GENERIC CLASSIFICATION OF APHIDIDAE. 65 
Key to the Tribes op the Eriosomatinae. 
1. Cornicles present, at least in the alate forms; however, often mere rings 4. 
Cornicles absent 2. 
2. Forms living in true galls or in pseudogalls on plants 3. 
Forms living in the nests of ants or at least subterranean, feeding on the 
roots of plants; wax-secreting areas present; antennae of alate forms rather 
short and thick with somewhat oval sensoria Fordini. 
3. Forms living in true galls and without wax plates prominently developed 
on the head and thorax of alate form; wax-secreting areas present but not 
prominently developed. Alate forms leaving the galls in the late summer or 
fall. Antennae with annular sensoria Melaphini. 
Forms lining in pseudogalls, occasionally in true galls. Antennae of alate 
form rather long and slender, with narrow or somewhat oval or rounded 
sensoria . Wax plates well developed and present on the head and thorax 
of the alate forms which leave the galls in the spring Prociphilini. 
4. Forms living in galls, pseudogalls, or free upon their host; wax glands prom- 
inently developed; antennae of alate forms armed with annular sensoria 
which almost completely encircle the segments Eriosomatini. 
Forms living usually in true galls; wax glands present but not strongly de- 
veloped; antennae of alate forms armed with narrow, transverse sensoria, 
somewhat oval or irregular ones, or occasionally without sensoria. .Pemphigini. 
Tribe ERIOSOMATINI. 
The tribe Eriosomatini is composed of insects which have more 
or less developed the habit of gall formation, which are possessed of 
wax glands, and the antennas of the alate forms of which are armed 
usually with annular sensoria. Their typical host group is that of 
the elms. 
Characters. — Forms living in galls, pseudogalls, or free upon the twigs or roots of 
their host on which they form excrescences. Prominent wax glands present. Cor- 
nicles distinct; antennae of alate forms armed with annular sensoria which often almost 
completely encircle the segments. Sexual forms small, apterous, beakless; oviparous 
females developing a solitary egg. 
Key to the Genera op the Eriosomatini. 
1. "Media of the fore wings of alate form once branched 3. 
Media of the alate form simple 2. 
2. Hind wings with both media and cubitus present Gobaishia. 
Hind wings with only the media present Tetraneura. 1 
3. Hind wings with both media and cubitus present Eriosoma. 
Hind wings with only the media present 4. 
4. Stem mother with four-segmented antennae; antennae of alate form rather 
short and thick Colopha. 
Stem mother with five-segmented antennae ; antennae of alate form long and 
slender. Georgia. 
i There is considerable evidence for separating a tribe Tetraneurini to include the genera Colopha, 
Tetraneura, and Gobaishia. 
141613°— 20— Bull. 826 5 
