Biology and Downstream Drift of Some Oregon Trichoptera

Data are given on the biology of several species of Trichoptera in the Metolius River, Oregon, based on drift and benthos samples. Twenty-seven species were collected. Species of Limnephilidae, Brachycentridae, Hydroptilidae, and Lepidostomatidae were important drift components. The Metolius River is extremely productive, with a mean density of larval Trichoptera of 7400 per square meter in benthos samples and a maximum of 5000 per 24 hours in drift-trap samples. Different species varied in their tendency to drift, in the age class distribution in the drift, and in diel periodicity. Drift-trap collecting is shown to be a useful method of studying aspects of behavior such as the dispersal of larvae and the emergence of pupae.