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要旨:
Abstract
It takes Isoperla goertzi and Diura bicaudata two and Perlodes microcephala one year to complete a generation. Differences in the lengths of the life cycles are to be explained by characeristics of the three stages: egg, nymph, and adult.
In an artificial stream D. bicaudata is found to migrate upstream more actively and to drift less frequently than I. goertzi. Drift and upstream movement of nymphs of D. bicaudata in the Lauter creek maintain a steady population. In contrast there is a steady loss during the nymphal life of I. goertzi, and the balance is restored during the adult stage.
