THE GENUS DENDROCTONUS. 
81 
with a few long hairs, the striae narrow, and the spaces between quite 
broad and roughened with sparsely placed granules. (See fig. 44.) 
It attacks injured, felled, and healthy silver or western white pine, 
western yellow pine, and lodgepole pine, in Montana, western Wyo- 
ming, Idaho, Oregon, and Washington; it also attacks sugar pine, 
western yellow pine, and lodgepole pine in the mountains of Washing- 
ton, Oregon, and California. It excavates very long, nearly straight to 
slightly, and sometimes strongly, winding egg galleries through the 
inner living bark and grooves the surface of the wood (figs. 45, 46). 
The eggs are placed in approximate groups at short intervals along the 
sides, and the short and broad to long 
and slender larval mines are exposed in 
the inner bark; the larvae transform to 
pupae and adults in separate cells, exposed 
or concealed in the inner bark. This WM^'^^m Kl 
species is sometimes associated with the 
western pine beetle in the same tree, but 
usually it works independently and oc- 
cupies the greater part of the bark on the 
main trunks. Infested trees are first in- 
dicated by pitch tubes and later by the 
fading yellow to reddish foliage. 
SEASONAL HISTORY. 
OVERWINTERING STAGES. 
The winter is passed as larvae, young 
adults, and parent adults, in the inner 
bark of trees attacked the preceding sum- 
mer and fall, the parent adults in the egg 
galleries or ventilating burrows, and the 
broods in the larval mines or pupal cells. 
Fig. 44.— The mountain pine beetle 
(Dendroctonus monticolx): Adult. 
Greatly enlarged. (Author's illus- 
tration.) 
ACTIVITY OF OVERWINTERED BROODS. 
As soon as the weather is favorable in April and May the overwin- 
tered parent adults extend their incompleted egg galleries or excavate 
new ones in the remaining living bark on the dying trees and deposit 
eggs. The overwintered broods of young adults begin to emerge in 
July. The principal period of emergence is in August, but the 
retarded broods continue to come out until September, or later. 
The broods of larvae begin to transform to pupae and adults in April 
and May and continue to do so until September, or later. Some of the 
larvae evidently pass the second winter as matured larvae and adults. 
The broods from eggs deposited by the overwintered parent adults 
evidently develop to adults in July and August. 
89535— Bull. 83, pt. 1—09 7 
