INSECT ENEMIES OF WESTERN FORESTS 125 



nuptial chamber is visible on the inner surface of the bark. The 

 larval mines diverge from the eoor gallery and end in pupal cells 

 m the inner bark. There appear to be two generations a year. 



The grand fir bark beetle {Pseuclohylesinus grandis Sw.) attacks 

 the trunks or limbs of weakened or dying Douglas fir, lowland 

 white fir, and white fir, and is usually of secondary importance. 

 The adult beetles are about one-eighth inch in length, rather stout, 

 elongate-oval, densely covered with brown and gray scales which 

 sometimes form V-shaped markings on the wing covers. They w^ork 

 in pairs and each pair constructs a short, transverse o^gg gallery 

 for 2 or 3 inches, sometimes on only one side but more frequently 

 on both sides of the entrance tunnel. The work is very similar to 

 that of Scolytus ventralis except that the egg gallery is narrower, 

 not so uniformly straight, and wdthout the w^ell defined entrance 

 chamber. There are one or two generations a year, depending on 

 the locality. 



The fir root bark beetle {Pseudohylesinus granulatiis Lee.) is a 

 larger, very dark reddish to black species about one-fifth of an 

 inch in length, with very rough elytra and prominent striae. It 

 is a secondary enemy of grand fir and Avhite fir, working under the 

 bark of dying or dead trees, particularly at the base and in the 

 roots of small trees. It is distributed from California to British 

 Columbia. 



The noble fir bark beetle {Pseuclohylesinus nohilis Sw.) is similar 

 to P. grandis, approximately one-eighth inch in length, and is found 

 breeding in dying noble fir. 



Some of the species of Dryocoetes are found w^orking under the 

 bark of firs. Wliile they are usually secondary enemies, they at 

 times attack and kill apparently healthy trees. 



The western balsam bark beetle Dryocoetes confusus Sw. is prob- 

 ably the most destructive member of the group and is quite often 

 found attacking alpine fir and sometimes other species of fir and 

 spruce. The adults are rather short, reddish-brown bark beetles 

 about one-eighth inch in length. They construct a small, circular 

 nuptial chamber under or in the bark, with scA^eral radiating Qgg 

 galleries which may score the sap wood (fig. 63). There is probably 

 only one generation a year. The species is distributed throughout 

 the Northwestern States from British Columbia southward in Oregon 

 and eastward to Colorado. 



Dryocoetes pseudotsugae Sw. is a secondary enemy of Douglas 

 fir. The adults are reddish brown and are about three-sixteenths 

 of an inch in length. They construct short, irregular galleries in 

 the inner bark of wind-thrown and dying trees throughout Cali- 

 fornia and northward to British Columbia. The young adults gather 

 in galleries in the outer or inner bark, not in the cambium, to pass 

 the winter. Emergence occurs early in the spring. Trees attacked 

 in the spring produce mature beetles by August. There probably 

 are one and a partial second generation each year. 



Spruce Baek Beetles 



Spruce trees are attacked by a large number of bark beetles, 

 most of which are secondary enemies, breeding only in dying, felled, 

 or weakened trees. A f ew^ species, however, such as the Englemann 



