INSECT ENEMIES OF WESTERN FORESTS 125 
nuptial chamber is visible on the inner surface of the bark. The 
larval mines diverge from the egg gallery and end in pupal cells 
in the inner bark. There appear to be two generations a year. 
The grand fir bark beetle (Pseudoh ylesinus grandis Sw.) attacks 
the trunks or limbs of w eakened 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 w hich 
sometimes form V- shaped markings on the wing covers. ea work 
in pairs and each pair constructs a short, transverse ege gallery 
for 2 or 8 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 1s narrower, 
not so uniformly straight, and without the well defined entrance 
chamber. There are one or two generations a year, depending on 
the locality. 
The fir root bark beetle (Pseudohylesinus granulatus Lec.) 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 
1s a secondary enemy of grand fir and white 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 Califorma to British 
Columbia. 
The noble fir bark beetle (Pseudohylesinus nobilis Sw.) 1s 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 working under the 
bark of firs. While 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 several radiating egg 
galleries which may score the sapwood (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 BARK BEETLES 
Spruce trees are attacked by a large number of bark beetles, 
most of which are secondary enemies, bre eeding only in dying, felled, 
or weakened trees. A few species, however, such as the Englemann 
