THE GENUS DENDROCTONUS. 39 
parts of the broods complete their development and emerge during 
the first season, and the others remain over until the next season, it 
will be a partial development of a seasonal generation. If all of the 
broods develop and emerge within twelve months from the time the 
first eggs were deposited, it is referred to as a complete annual 
generation. 
Hibernation. — The term "hibernation" as here applied relates to 
the period in the seasonal history of the broods from the time general 
activity ceases in the fall until the time it begins again in the spring. 
In southern localities there may be considerable activity (feeding 
and development) of the broods during the warmer days of winter, 
so that hibernation used in this connection does not mean that the 
broods are entirely dormant and inactive, but that for the greater 
part of the time they are. 
Overwintering stages. — The overwintering stages are those of the 
hibernating broods. 
Overwintered broods. — The term "overwintered broods" relates to 
all stages which have passed the winter in the bark of the infested 
trees, whether active or not. It is, therefore, a better term to use 
for the barkbeetles than "hibernated broods." 
Activity of overwintered broods. — By the "activity of overwintered 
broods" is meant the feeding, development, transformation, emer- 
gence, flight, etc., from the time general activity begins in the spring 
among the broods which have overwintered in the bark. This 
activity may extend over several months and overlap the activity 
of broods of one or more generations. The parent adults that attack 
the tree too late in the fall to complete their egg galleries usually con- 
tinue their work of extending the galleries and depositing eggs when 
activity begins the following spring. Some of the parent adults 
that have completed their egg galleries in the fall may also live over 
winter and excavate new galleries when activity begins in the spring. 
The overwintered broods of young adults include those that trans- 
formed to adults before activity ceased in the fall and passed the 
winter in the pupal cells where they transformed. These are usu- 
ally the first to emerge and fly in the spring, but sometimes they 
remain in the bark until the majority of the broods are fully .devel- 
oped. Among the overwintered broods of larvae there may be all 
stages from very young or small larvae to fully developed ones. The 
latter will begin activity by transforming to pupae. The immature 
larvae begin their activity by feeding and extending their larval mines. 
Under normal or favorable conditions, the majority of the immature 
stages of some species will have completed their development and 
transformed to adults before the overwintered young adults in the 
same tree have begun to emerge, so that nearly all of them may 
leave the trees about the same time, but there are always certain trees 
