THE BLACK HILLS BEETLE. 



11 



The following description of distinctive characters of the beetle, 

 its work, habits, life history, etc., is based on the results of our 

 studies of the species in the field and laboratory, brought up to date, 

 regardless of what has been previously published or given out in 

 correspondence. 



CHARACTERS OF THE BEETLE (FIG. 1). 



The distinctive characters of the Black Hills beetle are its length, 

 which is from one-sixth to one-fourth of an inch; its stout form, 

 with broad head and pro thorax; its black color, and the rounded 

 or convex rear end of the body (declivity of the elytra), which is 

 without conspicuous long hairs. The allied species, which may be 

 mistaken for it, are distinguished as follows: The large red turpen- 

 tine beetle (Dendroctonus valens Lee.) is much larger, is dark reddish 

 in color, never black, and forms large 

 masses of pitch at or toward the base of 

 living and dying pine trees and stumps. 

 The Colorado Dendroctonus (D. approxi- 

 mate Dietz) is black, with broad head, 

 but the body is more elongate, the front 

 of the head is grooved, and the declivity 

 of the elytra has long, stiff hairs; it fives 

 in the bark of pine, but makes a winding, 

 sometimes branched, gallery. The spruce- 

 destroying beetle (Dendroctonus piceaperda 

 Hopk.) is reddish brown to black, but with 

 much narrower head, with long hairs on the 

 declivity of the elytra, and is always found 

 in spruce. The Douglas spruce beetle 

 (Dendroctonus pseudotsugse n. sp.) is dark red or brown, and always 

 breeds in Douglas spruce and western larch. The species which most 

 closely resembles the Black Hills beetle is the mountain-pine beetle 

 (Dendroctonus monticola Hopk.), which is only distinguished in the 

 adult stage by the smaller size, slightly less stout form, less dis- 

 tinctly roughened elytra, and more obscured rows of punctures on 

 the sides of the elytra, the latter being the most important char- 

 acter for its distinction. 



CHARACTERS OF THE GALLERY (FIGS. 2 AND 3 AND PL. i). 



The primary gallery excavated in the bark by the Black Hills 

 beetle is distinguished from that of any other species as yet known 

 to live in the pine of the Black Hills or Colorado by the slight curve 

 at the entrance end and the almost straight course with the grain 

 through the inner layers of bark, and grooving the surface of the 

 wood. There is only one pine-infesting species with which this form 



Fig. 1 — The Black Hills beetle: a, 

 adult, enlarged: b, same, natural 

 size. (Author's illustration.) 



