GENEKIC 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 
