TRIBES OF APHIDIDAE 63 
family. Koch (1854) indicated the genus Aphis with several other 
genera as the tribe Aphiden which is a nomen nudum.  Passerini 
(1863) considers it under the subfamily name Aphidinae. Thomas 
(1878) has the term Aphidini in a tribal sense. Mordwilko (1908) 
first used the term Aphidina as a group including the tribes Chaito- 
phorini and Aphidini. 
Morphological characters. Frontal margin between the antennae 
straight or nearly so, or, more commonly, concave, the angles of the 
head being drawn out into frontal tubercles on which the antennae are 
situated. Antennae usually as long as or longer than the body; spur 
always elongated, sometimes exceedingly long. Sensilla of the an- 
tennae are sometimes hair-like, usually spine-like, capitate, or spatu- 
iate. Prothorax and abdomen often with lateral tubercles like those 
found in the Pterocommini. Cornicle cylindrical and long, sometimes 
enlarged or widened. Cauda conspicuous and triangular or pointed. 
Anal plate entire. 
Biological characters. This is the largest group in the family, 
containing something like one half of the species. Their classification 
is correspondingly difficult and has lagged behind the other groups 
which contain a smaller number of forms. The Aphidina contain the 
modern, progressive forms that have taken a prominent place in the 
insect world and are still expanding. While some continue to return 
to woody plants for ovipositing, the majority have become com- 
pletely adapted to live on herbaceous plants. They are all strongly 
gregarious, forming large colonies. 
KEY TO THE TRIBES OF THE APHIDINA 
1. Frontal margin nearly straight, or with broad and shallow coneavities; sen- 
silla of the antennae short, spine-like and sharp pointed; sometimes long and hair- 
like, but never enlarged at apex; third segment of the antennae rarely with sensoria 
IDOE ES PUTA. 10. Tribe APHIDINI 
—Frontal margin usually deeply concave; sensilla of the antennae capitate or 
variously enlarged apically. . . . 2: 
2. Frontal margin narrowly coneave, at least in the apterous and larval forms, 
due to a glandular swelling of the antennal tubercles; sensilla of the antennae usually 
capitate, like those on the front and body in the larval forms. BPD 
11. Tribe MYZINI 
—Frontal margin broadly and deeply concave in the larval as well as in the adult 
forms; sensilla long and spatulate; those of the front, body and in larval forms 
usually hair-like; third segment of the antennae usually with sensoria in the 
Soom, 3 Gg et 12. Tribe MACROSIPHINI 
LOS Ripe Ab HED ENT 
Morphological characters. Frontal margin straight, or with shal- 
iow concavities, the antennae not situated on conspicuous frontal tuber- 
cles. Sensilla of the antennae rarely hair-like as in Chaitophorini, 
