124 ^nSC. PUBLICATIOX 278, U. S. DEPT. OF AGRICULTURE 



galleries in tlie limbs of balsam firs; S. praeceps Lee. a small species 

 about one-eighth inch in length, which attacks the limbs and small 

 tops of white fir and other firs in the Western States; and .S'. mo?iti- 

 colae Sw., about one-eighth inch in length, which is recorded by 

 Swaine as attacking western white pine and Douglas fir in British 

 Columbia. 



Some of the species of the genus Pseudohylesinus are also quite 

 frequently found in various hrs. They usually are secondary in 



habit but a t t i m e s 

 some species are de- 

 structiye. Their work 

 is yery similar to that 

 of ScoJytus in that the 

 typical Q gg gallery 

 consists of two short, 

 straight branches from 

 a central entrance tun- 

 nel. The work usu- 

 a 1 1 y can be distin- 

 guished from ScoJytus 

 in that no enlarged 

 nuptial chamber, scor- 

 ing t h e sapwood or 

 fusible on the i n n e r 

 surface of the bark, is 

 constructed, as is the 

 case with Scolytus. 

 Another distinguish- 

 ing feature between 

 these two genera is 

 that the wing covers 

 of Pse udo h yiesinus are 

 densely covered with 

 scales, a n d therefore 

 are dull in appearance 

 i n s t e a d of shiny. 

 Moreover, the beetles 

 are nearly oval in out- 

 line and do not have 

 the concavity at the rear of the abdomen which is such a distinctive 

 feature of ScoJytus. 



The Douglas fir hylesinus {PseudohyJesinus neljuJosus Lee.) is fre- 

 quently found attacking recently felled or injured small Douglas 

 firs through the range of this tree from British Columbia to central 

 California. It seems to prefer the thin bark of saplings, or poles, 

 or limbs of larger trees, and frequently kills trees of small diameter. 

 The adults are small, gra^ush to yellowish-brown, variegated bark 

 beetles about one-eighth inch in length. Usually a short longi- 

 tudinal Qgg gallery is constructed in the cambium layer, often with 

 two branches, originating from a central entrance tunnel, one up 

 and one down the trunk, parallel with the grain of the wood (fig. 

 62). Their work is very similar to and easily confused with that 

 of ScoJytus unispinosus^ but is distinctive in that no well-defined 



FiGUEE 62. — Adults and galleries of the Douglas fir hylesi 

 iius {Pseudohylesinus nehulosus) , natural size. 



