THE GENUS DENDKOCTONUS. 



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. 



The largest and best fig. 53 

 trees are usually at- 

 tacked first, but after 

 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 



The Black Hills beetle: Tree with bark removed, show- 

 ing egg galleries grooved and marked on surface of wood. 

 (Author's illustration.) 



