154 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



teeth, the second and third pairs of teeth being larger on the 

 males. Their work is similar to that of Pity o genes, and they are 

 frequently found under the thick bark of ponderosa, Jeffrey, and 

 lodgepole pines in small mines, intermingling their work with that 

 of the pine beetles. Another species, 0. vicinns (Lee.) closely re- 

 lated to the eastern 0. caelatus (Eichh.), infests lodgepole and 

 western white pines, Engelmann spruce, and western larch in 

 Colorado and the Northwestern States and Canada. 



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. 37) . 



Other Secondary Bark Beetles 



A number of secondary bark beetles belonging to the genera 

 Hylastes, Hyhirgops, and Pseudohylesinus are commonly found 

 in the inner bark of dying pine, spruce, fir, and hemlock, and 

 are frequently mistaken for destructive species. Actually, they 

 seldom or never cause the death of healthy trees by their unaided 

 efforts. 



Species of the genus Hyhirgops are often referred to as sour- 

 sap beetles, since they are most commonly found in the wet fer- 

 menting inner bark at the base of trunks or in the main roots of 

 dying or dead trees, or in freshly cut stumps. H. subcostulatus 

 (Mann.) a small russet-brown, scaly beetle about % 6 inch long, 

 excavates a short, slightly curved, longitudinal egg gallery in the 

 moist inner bark of ponderosa, sugar, Jeffrey, shore, lodgepole, 

 and western white pines throughout the West. H. rugipennis 

 (Mann.) is a narrow reddish beetle, slightly longer than the above, 

 which works in pines, Engelmann spruce, and western hemlock 

 in the Pacific coast and northern Rocky Mountain regions. H. 

 porosus (Lee.) is less common than the two above-named species, 

 but has been recorded from nearly all pines throughout the West. 

 H. lecontei Sw. is also widely distributed and has been recorded 

 from lodgepole, Monterey, and ponderosa pines, and white fir in 

 western United States. 



Species of Hylastes are small, elongate, dull-brown to black 

 beetles, which are also found under the bark and in roots of dying 

 or dead conifers and breeding in slash. Often the adults fly in 

 great numbers and are picked up around sawmills and lumber 

 piles. Reported "swarms of pine beetles" often are one or more 

 of these species, for the more destructive pine beetles are not often 

 taken in flight. Occasionally where large swarms of these beetles 

 emerge they will feed on the tender bark of young trees, and 

 small trees an inch or more in diameter may be killed by beetles 

 girdling the bark at or below the root collar. These beetles may 

 also be found breeding in the roots of suppressed or weakened 

 seedlings. 



Several western species have been found doing this type of dam- 

 age. Hylastes gracilis Lee, a dark reddish-brown beetle % 6 inch 

 long, is commonly taken in flight. It is reported breeding in pon- 

 derosa, sugar, and pinyon pines and white fir throughout the West. 



