1Q2 MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



more detailed descriptions are unnecessary. Since this beetle is less 

 aggressive 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, slightly 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 {B endro<itonus 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 {Dendroetonus apfrowimatus Dietz*) 

 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 galleries 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 



