GENERIC CLASSIFICATION OF APHIDIDAE. t 
and the other toward the development of them. The first subtribe, 
the Monaphidina, lacks cornicles above. The second of these two, 
the Drepanaphidina, possesses them in varying degrees. In this last 
subtribe the males are winged, and the females have developed an 
extremely long, narrow ovipositor. 
Coming now to that line represented by Chaitophorus, the Chai- 
tophorina are found to be the most generalized, corresponding quite 
closely with the Callipterina. In this subtribe males are winged as a 
rule, but sometimes in the same species they are intermediate or 
apterous. Arising from the same branch with the Chaitophorina 
are two subtribes specialized in different directions, like the sub- 
tribes of Callipterus. The first, Fullawayina, lacks cornicles entirely, 
whereas the Pterocommina has developed them in varying degrees, 
as has the Drepanaphidina. This concludes the subtribes of the 
Callipterus branch. 
In connection with these insects the tribe Greenideini should be 
considered. The cornicles of the primitive aphids were evidently 
small, somewhat rounded or conical, and armed with hairs. In the 
Greenideini the insects have very long cylindric or somewhat swollen 
cornicles which are thickly covered with prominent hairs. No such 
well-developed cornicles are met with in any of the other tribes of the 
family, although they are approached in the Macrosiphina. In this 
latter subtribe species occasionally occur which show a few short hairs 
on the cornicles. It seems evident then that the Greenideini separated 
from the Aphidinae before the hairs of the cornicles disappeared. 
This was evidently more recent than the development of the tribe 
Lachnini which possesses a much more primitive cornicle. At about 
the same time that the ancestors of the Caliipterini separated from 
the Aphidinae, other forms probably separated and more or less 
paralleled in some ways the ancestors of the Macrosiphina, but unlike 
them carried the hairs of the cornicles. They thus resulted in forms 
with very long cornicles similar to those of the Macrosiphina but 
armed with long hairs. In other characters, too, they of course differ, 
particularly in regard to the cauda. 
In considering the further development of the Aphidinae, a more 
or less distinct development of the cornicles and antennal tubercles is 
found. There are thus two types which separate themselves, rep- 
resented by Aphis and Macrosiphum respectively. These may be 
considered as leaving the aphid line at about the same time after the 
development of prominent cornicles. There are, consequently, two 
subtribes, the Aphidina and the Macrosiphina. The Cervaphidina 
represents a group of insects armed with long, somewhat cylindric 
cornicles, and very prominent spinelike protuberances. The number 
of antennal segments is somewhat reduced, as is also the wing vena- 
tion. It seems evident then that this is a subtribe on somewhat the 
