82 
THE SCOLYTID BEETLES. 
GENERATION. 
The overwintered broods of adults begin to attack the trees, exca- 
vate galleries, and deposit eggs about the first of August and continue 
to do so during August and September, until October or later, but the 
principal period of attack is in August. The larvae begin to hatch 
early in August and begin to transform to pupa? and adults in Septem- 
ber and October. Under favorable conditions a few adults may 
emerge late in the fall, but evidently it is the normal habit for the 
Fig. 45.— The mountain pine beetle: Egg galleries and larval mines in bark. 
(Author's illustration.) 
Reduced. 
broods of this generation to pass the winter as all stages of larvae, as 
adults in pupal cases, and as parent adults, and it is evident that some 
individuals of the delayed broods do not complete their development 
until in the fall of the year following and that some of them pass the 
second winter as parent and young adults. There is, therefore, but 
one generation annually, with a possible overlapping of the generations 
of three years during the summer. 
