INSECT ENEMIES OF EASTERN FORESTS 549 
monograph on the classification of sawflies and gave the diagnostic 
characters of this family and a key to the genera. 
Those of our common species, in general, are rather stout-bodied, 
either reddish brown or bluish black, and with the wings more or less 
fuscous. — 
The larvae have the body rather thick set and semicylindrical. with 
venter flattened, widest on abdominal segments 1 to 3, and tapering 
toward the anal end. They are yellowish green or red and usually 
spotted. 
The full-grown larva of Arge pectoralis (Leach) is about 34 inch 
in length; the head is reddish yellow with a black eye spot on each 
side; the abdomen stout, yellowish, with six longitudinal rows of 
black, nearly confluent, spots on the upper portion, a subspiracular 
row of elongated ones on the fleshy projections, and two rows on the 
underside at the bases of the legs; the spiracles are black and the 
thoracic legs, except the bases, concolorous with the body. This saw- 
fly is widely distributed through the northeastern part of the United 
States and the eastern part of Canada. The larvae feed on various 
species of birch, but more commonly on the gray and paper birches. 
This is probably the most common species of the Argidae in the 
Northeastern States and occasionally becomes abundant enough to 
cause defoliation over limited areas. 
The adults emerge during June and July, and the eggs are deposited 
in slits cut into the margin of the leaf by the female. The larvae 
normally complete their growth in 5 or 6 weeks, and may be found 
from July until late in September, depending on the climatic range. 
The cocoons are spun in the litter on the ground, and the winter is 
passed as prepupal larvae within the cocoons. 
A few other species that occasionally attract attention locally in 
the Northeastern States are briefly mentioned below. The life his- 
tory of each is very similar to that of Avge pectoralis. In Arge 
sp. on elm the larvae closely resemble those of A. pectoralis, but can 
be distinguished by the black blotch on the anal segment of the body 
and by their thoracic legs being black on the outer side. In Avge sp. on 
oak the full-grown larva is from 84 to 1 inch in length; the head and 
base of the thoracic legs are blackish; and the body is yellowish green 
with tuberculate spots and blotch on the anal segment yellowish. In 
Arge sp. on willow, the full-grown larva has a dark brown or blackish 
head, the outer sides of the thoracic legs are blackish, and the venter 
is speckled with black dots; otherwise the markings are similar to 
those of A. pectoralis. 
Arge coccinea (F.) feeds on sumac. The full-grown larva is about 
34 inch in length. It has a black head, the outer side of the thoracic 
legs is black, the body is brick red, and each segment except the last 
has a transverse row of blackish tuberculate spots. There is a black 
spot on the back between the prothorax and the mesothorax and 
another between the mesothorax and the metathorax, and the anal plate 
is blackish. 
Arge humeralis (Beauv.) feeds on poison ivy and poison sumac. 
The full-grown larva is about 34 inch in length. The head is yellow- 
ish red, the body brick red and marked with a double longitudinal row 
of black tuberculate, nearly confluent spots on the back, and a single 
row on each side. There are also a reddish spiracular and a sub- 
