166 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



gelmann spruce. It makes a short longitudinal egg gallery with 

 one branch above and one below a central nuptial chamber. 



Several secondary species of very small bark beetles may be 

 found breeding abundantly in dying spruce along with the more 

 primary tree-killing species, usually with their egg tunnels start- 

 ing from those of Ips or Dendroctonus. Crypturgus borealis Sw. 

 is a small brownish beetle about y 1G inch long that breeds abund- 

 antly in spruces, larch, some firs, and western white pine in the 

 Rocky Mountain region and on the Pacific slope. Dolurgus pumilus 

 (Mann.) is about the same size and does similar work in spruce 

 and western white pine along the Pacific slope from Alaska to 

 southern California. Scierus amiectens Lee, a small reddish-brown 

 beetle about y 8 inch long, breeds in white and Engelmann spruces, 

 lodgepole pine, and probably in Sitka spruce in western Canada, 

 the Northwest, and the Rocky Mountain States. 



The four-eyed spruce bark beetle (Pohjgraphus rufipennis 

 (Kby.)) is a common secondary species which breeds in the dead 

 and dying bark of trees and stumps of spruce throughout the 

 Northern States. The adult beetles are stout, cylindrical, black, 

 and about y 8 inch long. They construct a central nuptial chamber 

 in the inner bark, from which radiate three to five short, curved 

 egg galleries. There appears to be only one annual generation. 

 They breed in all western spruces and also have been recorded 

 from lodgepole pine, limber pine, larch, and Douglas-fir. 



HEMLOCK BARK BEETLES 



While hemlocks have a number of bark-beetle enemies, these 

 are mostly of secondary importance, and seldom are any large 

 number of trees killed. 



Western hemlock is sometimes attacked and killed by the 

 Douglas-fir beetle (p. 155) when associated with Douglas-fir. At 

 times weakened trees are attacked by species of Scohjtus and 

 Pseudohylesinus. 



Mountain hemlock, when in mixture with lodgepole pine, is 

 sometimes killed by the mountain pine beetle (p. 135), but is most 

 frequently attacked by a species of Scohjtus. 



The hemlock engraver (Scohjtus tsugae (Sw.)) is a small, dark, 

 shiny bark beetle about y 8 inch long, with the wing covers pro- 

 jecting over the concave abdomen. It constructs a short, straight 

 egg tunnel across the grain, from one or both sides of a small 

 entrance chamber. Mountain hemlock, western hemlock, and Doug- 

 las-fir are attacked. At times the species is very destructive. It is 

 distributed from British Columbia southward into California and 

 eastward into Idaho. 



The hemlock hylesinus {Pseudohylesinus tsugae Sw.) is a stout, 

 oval bark beetle about y s inch long, reddish brown, and sparsely 

 clothed with scales and short, stout hairs. It breeds prolifically 

 in felled and dying western hemlock and also is known to attack 

 Pacific silver fir. It sometimes kills apparently healthy trees. It is 

 reported from British Columbia, Washington, Oregon, and Cali- 

 fornia. 



