80 



THE SCOLYTID BEETLES. 



sented in the forest-insect collection of the Bureau of Entomology by 

 more than 150 specimens. 



This species is closely allied to No. 7, of Mexico, and was at one time 

 thought by the writer to be a variety of it, a but recent studies indi- 

 cate that it is a good species, distinguished by the more shining pro- 

 notum, more distinctly narrowed and faintly constricted toward the 

 head, the hairs on the sides toward the base slender and less numer- 

 ous. Therefore it is thought best to retain it as a good species. It 

 is easily distinguished from the other species associated with it in the 

 same region by its elongate form, larger size, and by the deep frontal 

 groove of the head and stiff, erect, blackish hairs on the declivity. 



Fig. 43.— The Colorado pine beetle: Distribution map. (Author's illustration.) 



BIBLIOGRAPHY. 



Schwarz, 1902, p. 32; Hopkins, 1903a, p. 61; Hopkins, 1904, p. 44; Hopkins, 1905, 

 p. 11; Hopkins, 1906c, p. 81; Hopkins, 1909, pp. 101-104. 



No. 9. THE MOUNTAIN PINE BEETLE. 



(Dendroctonus monticolx Hopk. Figs. 44-50.) 



The mountain pine beetle is a stout, black, cylindrical barkbeetle 

 3.7 to 6.4 mm. long, having the head broad, without frontal groove, but 

 with a short longitudinal impression above the middle; the pro thorax 

 short, broad, and punctured, with sides narrowed and slightly con- 

 stricted toward the head; the elytra with moderately coarse rugosi- 

 ties between rows of punctures, the latter usually indistinct on the 

 sides; the declivity slightly impressed each side of the suture, and 



aProc. Ent. Soc. Wash., VII, p. 81. 



