16 THE SCOLYTID BEETLES. 



Species 3, 5, and 8 are usually associated with No. 2 in the western 

 yellow pine, but none of them has been especially destructive, al- 

 though independently or collectively they are capable of being so. 

 Species 4 attacks all of the pines and spruces within its range, and 

 while it caused widespread devastation in its northern range during 

 1891 and 1892 its destruction of timber within its southern range, 

 so far as observed, is comparatively moderate. 



The species of subdivision B are the most destructive insect enemies 

 of western pine forests. Species 9 attacks the western white pine, 

 silver pine, sugar pine, lodgepole pine, and western yellow pine, and 

 is exceedingly destructive in certain localities throughout its range, 

 especially to the silver pine, sugar pine, and lodgepole pine. Species 

 10 attacks the Rocky Mountain variety of the western yellow pine, 

 limber pine, white spruce, and Engelmann spruce, but confines 

 itself principally to the yellow pine and is exceedingly destructive, 

 as has been conclusively demonstrated in the Black Hills Forest 

 Reserve of South Dakota and in numerous localities in Colorado. 

 Species 11 attacks the Jeffrey pine and western yellow pine, but 

 principally the former, to which it is quite destructive. 



The species of Division II attack pines, spruces, larches, and 

 Douglas fir, and some of the species are very destructive to living 

 timber. 



Species 12 confines its attack to the eastern larch. There is no 

 positive evidence that it is primarily destructive to living timber, 

 but it evidently contributes to the death of trees defoliated by the 

 larch worm. Species 13 confines its attack principally to the Douglas 

 fir, but is also found in the bigcone spruce and western larch. In 

 the northwestern section of its range this species is not especially 

 destructive, but in its eastern and southern range it is very destruc- 

 tive to the Douglas fir. 



Species 14 attacks the red spruce, black spruce, and white spruce, 

 and from time to time during the past century it has been exceed- 

 ingly destructive to the red spruce in Maine and New Brunswick. 

 Species 15 attacks the Engelmann and evidently the other spruces of 

 the Rocky Mountain region. There is conclusive evidence that it 

 has caused widespread devastation of matured spruce during the 

 past fifty years, and it is now quite aggressive in some localities. 

 Species 16 has been found in the white spruce, but nothing more is 

 known of its habits. Species 17 attacks the Sitka spruce, but there 

 are no records to indicate that it has been primarily destructive to 

 living timber. Species 18 lives in the white pine, but nothing further 

 is known of its habits. Species 19 attacks living lodgepole pine and 

 Engelmann spruce, but it is not known whether or not it is primarily 

 destructive. Species 20 was found in the living bark on a red-spruce 

 stump in West Virginia, which is all that is known of its habits. 



