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



distinctive in that no well-defined 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. P. serrahis Brack is a related species 

 which attacks bigcone spruce in southern California. 



The grand fir bark beetle (Pseudohylesinus grandis Sw.) attacks 

 the trunks or limbs of weakened or dying Douglas-fir, and grand, 

 white, Pacific silver, alpine, and red firs. It usually is of secondary 

 importance. The adult beetles are about y 8 inch long, rather stout, 

 elongate-oval, densely covered with brown and gray scales which 

 sometimes form V-shaped markings on the wing covers. They work 

 in pairs and each pair constructs a short, transverse egg gallery 

 for 2 or 3 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 is narrower, 

 not so uniformly straight, and without the well-defined entrance 

 chamber. There are one or two generations a year, depending on 

 the locality. It is distributed from California to Alaska and east- 

 ward into Montana. 



The noble fir bark beetle (Pseudohylesinus nobilis Sw.) is very 

 similar to the above and is found breeding in dying noble fir and 

 Pacific silver fir in Oregon and Washington. 



The fir root bark beetle (Pseudohylesinus granulatus (Lee.)) is 

 a larger, very dark reddish to black species about y 5 inch long, 

 with very rough elytra and prominent striae. It is a secondary 



Figure 76. — Galleries of the western balsam bark beetle 

 (Dryocoetes confusus) . 



