Life histories of some filter-feeding Trichoptera in Virginia

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Abstract
Life histories were determined for seven species of filter-feeding Trichoptera at two sites on the impounded North Anna River and at two sites on the free-flowing South Anna River in the Piedmont of Virginia, U.S.A. Hydropsyche incommoda, H. sparna, and H. venularis were trivoltine at at least three of the four sites, with fast-growing spring and summer generations that matured in June and July, and August and September, respectively, and a slow-growing winter generation that matured in March, April, and May. Cheumatopsyche parentum, Macronema zebratum, Chimarra moselyi, and C. obscura were bivoltine at all sites. The summer generations of these species grew quickly, maturing in June and July, and the winter generation grew slowly, maturing in April and May. Instars I–V, pupae, and adults of most species were present continually from April through October. All species overwintered in instars III–V, and in most species instar II was present during the winter also. Comparisons of Hydropsyche life histories in the Anna Rivers with those reported from other eastern North America rivers reveal that differences in voltinism are probably due to a complex interaction of food quality and temperature regime.