6 BULLETIN 826, U. S. DEPAKTZtfEXT OE AGRICTLTTEE. 
degenerate, beakless. nonfeeding indiTidual of tlie Eriosomatinae. but 
feeds upon the leaf like the viviparous forms. Moreover, in external 
structure these insects resemble certain ones of the Callipterini, to 
such an extent, indeed, that Davidson has described one of these 
forms as a Chaitophorus. Certain of the structures met with in these 
forms resemble those found in the Hormaphidinae and on these 
structures the tribe might be placed there. The writer believes, 
however, that the true affinities of the tribe are shown by comparison 
with the Phyllaphidina. It will be seen at a glance that there is a 
very close resemblance in all main characters. But the sexual forms 
are clirlerent. although not so strikingly different as would appear at 
first. In the Phyllaphidina both winged and wingless ovipara and 
as a rule winged males occur. But in some species (quercifoliae) 
intermediate and apterous males also occur. It is not a very long 
call, therefore, from "the apterous males and females of the Phyl- 
laphidina to the apterous sexes of the Thelaxini. But the habit of 
ego; laving met with in this last tribe shows that it has been on this 
course of development longer than has the Phyllaphidina. The 
group is therefore considered as a tribe which has separated some- 
what earlier and yet has paralleled in some ways certain characters 
of the Phyllaphidina. 
Continuing with the Callipterus branch we find two somewhat 
similar lines of development, the one represented by the Calhpterina 
and the other represented by the Chaitophorina. Both are similar 
in many regards, but are quite different in the armature, particularly 
of the antennae. 
The first subtribe separating from that offshoot represented by 
the Cailipterina is the Phyllaphidina. This seems evident from the 
fact that the oviparous forms of some species are yet alate. a primi- 
tive condition found very seldom in the Aphididae. The next off- 
shoot resulted in the Cailipterina where the oviparous forms are apter- 
ous, the cornicles of moderate development, and the wing veins 
usually not reduced. From this offshoot the Saltusaphidina evi- 
dently arose. This little subtribe is closely related to the Calhp- 
terina in many ways, but there are some new developments. In 
the first place the power of leaping has become developed by the 
enlarging of the femora. Secondly, both the sexual forms have lost 
their wings, which the male usually retains in the Cailipterina. One 
of the most important points, however, is the fact that in the Sal- 
tusaphidina the ocular tubercles which represent the retained larval 
eyes are absent, whereas they are quite conspicuous in the Cailip- 
terina. 
On this same Callipterus branch, but somewhat more specialized 
than the Cailipterina, are two subtribes. These have specialized 
in opposite directions, the one toward the elimination of the cornicles 
