123 
The Egg. — Our earliest date for the eggs is May 22 (1903), 
and they have been found in twigs of the ehn and the other trees in- 
fested, at frequent intervals from that date to June 24. As the 
girdling of twigs was at its height May 29, 1903, and has been no- 
ticed as late as June 10, it is probable that oviposition may con- 
tinue at least to the latter date. 
The Larva. — The larvae of the preceding year are found in the 
stubs of twigs on the trees in spring, but, according to our obser- 
vations, all have pupated and emerged, as a rule, before the young 
of the following brood begin to hatch. Our earliest date for the 
hatching of the larvae is June 13, and the latest is about the 24th 
of June. The average length at the latter date is about a sixth of 
an inch, which is nearly a third the length of the full-grown larva. 
July 21, 1905, thirteen young larvae measured from 4 to 11.5 mm. 
(.16 to .46 of an inch), with an average of 7 mm. (.28 of an inch), 
varying, that is, from one third size to nearly full grown, and aver- 
aging about half their final length. The burrows of several speci- 
mens varied in length, at this time, from i inch to 25^ inches. 
According to the observations of Mr. Titus, the young larva, 
upon first breaking the shell of the Qgg, begins immediately to gnaw 
a channel downward just beneath the bark, and turns inwards 
towards the center when it is about half way out of the shell. When 
it has thus freed itself from the o^gg it apparently backs up into the 
shell cavity and cuts a small circular hole in the bark as a vent for 
its excrement, which, up to this time, has been left in the cavity 
originally containing the tgg. It then burrows down the center of 
the twig, making additional holes to the surface from one to two 
inches apart as it progresses. 
In small twigs, almost the whole interior is thus eaten out 
(PI. VIII., Fig. &.), leaving only the shriveled bark and a very thin 
layer of wood ; and occasionally this inner cavity reaches nearly to 
the truncated tip of the twig, as if the borer had worked first in a 
direction opposite to its usual course. From the progress of a larva 
down its twig, it appeared that its average rate from June 23 to 
August 31 was a little less than a fifth of an inch a day (4^4 mm.), 
but water-sprouts nearly two feet long were seen in September hol- 
lowed out to the base by a single larva. When a burrow passes the 
point of origin of a lateral twig, the base of this is sometimes eaten 
out and used as a place of deposit for the larval excrement. Some- 
times twigs passed by the larva in its dow-nward descent are suc- 
cessively cut off from within, the insect eating a circular groove 
through the wood, so weakening the twig that it presently breaks 
