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Zusammenfassung:
The 1976 emergence rate of Empididae and Dolichopodidae (Insecta, Diptera, Brachycera) from a woodland stream near Bonn was investigated by the greenhouse method developed by Illies (1971). The list of species (Empididae: 82 spp.; Dolichopodidae: 24 spp.) is presented with additional remarks on larval ecology, adult phenology and the biogeographical distribution patterns of all the species involved. With 0.701 g 1.7 m² . yr., aquatic Empididae (10 spp.; 1265 individuals) amounted to 3.4% of the total insects that emerged in 1976. Aquatic Dolichopodidae (13 spp.; 2611 individuals) contributed 1786 g 1.7 m² . yr. and 8.6% to the total catch of merolimnic insects. As the present knowledge on larval behavior and substrate preferences of both groups is still poor, the above-mentioned figures may even be higher. Species composition, abundances and emergence biomass of both groups are discussed comparatively for Annaberger Bach (Bonn) and Breitenbach (Schlitz) (Wagner 1980) to demonstrate the basic differences between an astatic woodland stream with a high import of allochthonous material and a meadow stream with autochthonous plant communities.
