is of 

 much more recent development than in the Eriosomatinae. More- 

 over, the sexual female is very different in structure. She is not the 



