1]^3 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 Lee. breeds in ponderosa, lodgepcle, 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 

 ^gg 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 Ips 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 II/2 to 3 inches in length, 

 radiating from the central nuptial chamber. 



Pityogenes fossifrons Lee. is a species occasionally found working 

 in the tops and limbs of weakened or dying w^estern 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 ^^^ 

 tunnels 1 to 1% 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. Orthotomicus ornatus Sw. is a very small 

 species about one-eighth inch in length. The elytral declivity is 

 slightly 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 w4th 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 {Abies spp.) and Douglas fir {Pseudotsuga taxi- 

 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- 



