8 BULLETIN 826, U. S. DEPARTMENT OF AGRICULTURE. 
sanie line of development as the Aphidina but developing these spec- 
ialized spines during the same period in which the wings and antennae 
have become reduced. Still another subtribe, the Pentalonina, 
shows a very peculiar wing venation. This is not so much a primitive 
wing as a more specialized one. It is placed, therefore, as one of the 
highest subtribes of the Aphidini. 
There remains yet for discussion the tribe Setapmdini. This, it 
seems evident, belongs with the Aphidinae. In regard to the an- 
tennae and the wings it is quite highly specialized but in regard to the 
cornicles, cauda, and anal plate this statement can not be made. The 
natural position of this tribe is somewhat doubtful. Its ancestors 
evidently separated from the aphidian line before the prominent corn- 
icles of the Aphidina, Macrosiphina, etc., appeared and yet the species 
are more specialized in many ways than are members of those sub- 
tribes. It would appear that the lines separated after that of the 
Greenideini, for the cornicles are not hairy. Yet this separation must 
have taken place a considerable time before that of the AjDhichna and 
Macrosiphina. The tribe is placed, therefore, as indicated in the 
diagram (fig. 1). 
The subfamilies, other than the Aphidinae, include the most spec- 
ialized members of the family. By far the most primitive of these 
subfamilies is the Mindarinae. This subfamily, as has been in cheated, 
is a remnant from the past, giving some idea of the ancestors of the 
Eriosomatinae and the Hormaphidinae. The wing structure is partic- 
ularly worthy of study. The wing of no other living aphid is like it, 
but this peculiar structure is abundantly met with in fossil forms. 
The media, it is true, is more reduced than in certain members of the 
Aphidinae, but this is of very little importance as compared with the 
wing's peculiar structure. The form also feeds upon conifers and this 
is. undoubtedly a primitive habit. The cauda and anal plate are 
unlike those met with either in the Eriosomatinae or the Hormaph- 
idinae. 
The sexual forms are interesting. They have become sufficiently 
specialized toward the Eriosomatinae to have lost the wings, but they 
retain the beak, at least in most individuals, and feed. The ovaries 
of the oviparous female also are developed so that a number of eggs 
are laid. 
The two remaining subfamilies are the most highly specialized of all 
aphids. 
The Eriosomatinae are in many ways more specialized than the 
Hormaphidinae, but in other ways they are more primitive. The 
whole Eriosoma line separates at once on the sexual forms. These 
are small, apterous, and beakless. Throughout their life they take 
no nourishment, and the ovaries of the oviparous female become 
atrophied, so that only one develops and of the eggs therein only one 
