THE GENUS DENDROCTONUS. 
93 
activity of the larvae is during the latter part of August, but they 
continue active until the beginning of hibernation in the fall. The 
larvae of a few of the most advanced broods may begin to transform 
to pupae and adults toward the last of September and in October, 
but by far the greater number overwinters in different stages of larvae 
with the parent adults. There is, therefore, but one generation 
each year. It is evident, 
however, that some re- 
tarded individuals from 
the preceding generation 
may pass the second win- 
ter as young and parent 
adults. Thus, during 
the early summer there 
may be an overlapping 
of representatives of two 
and even three annual 
generations. 
HABITS. 
This species appar- 
ently prefers to attack 
living timber, but will 
breed to a very limited 
extent in injured and 
felled trees. It infests 
at least four species of 
pine and two species of 
spruce, and will doubt- 
less attack other pines 
and spruces (except the 
"Douglas spruce") 
growing within its range. 
It prefers the western 
yellow pine, or bull pine. 
Ine largest and best Fig. 53.— The Black Hills beetle: Tree with bark removed, show- 
trees are USUallv at- in & eg £ galleries grooved and marked on surface of wood. 
, , n , . (Author's illustration.) 
tacked tirst, but- arter 
these are killed it will attack and kill the medium to small trees and 
even saplings 8 or 10 feet high or only a few inches in diameter. 
The parent adults excavate their long, nearly straight, longi- 
tudinal egg galleries in great numbers through the inner bark, where 
they often closely parallel each other. The larvae excavate short 
and broad or long food burrows at right or oblique angles to the 
egg galleries through the intervening bark, and transform to pupae 
