12 BULLETIN 826, U. S. DEPARTMENT OE AGRICULTUKE. 
Tribe LACHNINI. 
The tribe Lachnini is the most primitive of all living aphids, with 
the exception of the Mindarinae. The genus Mindarus shows in its 
wing structure characters more primitive than any of the Lachnini, 
but in other characters such as those of the beak, cornicles, cauda, 
sensory structures, etc., the Lachnini are very primitive insects. In 
examining the fossil wings it is to be noted that the radial sector is 
situated back of the stigma. In practically all living aphids, with the 
exception of Mindarus, this vein has migrated toward the tip of the 
wing. In primitive forms the stigma is long and narrow, whereas in 
most living forms it has become more or less compact. In the subtribe 
Lachnina the radial sector has become a very short, straight vein almost 
at the tip of the wing. This shows that the Lachnina are evidently 
more advanced than the Pterochlorina in which the radial sector is 
somewhat curved and situated near the middle of the stigma. The 
subtribe Eulachnina is considerably specialized, as indicated by the 
eyes, the shape of the body, and the cornicles. It is, however, as 
closely related to the Lachnina as are any of the other tribes, as will 
be seen from the formation of the wing. The Anoecina in the typical 
genus shows a wing with a short blocky stigma, a condition quite 
different from that seen in the Lachnina, and the radial sector is here 
curved. (In Nippolachnus, however, the stigma is still long and 
straight.) Moreover, the sexual forms are more specialized, being 
apterous in both cases. Anoecia, therefore, is somewhat removed 
from Lachnus. The genus Trama is considerably specialized, in 
that it lacks cornicles in the apterous form. It is, however, related 
to Lachnus through Neotrama with small cornicles, and Protrama 
with large hairy cornicles. 
The rostrum in the Lachnini is in many species five-segmented, a 
primitive character most marked in this group. The freshly emerged 
wing of a lachnid shows that M x , M 2 , and M 3+4 are the veins repre- 
sented when the media is twice branched, and that in some species no 
vein is formed about M 2 . The cubitus and first and second anal 
are present in the forewing. As in other Aphididae, however, no 
vein forms about the second anal. The radial sector is in Lachnus 
a short, straight trachea and a prominent vein forms about it. The 
stigma, as in all members of the family, is formed by radius^ In the 
hindwing both media and cubitus are present and form distinct 
veins. 
The antennas of the Lachnini are six-segmented with a short 
unguis. They are usually armed with oval or sub circular sensoria 
and prominent hairs. In fact, the entire body of the insect is hairy. 
The cornicles are characteristic. They are situated on distinct 
cones which are constricted before the somewhat flanged opening 
which is not situated over the center of the cone. The cones are arm- 
