THE GENUS DENDROCTONUS. 
43 
The broods of young adults in the pupal cells begin to emerge from 
the trees about the last of June, and continue to come out until the 
middle or last of August. The broods of overwintered larvae begin 
to transform to pupae about the middle of April and to adults toward 
the last of April, and the latter begin to emerge from the trees about 
the middle to last of July, so that practically all of them are out by 
the last of August, although some of the retarded ones continue to 
emerge until September or later. 
Fig. 7.— The western pine beetle: Egg galleries. Reduced. (Author's illustration.) 
FIRST GENERATION. 
The overwintered broods of adults begin to attack the trees, exca 
vate galleries, and deposit eggs about the first of July, and continue 
their activities until September or later. The principal period of 
attack is during July. 
The larvae begin to hatch in from four to ten days after the eggs 
are deposited, and may be found in the bark of the same tree from 
early in July until October, but the principal development is during 
July and up to the middle of August. They begin to transform to 
