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 7 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 Xew 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 knowm 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 w T as found in the living bark on a red-spruce 
stump in West Virginia, which is all that is known of its habits. 
