156 THE SCOLYTID BEETLES. 
May and June, and continue activity until hibernation begins in the 
fall. The overwintered broods of large larva? evidently complete their 
development to pupae and adults and emerge by July, while the young 
larvae may not complete their development and emerge until in 
September and October, and some individuals may pass the second 
winter as adults. 
GENERATION. 
The overwintered broods of adults evidently begin to excavate 
galleries and deposit eggs in the period from April to June, depending 
on latitudes and altitudes, and continue their activity as successive 
broods emerge, during June, July, August, and until September, or 
later. The eggs begin to hatch probably within a week or ten days 
after they are deposited. This process continues during Ma}" and 
June or July, until September, or later. The larval development is 
principally during July, August, and September, but continues until 
hibernation begins. The more advanced larvae begin to transform 
to pupae and adults in August, while some of the others continue trans- 
v formation during September and October, until cold weather, when 
larvae of all stages, pupae, and adults are found. 
While it is possible that some of the more advanced broods in the 
warmer localities may emerge in the late summer or early fail, it is 
evident that by far the greater number pass the winter in the bark, 
where they develop and emerge in the following spring and summer. 
The possibility of individuals of the overwintered parent adults, as 
well as of young adults of the overwintered brood, excavating more 
than one gallery, during the season, together with the probability that 
some individuals of a single generation may pass through two or even 
three winters, involves such an overlapping of broods of different 
generations that even with extensive observations it has been impos- 
sible to arrive at any definite conclusions regarding the normal period 
required for the development and emergence of all of the broods of a 
generation. 
HABITS. 
This species prefers to enter the bark of injured or dying trees or 
that of the stumps and logs of those which have been felled, but often 
attacks the perfectly healthy bark on the base and roots of healthy, 
living trees. 
It has been found in practically all of the eastern pines and spruces 
within its range of distribution, and in nearly all of the principal 
western pines, but in none of the western spruces except the white 
spruce in the Black Hills of South Dakota. It is probable that none 
of the species of pine and spruce growing within its range is exempt 
from its attack. We have no records of it in fir (Abies), or in Doug- 
