16 
basal joints are very short and subequal in length; the first joint is 
eylindrical and obliquely truncate at the apex, while the second joint 
is almost globular. Joint three is very long in comparison to the two 
basal joints and five or six times as long as either of them. It is of 
uniform diameter and bluntly rounded at the apex, where it bears 
two or three short hairs, and deeply divided by thirty to thirty-six 
more or less regular or complete annulations, without a trace of divi- 
sions into separate joints. The legs are slender and almost destitute 
ot hairs, which are somewhat more numerous and spine-like toward 
the end of the posterior tibiz. There are four slender, subequal, and 
capitate digitules on each tarsus. Stigma long, narrow, lanceolate, 
and as broad as the costal cell, its basal angle almost obsolete. Veins 
simple; the second discoidal arises in front or beyond the middle of 
the first discoidal vein, though occasionally both start from the same 
point. The basal third or more of the third discoidal is obliterated. 
Stigmal vein short and almost straight. In the hind wings the second 
discoidal is generally wanting, frequently a stump of it or the entire 
vein may be observed arising from the first; sometimes both may 
start from the same point, though in rare cases both are normal, 
arising some distance from each other, and almost parallel to each 
other. The head is slightly convex in front. The rostrum is short, 
reaching but slightly beyond the anterior coxe. Tail small, knob- 
like, bearing six to eight short hairs; last abdominal segment bilobed, 
each lobe provided with five or six hairs. There is also a small, 
blackish tuberele each side of the anterior four segments of the 
abdomen. 
After feeding for some time on the juices of the gall, in order to 
become fully mature and strong enough for migration, and also to 
hasten the development of the embryonic larvae, they abandon their 
old home in search for the appropriate food plant for their progeny, 
to insure the perpetuation of their race. Each of these migrants con- 
tains about fifty larvee, which, after reaching the birches, are deposited 
on the under side of the leaves; on reaching the birches they deposit 
from six to eight larvee each day until their stock of larvee is exhausted, 
after which they shrivel up and die. 
Third generation, first stage (Fig. 6).—Young larve of this gen- 
eration were first observed during the first days of June and the first 
mature and apterous females on the 18th of the same month, the 
insects accomplishing all their changes within fourteen days. The 
young larvee are at first of a pale yellowish color, but soon change to 
a brownish yellow; the eyes are dark purplish and the antenne and 
legs colorless. The young larve are very small, barely 0.2™™ in 
length and broadly oval; the abdomen is comparatively small in pro- 
portion to the size of the larvee and only about one-third the length 
of the entire insect. The entire margin of the body is studded with 
short and stout secretory tubercles; sixteen of which are along the 
