GENERIC CLASSIFICATION" OF APHIDIDAE. 65 



Key to the Tribes of 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 pseuclogalls 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-3ecreting areas present but not 

 prominently developed . Alate forms leaving the galls in the la te summer or 



fall. Antennae with annular sensoria Melaphini. 



Forms livdng 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 of 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. 



1 There is considerable evidence for separating a tribe Tetraneurini to include the genera Colopha 

 Tetraneura, and Gobaishia. 



141613°— 20— Bull. 826 5 



