Insects Bred from American Larch ed 
Small sections of the bark containing eggs, the time of 
depositing of which was known, were placed in a moist 
chamber for incubation. The incubation period in the 
laboratories was about twelve days. An egg laid at 4 Pp. M. 
March 8 hatched March 20 and others required a similar 
length of time. 
Adults bred in the laboratory and confined in captivity 
with abundance of proper food lived from fourteen to thirty- 
one days, the average being between fourteen and twenty 
days. The male from which the penis had been removed 
lived the longest period of any — thirty-one days. 
The larve burrow between the bark and the sapwood, 
grooving each about equally. The galleries are irregular, 
sometimes becoming rather long and winding, while in other 
cases they are confined to a small area. Very soon after 
hatching the larva makes an opening to the outside through 
the bark. This is always small, never being large enough 
for the passage of the larva’s body, and is used in thrusting 
out the chips or “ sawdust” of the sawyer, the larval mine 
near this opening being kept clear of this material (Fig. 16). 
Often this frass will collect to form piles of considerable size 
under the infested logs, resembling piles of sawdust. Some 
time during the summer the larva carries its mine into the 
sapwood, often for a depth of several inches when the burrow 
is in the trunk. This mine is used as a retiring chamber 
and, on occasion later, as a hibernating chamber and eventu- 
ally as a pupation chamber. The winter may be passed as a 
full-grown larva or as a larva in any stage of its growth. 
The length of the larval life varies quite remarkably from 
one to three years. Normally the larve complete their 
growth and transform to the adult in a single year, but in 
some cases this may be unduly lengthened by several causes. 
Numerous eases have been noted where blown-over balsam 
trees which happened to lie in locations to which the sun 
never has access have contained the same generation of larvee 
for two and even three years. The larval period may also 
be unduly lengthened by other unusual conditions. On two 
separate occasions, once in the Adirondacks (balsam) and 
