Preliminary observations on the distribution and abundance of seaweed flies (Diptera: Coelopidae) on beaches in the Gosford district of New South Wales,Australia

Abstract Thirteen species of the family Coelopidae occur in beach wrack on Australian coasts, predominantly at temperate latitudes. Four species (This canus, Chaetocoelopa sydneyensis (Schin.), Amma blancheae and Dasycoelopa australis Mall.) can be caught on beaches in the Gosford district, New South Wales. Seasonal changes in the distribution of coelopid species may be linked with seasonal weather variations. Field and laboratory data on the commonest and most abundant species, T. canus, suggest that variations in adult abundance could be due to fluctuations in high tide level governing the rate of the coelopid life cycle. Local weather conditions and human influences may modify the effects of the high tides.