. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. THE GENUS DENDROCTONUS. 95 ECONOMIC FEATURES. This species apparently differs from all of the others in its decided preference for living timber, in which it excavates its egg galleries in such a manner as to kill the tree and make the conditions favorable for the development of its broods. It is, therefore, a primary enemy of the first importance, especially as related to the western yel- low pine in the eastern sec- tion of the Rocky Moun- tain region south of east- ern Montana. It has de- stroyed a vast amount
. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. THE GENUS DENDROCTONUS. 95 ECONOMIC FEATURES. This species apparently differs from all of the others in its decided preference for living timber, in which it excavates its egg galleries in such a manner as to kill the tree and make the conditions favorable for the development of its broods. It is, therefore, a primary enemy of the first importance, especially as related to the western yel- low pine in the eastern sec- tion of the Rocky Moun- tain region south of east- ern Montana. It has de- stroyed a vast amount of the best timber in the Black Hills National Forest of South Dakota, and is threatening the destruction of practically all of the best timber there, as well as much of the reproduction. It is also destructive to the pine in Colorado, New Mexico, and Arizona. There is evi- dence that extensive forests have been destroyed in Col- orado by this beetle and by resulting forest fires during the past fifty or seventy- five years. EVIDENCES OF ATTACK. The first evidence of at- tack and infestation on liv- ing timber is the appear- ance of pitch tubes on the bark of the main trunk, or, in the absence of these, of reddish borings lodged in the loose bark and on the ground around the base of the trees. This is usually the only ex^ ternal evidence from the time the trees are attacked in the summer and fall until the following spring. Sometimes during the winter, and especially in the period from April to June, the more noticeable evi-. Fig. 55.—The Black Hills beetle: a, Pitch tubes on sur- face of bark, reduced; b, same, two-thirds natural size. (Author's illustration.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Bureau of Entomology. Washington : G. P. O.
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