Title: Eastern forest insects
Identifier: easternforestins1175bake (find matches)
Year: 1972 (1970s)
Authors: Baker, Whiteford L. (Whiteford Lee), 1903-
Subjects: Forest insects
Publisher: Washington : U. S. Dept. of Agriculture, Forest Service ; for sale by the Supt. of Docs. , U. S. G. P. O
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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F-519939-40 Figure 93.—The native elm bark beetle, Hylurgopinus rufipes: top, adult; bottom, gallery pattern.
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Winter is spent in the bark of elm trees in either the larval or adult stages. Overwintering adults emerge during May and fly to living trees and feed in the bark. Later they fly to dead and dying trees, broken limbs, or recently cut logs or limbs to breed. Usually, dying or fairly moist dead limbs at least 2 inches in diameter are selected. Entrance holes are made in bark crevices or under overhanging bark flakes and they penetrate directly to the surface of the wood. A biramous egg gallery is constructed with the arms extending away from the entrance hole at various angles (fig. 93). The gallery may be constructed horizontally, but is most often inclined from the horizontal. Galleries may be constructed entirely in the bark, or they may scar the wood slightly. Eggs are laid on both sides of the gallery, sometimes very close together. Young larvae feed away from the gallery, usually following the grain. Pupation occurs in cells at the end of the larval tunnels in the bark. There appears to be two gen- erations per year in the southern portions of the insect's range. In the northern portions there may be only one or one and a partial second (410). When the adults emerge from elms dying from Dutch elm dis- ease, they often carry spores of the disease-causing fungus on their bodies. When they bore into the bark of healthy elms to feed or hibernate, some of the spores rub off onto the walls of their tunnels, inoculating the tree with the disease. In most parts of the United States, the spread of the disease by the native elm bark beetle is secondary to its spread by the much more abundant smaller European elm bark beetle. Farther north in Canada, 251

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