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Abstract:
About one million Ephemeroptera emerge from the Breitenbach, Hesse, FRG, every year. Some 30,000 specimens taken in 1983 and 1984 in a series of emergence traps along a 2,000 m section of the stream are analysed. The total number of species in the stream is 16. However, only six species occur every year and even less contribute significantly to numbers emerging. Temporal patterns, diversity and distribution along the stream are examined in detail. All agree well between years, thereby reflecting the homogeneity of the system. A modified, density-corrected Shannon-Weaver index of diversity is proposed.
