. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. 86 THE SCOLYTID BEETLES. wood to blue long before the leaves begin to fade. Except for the secondary injuries by wood-boring insects, fire, etc., the heartwood of the larger trees will remain sound and valuable for several years. While, however, there may not be a very great loss from leaving the dead timber standing until the heartwood begins to deteriorate, the danger of destruction by forest fires is so great that, in order to insure. Fig. 48.—Two giant sugar-pine trees killed by the mountain pine beetle, and
. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. 86 THE SCOLYTID BEETLES. wood to blue long before the leaves begin to fade. Except for the secondary injuries by wood-boring insects, fire, etc., the heartwood of the larger trees will remain sound and valuable for several years. While, however, there may not be a very great loss from leaving the dead timber standing until the heartwood begins to deteriorate, the danger of destruction by forest fires is so great that, in order to insure. Fig. 48.—Two giant sugar-pine trees killed by the mountain pine beetle, and one dying from recent attack, Yosemite National Park, Cal. Note horse and man by dying tree, indicating diameter of tree at base. Approximate diameter, 8 feet. (Original.) against complete loss, the attacked and infested timber should be felled and utilized before the broods of the beetle develop and emerge, or within two or three years. FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. Favorable conditions for the multiplication and destructive work of this insect are found in so-called primitive forests with a predomi- nance of mature timber, and where trees are frequently struck by. 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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