TRIBES OF APHIDIDAE 57 
KEY TO THE TRIBES OF THE CHAITOPHORINA 
1. Cornicles usually longer than broad and enlarged in the middle; size large. 
Found feeding on woody parts of trees. . . . 3. Tribe PTEROCOMMINI 
—Cornicles short and truneate; size smaller. Found feeding on leaves of 
TLEGS ES a" 2. 
2. Antennae of six segments. .. . 4. Tribe CHAITOPHORINI 
—Antennae of five segments. . . . 5. Tribe VACUNINI 
3. Trre PTEROCOMMINI 
Koch, 1857. Die Pflanzenl. Heft 8. Sub Cladobius (Phyllaphiden). 
Passerini, 1860. Gli Afidi. Sub Aphioides (pro Cladobius). 
Buckton, 1879. Monogr. Vol. 2. Sub Melanoxanthus et Pterocomma. 
Mordwilko, 1894. Uniy. Warsch. Sub Symdobits. 
Pergande, 1900. Proce. Wash. Acad. Sci. Vol. 2. Sub Cladobius (Koch) Perg. 
Kirkaldy, 1905. Canad. Entom. Vol. 37. Sub Aristaphis (pro Cladobius). 
Schoutenden, 1906. Mem. Belg. Vol. 12. Sub Melanoxantherium (pro Melanoxanthus). 
Wilson, 1912. Canad. Entom. Vol. 42. Sub Pterocommini (tribe). 
The Pterocommini have only lately been recognized as a distinct 
tribe. Koch (1857) erected the genus Cladobius, the first generic dis- 
tinction of the tribe. Passerini (1860) changed this to Aphioides as 
Cladobius was preoccupied. Buckton (1879) proposed two new 
genera, Melanoxanthus and Pterocomma, the second of which is now 
known to be the same as Koch’s Cladobius and replaces this as Pas- 
serini’s Aphioides also proves to be preoccupied. Mordwilko (1894) 
erected the genus Symdobius which is closely related to the present 
tribe. Pergande (1900) considers the American forms under Koch’s 
term Cladobius in a somewhat enlarged sense. Kirkaldy (1905) makes 
a third attempt to replace the preoccupied term Cladobius under the 
name Aristaphis. Schouteden (1906) proposed Melanoxantherium 
to replace Melanoxanthus which also proves to be preoccupied. Wil- 
son (1910) first recognized the tribe Pterocommini. 
Morphological characters. Rostrum moderately long, but shorter 
than in the Lachnina. Antennae variable in length, usually shorter 
than the body, rarely as long as the body; terminal segment short and 
with a short but distinct spur; marginal sensoria sometimes scattered 
but more often grouped close together. Wings large and venation typi- 
cal, veins sometimes with dusky bands. Abdomen usually with dis- 
unct lateral tubercles, a character sharply marked in the present tribe 
and again in the Aphidini; the significance of these organs is not 
known. Cornicles longer than broad and widest in the middle; rarely 
cylindrical, reduced or wanting. Cauda short and broad. 
Biological characters. In size the present tribe includes all the 
iarger forms of the group; all are bark feeders on woody parts of 
trees and in exceptional cases on roots. Body with long hairs and of 
