TriBes OF APHIDIDAE 55 
readily separated from the preceding by structural as well as biological 
characters. 
Morphological characters. Antennae six-jointed. Rostrum some- 
what shorter and stouter than in Lachnini; apparently four-jointed ; 
some forms of the tribe are provided with an exceptionally long 
rostrum, much longer than the body, which is evidently an adaptation 
and of secondary value. Wings usually long with distinct venation ; 
the stigma elongated and coming to a point at the apex, rarely approach- 
ing the truncate ; forms with short wings have a short and broad stigma ; 
stigmal vein takes its origin some distance back of the apex of the 
stigma and runs as a straight vein to the margin of the wing except 
for a short curve close to its origin. Forms with short stigma have 
a strongly curved stigmal vein. The media is twice branched and 
appears as a stronger vein than in the Lachnini. 
Biological characters. The Pterochlorini are among the largest 
of our aphids, with exceptionally long hind legs. The group is found 
as bark feeders on the trunk and limbs of deciduous trees and other 
woody plants; more rarely underground near the base of the trunk 
or on roots. They are usually found in more exposed places than the 
shade loving Lachnini; they are, therefore, more highly colored, the 
wings often with dusky bands along the veins and with dusky spots. 
In their essential characters they show a close relationship with the 
Lachnini. 
II. Group CHAITOPHORINA 
Koch, 1854-1857. Die Pflanzenl. Sub Aphiden, Phyllaphiden, et Vacuniden. 
Passerini, 1863. Aphid. Ital. Sub Aphidinae, Lachninae et Chermisinae. 
Buckton, 1876-83. Monogr. Sub Aphidinae et Pemphiginae. 
Thomas, 1879. Report 8. Sub Aphidini Lachnini et Pemphiginae. 
Oestlund, 1887. Bull. 4. Sub Callipterini. 
DelGuercio, 1900. Nuoy. Relaz. Vol. 2. Sub Aphidinae et Myzoxylinae. 
Mordwilko, 1907-8. Acad. Imper. Vol. 18. Sub Aphidina, Callipterina et Pem- 
phiginae. 
Wilson, 1910. Canad. Entom. Vol. 42. Sub Callipterinae. 
The genera of the present group have for a long time been dis- 
tributed under the various groups or tribes of the Aphidina, Lachnina, 
Callipterina and Pemphiginae and only recently have they been united 
under a common name. Koch (1854) first established the genus 
Chaitophorus under his Aphiden, other related genera were placed 
by Koch in the Phyllaphiden and Vacuniden. Passerini (1863) placed 
most of the genera in the Aphidinae, except that Sipha was placed in 
the Lachninae, and Vacuna with the Chermesinae. Buckton (1876- 
1883) distributed the genera treated in part under Aphidinae and in 
