INSECT ENEMIES OF WESTERN FORESTS 165 



lery. Beetles fly and make new attacks mostly during May and 

 June, and new broods complete their development to new adults 

 before winter. There is one generation a year, which passes the 

 winter mostly in the adult stage, and a partial second generation, 

 which overwinters as larvae. No control work has been attempted 

 for this bark beetle. 



Many species of small engraver beetles, which breed in the dying 

 bark of felled or weakened trees, sometimes become so plentiful 

 as to bcome dangerous to small spruce trees and the tops of older 

 trees. These belong to the same genera that are met with in pines 

 and firs. 



The Sitka spruce engraver (Ips concinnus Mann.) attacks the 

 bark of living, dying, or felled Sitka spruce along the coast of 

 Oregon and northward to Alaska. No reports have been received 

 of its having done more than nominal damage. The adults are 

 about % inch long, with three teeth, one very prominent and two 

 smaller, on each side of the concave elytral declivity. They ex- 

 cavate an irregular central nuptial chamber, with three or four 

 short curved or S-shaped galleries radiating therefrom. Four eggs 

 are laid in each egg pocket and the four larval mines issuing from 

 each pocket are a characteristic feature of its work. (See p. 144 

 for a general discussion of the work and habits of the Ips beetles.) 



Other species of Ips which attack spruce include the following : 



Species of Ips Host and distribution 



perturbatus (Eichh.) White spruce. Northern Canada and Alaska. 



interpunctus (Eichh.) White spruce and Engelmann spruce. Alaska, 



Yukon, and British Columbia. 

 interruptus (Mann.) Sitka spruce, white spruce. Oregon to Alaska 



and eastward. 

 dubius Sw Engelmann spruce. British Columbia and 



Canadian Rockies. 

 tridens (Mann.) Engelmann, Sitka, and probably white spruces. 



Canadian Rockies, British Columbia, and 



Washington. 



engelmanni Sw Engelmann and white spruces in same region. 



pilifrons Sw Engelmann spruce. Idaho and Colorado. 



The Sitka spruce hylesinus (Pseudohylesinus sitchensis Sw.) is 

 a small, densely scaly, suboval bark beetle which is found attack- 

 ing limbs and twigs of felled or dying Sitka spruce in British 

 Columbia, Washington, Oregon, and California. It makes a short, 

 1-inch, slightly curved, longitudinal egg gallery with a shoe-shaped 

 entrance. The larvae work laterally and pupation occurs in the 

 bark or slightly submerged in the sapwood. 



Dryocoetes affaber Mann, attacks the tops of felled and dying 

 Sitka, Engelmann, and other spruces, and Douglas-fir from Alaska 

 southward into the Northwestern States. The adults, which are 

 less than y 8 inch in length, construct irregular, short egg galleries. 



Dryocoetes confusus Sw. (p. 163) may also be found attacking 

 and sometimes killing Engelmann and other spruces. 



Scolytus piceae (Sw.) attacks white spruce in eastern Canada, 

 but extends westward into Alberta, South Dakota, North Dakota, 

 Montana, Wyoming, and Colorado, where it may be found on En- 



