THE GENUS DENDROCTONTJS. 



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 



