The Douglas-fir engraver, Scolytus unispinosus Leconte, is a common bark beetle throughout the Pacific Coast and Rocky Mountain Region of North America. Although it occasionally kills young trees (Chamberlin, 1939), it is of minor economic importance, usually confining its attack to tops, limbs and logging slash. In standing timber it acts primarily as a secondary insect, attacking the tops and branches of trees killed or severely weakened by other agents. In the interior of British Columbia it is commonly found in Douglas fir, Pseudotsuga menziesii (Mirb.) Franco, and thus it is of interest as an associate of the Douglas-fir beetle, Dendroctonus pseudotsugae Hopk. Two other bark beetles Pseudohylesinus nebulosus (Leconte) and Scolytus tsugae (Swaine) with similar associations were studied earlier (Walters and McMullen, 1956; McMullen and Atkins, 1959).
CONIFEROUS HOSTS OF THE IPIDAE OF THE PACIFIC COAST AND ROCKY MOUNTAIN REGIONS
