THE GENUS DENDKOCTONUS. 



85 



where only the top or one side of a tree was killed the first year, or 

 when living bark remains toward the base, which is attacked the 

 second year by the overwintered parent adults and young adults 

 from the overwintered broods. But it is safe to conclude that after 

 the leaves are all dead and brown, very few representatives of the 

 broods will be found in the bark. 



Fig. 47.— Silver or western white pine killed by the mountain pine beetle in the Priest River National 



Forest, Idaho. (Original.) 



EFFECTS ON COMMERCIAL VALUE OF THE WOOD. 



The commercial value of the silver pine, sugar pine, and lodgepole 

 pine, owing to the thin sapwood, is often not seriously impaired for 

 many years after the trees die, provided they are not injured by fire, 

 storms, wood-boring grubs, and premature decay. The yellow pine, 

 with its thick sapwood, suffers immediate deterioration owing to the 

 bluing fungus which follows the attack of the beetles, causing the 



