4 BULLETIN c 26. U. S. DEPARTMENT: OS AGBICOI/FUBE. 
nam— here used: Aphidinae. Eriosoinatinae. and Hormaphidinae. 
Besides these there is the one species, in sonie ways a relic of the 
past, forming the Mindarinae. 
As will be seen by the diagram 6g. 1 . the Aphidinae is considered 
the most primitive subfamily of the three main groups. This is 
substantiated by the habits of the insects, by the structure of the 
wings, beak. etc.. and by the sexual forms. 
Practically all of these insects are foliage or twig feeders. They 
live, as a rule, in colonies and have not developed any very 
methods of life, such as highly complex gall formation. With the 
exception of the Mindarinae the most primitive wing structure oc- 
curring in the family is met with here. The media is most commonly 
e branched throughout the subfamily and even in the Mindarinae 
there is more of a reduction thou this. The antennae are oi 
segm : :-. the largest number found in the family, and the sen- 
soria are simpler in nam; those met with in the other b 
sul families. The beak in the Lachnini shows also a primitive 
condition in its segmentation. 
The sexual forms are most primitive in the Aphidinae. Winged 
sexes often oc m at] ast the males are very < n ged. Both 
sexes still ret their 1 eaks and feed on their hosts in the same 
th )thei forms, and the ovaries oi the female develop 
normally, and she produces several eggs. 
When the phylogeny of this subfamily is studied, there becomes 
evident the primitive character retained by the Lachnini. In these 
forms the beak structure and the nature of the antennae and 
cornicles point to a primitive <:■■ ndition. The sexes, too. indicate 
this though not markedly more than in other tribes. But the fact 
: these forms are mostly conifer feeders should not be overlooked. 
It is the opinion of the writer that this is a primitive hs 
The Lachnus branch] therefore, may be considered the lowest branch 
: the Aphidinae. If the wings :i fossil aphids b< examined it 
will be seen that by far fche great i i : them possess a wing 
ture quite different from that of out living forms. The radial 
r arises back of tl aa, which is usually very long and narrow. 
is retained probably only in the Mindarinae. It is 
evident, then, that during the development of the present Aphidinae 
this vein migrated toward the tip of the wing until it came to stand 
i middle I stigma or near its tip. On one line of 
Lachnina wherein the vein has reached nearly 
to t bag nd become short and straight. The rem 
. _ acters apart from the wings have in these forms remained 
quite primitive. The sub tribe Eulachnina is evidently a more 
specialized group on this same line of development, for it possesses 
