Life cycles and drift of Trichoptera from a woodland stream in Minnesota

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Abstract
Life cycles of Trichoptera from a stream riffle were determined from analyses of monthly size–frequency distributions of larvae, pupal densities, and observations of adult emergence. Two types of univoltine life cycles were observed (H. B. N. Hynes' classification): slow seasonal for Brachycentrus americanus, Brachycentrus occidentalism and Micrasema kluane, and fast seasonal for Lepidostoma bryanti. The life cycle for Glossosoma intermedium was primarily bivoltine with summer and winter generations; however, some larvae of the summer generation were suspected to overwinter as pupae or terminal instar larvae and emerge in the spring. Larval B. americanus and L. bryanti showed peak drift prior to pupation and emergence which thus appeared seasonally associated with life cycle. Stream drift of M. kluane and G. intermedium was low and exhibited no clear association with life cycle or season. Drift of B. americanus, M. kluane, L. bryanti, and G. intermedium was not correlated to standing stocks (p < 0.05).
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