106 



THE SCOLYTID BEETLES. 



This species is easily separated from its nearest relative, the Doug- 

 las fir beetle, by its smaller size and eastern distribution, and from 

 eastern forms by its medium size, convex and deeply grooved declivity, 

 the character of its gallery, and its occurrence in larch. 



Fig. 64.— The eastern larch beetle: Distribution map. (Author's illustration.) 



BIBLIOGRAPHY. 



Schwarz, 1888, p. 175; Packard, 1890 (under Dendroctonus sp.?), p. 903; Harring- 

 ton, 1891, p. 27; Hopkins, 1898&, pp. 104-105; Hopkins, 1899a, pp. 394, 447; Hopkins, 

 1909, pp. 117-121. 



No. 13. THE DOUGLAS FIR BEETLE. 



{Dendroctonus pseudotsugae Hopk. Figs. 65-69.) 



The Douglas fir beetle is a stout, reddish to blackish-brown, cylin- 

 drical barkbeetle, 4 to 7 mm. in length, its head broad, convex, with 

 shallow longitudinal- groove behind the middle ; the pro thorax short, 

 broad, punctured, with sides somewhat rounded and strongly nar- 

 rowed and constricted toward the head; the elytra with rather 

 coarse rugosities between the rows of punctures ; the declivity convex, 

 with striae deeply grooved and intervening spaces convex and nearly 

 smooth or roughened, and the body with numerous long hairs. (See 

 tig. 65.) It attacks injured, dying, felled, and living Douglas fir, 

 bigcone spruce, and western larch, wherever these trees grow from 

 British Columbia southward into New Mexico, Arizona, and Cali- 

 fornia. It excavates long, straight, or slightly winding egg galleries 

 through the inner bark, and grooves the surface of the wood, the 

 eggs being placed in alternate groups along the sides; the long larval 



