108 THE SCOLYTID BEETLES. 
GENERATION. 
The~ overwintered broods of adults begin to attack the trees, 
excavate new galleries, and deposit eggs about the middle of April. 
The principal attack is during April, May, and June, but may con- 
tinue into July or later. The eggs begin to hatch soon after they 
are deposited, and the larvae begin to feed and continue to develop 
during May, June, and July, into August or later, some retarded 
individuals continuing to feed until cold weather. They begin to 
transform to pupae and adults during the latter part of July and 
continue their transformations during August until hibernation 
begins. There is some evidence that a few of the more advanced 
broods may emerge during September and October and deposit 
eggs for the second generation during September and October, but 
it is probable that these late-emerging broods are in the majority of 
cases those developed from overwintered broods of young larvae or 
from eggs deposited in the spring by overwintered parent adults. 
It is very evident, however, that there is quite a complete develop- 
ment of the first generation before the first of October, which accounts 
for the passing of the winter principally as fully developed adults. 
HABITS. 
This species prefers to infest the stumps and logs of felled trees, 
and injured and dying standing ones, in which it breeds in great 
numbers, but in some localities and under favorable conditions it 
will attack healthy living trees and cause their death. So far as 
known, it breeds exclusively in the Douglas fir, bigcone spruce, and 
western larch. The trunks of standing trees from a foot in diameter 
to the large older ones are attacked from the ground to the middle 
portion of the trunk, and sometimes to the lower branches. The 
stumps, logs, tops, and larger branches of felled trees are favorite 
breeding places and are usually thickly infested. 
The parent adults enter from the crevices and depressions in the 
bark, excavate entrance burrows through the outer and inner 
bark, and then extend their long, longitudinal egg galleries through 
the inner living or dying bark. As the gallery is extended, the female 
places her eggs in alternate groups along the sides, and when one 
gallery is completed she either remains in the gallery until she dies or 
leaves it to excavate a new one. The larvae, upon hatching, begin to 
feed on the inner bark and to extend their food burrows at right or 
oblique angles to the mother gallery. Instead of the burrows being 
short and broad like those made by many other species, they are 
often extended to a length equaling or exceeding that of the mother 
gallery, and cross each other in such a manner as to completely 
girdle the tree and separate the bark so that it is easily removed from 
