GENERIC CLASSIFICATION OF APHIDIDAE. 39 
It would appear that this tribe separated from the aphid line after 
the cornicles had lost their armature and before their development 
as indicated in the Aphidina and Macrosiphina began. These organs 
then remained somewhat primitive whereas reduction took place in 
the antennae and wings. One genus only is represented. 
Genus SETAPHIS Van der Goot. 
Plate V, Q-X. 
1916. Setaphis Van der Goot, Zur Kenntniss der Blattlause Java's, p. 153. - 
Characters. — Cornicles present as rings, situated on low broad cones. Antennae of 
five segments armed with small circular sensoria. Fore wings with the media once 
branched, hind wings reduced. Cauda and anal plate rounded. Body with two 
prominent caudal fingerlike projections. 
Type (fixed by Van der Goot, 1916), Setaphis luteus V. d. Goot. 
Tribe APHIDINI. 
The tribe Aphidini is by far the largest tribe of the living Aphididae. 
Many of the most common species in the family as well as many 
of the most injurious ones belong here, and it is these forms which 
correspond to the popular conception of the family. 
Besides being abundant they are varied, and a large number of 
genera is therefore found in this tribe. Specialization has taken 
place in a number of directions, but particularly in the development 
of cornicles, cauda, etc. The wings have become somewhat reduced 
in certain genera, but as a rule little reduction in these organs has 
occurred, the venation in most cases being as complete as in even 
the most primitive forms of the family. The antennae have developed 
an elongate filamentous process to the distal segment, which in the 
Lachnini is represented by a very short thumblike projection. Wax 
secretion is found scarcely at all apart from that produced and 
secreted by the cornicles. The head shows certain peculiar develop- 
ments in some of the tribes in that the antennas are situated on 
prominent tubercles variously shaped and armed. 
As a rule the body is more or less naked, being covered only by a 
few scattered hairs. In the peculiar specialized Cervaphidina, 
however, large toothed processes extend outward from the body 
surface. 
Migration between a primary host and one or more secondary 
hosts often occurs. Apterous and alate viviparous forms, therefore, 
are common, but no definite relation exists between them. The 
forms feed mostly upon the leaves of trees and herbs but they may 
also be found feeding upon the twigs and roots. They are not 
infrequently attended by ants. The oviparous females are nearly 
always apterous, but the males, on the other hand, usually are winged. 
Apterous males, however, are common and intermediate forms 
between alate males and apterous males sometimes occur. Inter- 
