INSECT ENEMIES OF WESTERN FORESTS 169 



cristatus Lee, are at times very destructive to Monterey and other 

 cypresses in California. Besides killing many trees outright, they 

 mine and kill the twigs of ornamentals, making them very un- 

 sightly. Other small species of cedar bark beetles which work 

 mainly in twigs are discussed on page 39. 



BARK BEETLES AFFECTING BROADLEAVED TREES 



Certain species and genera of bark beetles confine their attacks 

 to various broadleaved forest trees. Some of these are important 

 enemies of shade trees, park trees, and ornamentals. Some of the 

 more common are mentioned in the following paragraphs. 



The alder bark beetle (Alniphagus aspericollis Lee.) is a com- 

 mon and often destructive enemy of western alders from British 

 Columbia southward through California. The beetles usually at- 

 tack weakened, dying, or felled trees. The adults are small, robust 

 bark beetles about % inch long. They bore through the bark in 

 pairs, usually at the base of branches, and construct a longitudinal 

 egg gallery from 2 to 5 inches long, with no apparent nuptial cell. 

 Eggs are placed close together along both walls of the gallery, 

 with as many as 50 eggs to the inch. The larvae work out from 

 the egg gallery and pupate in the soft inner bark. There appear 

 to be two generations a year, and attacks occur throughout the 

 growing season. 



The ash bark beetle (Leperisinus aculeatus (Say)) breeds in 

 felled, injured, or dying ash trees and under certain conditions 

 may be injurious to living trees. It follows the distribution of its 

 host trees from the Atlantic to the Pacific and has been recorded 

 from Oregon, California, and New Mexico. 2 The adults are small, 

 dark-brown bark beetles % inch in length, marked with grayish 

 and dark scales. They construct uniform egg galleries beneath the 

 bark with two transverse branches starting from a central en- 

 trance chamber. In the smaller limbs the galleries extend obliquely 

 around the limbs and may completely encircle them. Ash bark 

 beetles are frequently very abundant in ash cordwood. 



The oak bark beetles (Pseudopityophthorus spp.) sometimes at- 

 tack so heavily as to cause the death of weakened oak trees. 

 Usually, however, these beetles confine themselves to injured, 

 felled, or recently killed trees or to the dead branches and twigs 

 of otherwise healthy trees. The adults are tiny, cylindrical, brown 

 bark beetles. Their typical work consists of transverse egg gal- 

 leries extending for a short distance on either side of the central 

 entrance tunnel and diverging larval mines running longitudinally 

 with the trunk or limb. 



The birch bark beetle (Dryocoetes betulae Hopk.) is a secondary 

 enemy of birch throughout British Columbia, Canada, and the 

 northern part of the United States. 



FLATHEADED BORERS 



The flatheaded or metallic wood borers (Buprestidae) (21) 

 comprise a large family of beetles, the larvae of which mine in 



2 The western form of this species may represent a closely related unde- 

 scribed species. 



