GENEKIC CLASSIFICATION OF APHIDIDAE. 11 
possesses an elongate narrow unguis, which in some of the Callipterini 
and Aphidini is remarkably developed. In the more primitive 
groups, however, this is short and thumb-Like. The head of the 
apterous form differs much from that seen in the Eriosomatinae, in 
that true compound eyes are present and often very prominent, and 
the small larval eyes are seen as ocular tubercles. It is noteworthy 
that in the Eriosomatinae the alate forms possess distinct compound 
eyes but the apterous forms have lost them. The wings are in 
general quite similar throughout the family in regard to the venation. 
In color, shape, and location of the veins there is often considerable 
difference. Moreover, there are a few genera amongst the different 
tribes which show abnormal wing form, of which genera Microparsus 
is a good example. In the typical forms of this subfamily the media 
of the fore wing is twice branched, but it is very commonly branched 
only once and it is rarely simple. 
The cornicles show remarkable variation. In some forms of the 
Callipterini they are short and slightly swollen at the base, in the 
Lachnini they are low broad cones, whereas in the Greenideini they are 
cylindrical and sometimes longer than the body. Between these 
extremes every gradation occurs. The cornicles may be straight or 
they may be swollen to a greater or less degree. Practically all forms 
eject a colored wax from these organs when disturbed. 
The cauda shows almost as much variation as the cornicles, some- 
times being short and rounded, in other cases elongate, spatulate, 
or conical, and in others distinctly knobbed. Variation also is met 
with in the anal plate, though this usually is rounded, In the Callip- 
terini, however, it is often bilobed. 
The tribes of the subfamily may be separated as follows: 
Key to the Tribes of the Aphidinae. 
1. Cornicles situated on broad fiat cones 2. 
Cornicles truncate, or more or less elongate 3. 
2. Cornicles and antennae hairy. Antennas with the unguis short and thick. . 
Lachnini. 
Cornicles and antennae not hairy. Antennae with the unguis long and 
slender Setaphidini. 
3. Cornicles clothed with long hairs .Greenideini. 
Cornicles never with long hairs 4. 
4. Thorax of alate form with the lobes not prominently developed; oviparous 
form small, often laying one egg. Large wax plates present Thelaxini. 
Thorax of alate form with the lobes prominently developed; oviparous 
female laying several eggs. Large wax plates usually absent 5. 
5. Cornicles truncate or elongate; when elongate the cauda knobbed, and the 
anal plate bilobed, or the antennae prominently hairy Callipterini. 
Cornicles not truncate, usually elongate. Cauda never knobbed. Anten- 
nae with only a few spinelike hairs Aphidini. 
