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 monticolae 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 prothorax 
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. SI. 
