AS MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 
weakened, dying, and newly felled trees; but, like other secondary 
species, under favorable conditions they may develop in sufficiently 
large numbers to attack and kill small trees growing in the vicin- 
ity of their breeding place. The adults are small, dark-brown 
beetles, with small, spinelike teeth along the margin of a slightly 
concave elytral declivity. They are polygamous and excavate nu- 
merous galleries under the bark, which radiate from a central, more 
or less circular, nuptial chamber. 
Pityogenes carinulatus Lec. breeds in ponderosa, lodgepele, white- 
bark, Jeffrey, and probably other pines and is distributed over 
nearly all of the Western States. The adults are slender, reddish- 
brown bark beetles about one-eighth inch in length. The females 
have three small, spinelike teeth along each margin of the elytral 
declivity, whereas the males have only two declivital teeth on each 
side, the first pair strongly developed into prominently curved spines. 
Their gallery pattern consists of from 8 to 10 or more rather slender 
egg galleries from 1 to 2 inches in length, radiating from a circular 
entrance chamber. 
Pityogenes knechteli Sw. is a stout species about one-eighth inch 
long, commonly found associated with 7ps and Dendroctonus beetles 
under the thin bark of lodgepole pines in the Western States and in 
British Columbia, and is sometimes responsible for the destruction 
of small patches of lodgepole pine in reproductions. The work 
consists of from three to five egg galleries 114 to 3 inches in length, 
radiating from the central nuptial chamber. 
Pityogenes fossifrons Lec. is a species occasionally found working 
in the tops and limbs of weakened or dying western white pine and 
lodgepole pine from California northward to British Columbia 
and eastward to Idaho. Its attacks are seldom primary, though it 
sometimes attacks western white pine reproduction. The adults are 
small, brownish-black bark beetles approximately one-eighth inch 
in length with three very small spines along each margin of the 
elytral declivity. Their gallery pattern consists of four or five egg 
tunnels 1 to 114 inches in length, radiating from the entrance or 
nuptial chamber (fig. 58). 
Several other species of small engraver beetles may be encountered 
under the bark of pines. Ovthotomicus ornatus Sw. is a very small 
species about one-eighth inch in length. The elytral declivity is 
shghtly concave, with three pairs of small teeth, the second and third 
pairs of teeth larger on the males. Their work is similar to that 
of Pityogenes, and they frequently are found under the thick bark 
of ponderosa, Jeffrey, and lodgepole pines in small mines inter- 
mingling their work with that of the pine beetles. Some species of 
the genus Pityophthorus are occasionally found under the thick 
bark of dying pines, and may be responsible for the death of 
weakened trees (p. 31). 
Fir Bark BEETLES 
The balsam firs (Abzes spp.) and Douglas fir (Pseudotsuga taai- 
Folia), as well as pines, have their full share of bark-beetle enemies 
(19). In general the destructive species are different from those 
attacking pines, though many of the secondary species may be the 
same. Douglas fir growing under favorable conditions in the com- 
