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 flat cones 2. 



Cornicles truncate, or more or less elongate 3. 



2. Cornicles and antennae hairy. Antennae 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. 



