102 MISC. PUBLICATION 273, U. 8. DEPT. OF AGRICULTURE 
more detailed descriptions are unnecessary. Since this beetle is less 
ageressive than the western pine beetle, however, control measures 
are seldom required. 
The roundheaded pine beetle (Dendroctonus convexifrons Hopk.) 
attacks ponderosa pine throughout the same range as the south- 
western pine beetle and often in company with it. This species 
usually enters the lower portion of trees previously infested by other 
bark beetles, but is sometimes primary in its attack upon decadent 
or weakened trees. The adults are about one-fourth inch in length 
and are a dark, shiny brown or black. The egg galleries are mostly 
vertical, long, shghtly to markedly sinuous. The larval mines are 
usually in the cambium; pupation may take place either in the 
inner bark or concealed in the outer corky bark. Normally there 
is but one generation a year, and since the emergence is extended 
throughout most of the season there are never any great numbers 
of beetles attacking at any one time. The species is usually second- 
ary and relatively unimportant. 
The Arizona pine beetle (Vendroctonus arizonicus Hopk.) attacks 
and kills ponderosa pine and Arizona pine in central Arizona and 
probably other parts of the Southwest. Its appearance and habits 
are very similar to those of the southwestern pine beetle, and the 
methods of control are the same. 
The Colorado pine beetle (Dendroctonus approximatus Dieta) 
attacks ponderosa, limber, Arizona, Chihuahua, and probably other 
pines in its range from northern Colorado and southern Utah south 
through Arizona and New Mexico. The dark-brown, elongate adults 
are from one-eighth to about one-fifth inch in length. They exca- 
vate a network of long, anastomosing, longitudinal, diagonal, and 
sometimes transverse galleries between the bark and wood of dying, 
felled, or occasionally healthy trees. The brood gaileries are dis- 
tinguished from those of most other species by the fact that the eggs 
are deposited in large niches on the side of the gallery farthest 
from the wood, rather than on. the other sides of the gallery. Its 
work is therefore characterized by the absence of exposed larval 
mines on the inner surface of the bark. There is only one genera- 
tion annually, and as a consequence it is not an aggressive species or 
of economic importance. 
The mountain pine beetle (Dendroctonus monticolae Hopk.) (30) 
is very destructive to forest trees in the high mountains of Cali- 
fornia, Oregon, Washington, western Nevada, Idaho, western Mon- 
tana, northwestern Wyoming, and British Columbia. In many - 
places it has all but wiped out thousands of acres of lodgepole and 
western white pine (fig. 50), taken a heavy toll of valuable sugar 
pine, and attacked and killed ponderosa pines, whitebark pines, and 
other pines, mountain hemlock, and Engelmann spruce. Trees from 
4 or 5 inches in diameter up to those of the largest size may be 
attacked. Attacks are usually heaviest along the main trunk of a 
tree from within a few feet of the ground up to the middle branches 
but may extend from the root collar very nearly to the top and 
into the larger limbs. During endemic infestations there is a tend- 
ency for the beetles to select the weaker, less vigorous trees for 
attack, but no such selection is apparent during epidemic conditions. 
Infested trees are recognized first by pitch tubes on the trunks of 
