Phenology and Distribution of Aquatic Dance Flies (Diptera: Empididae) in a Laurentian Watershed

Adult dance flies were collected from emergence traps (73 trap-years) and with a beating net in 1972-1974 and in 1978 in eight mainstream stations, 13 tributaries and six lakes of a Laurentian watershed. Some 2670 specimens were identified belonging to 18 species, eight of which are apparently new records for Quebec. Except for the early-emerging Clinc the other species appear to be univoltine. There is a rapid succession in the appearance of species in June; the males are relatively short-lived, whereas the females often persist throughout the summer. Hemerodromia captus is lentie, occurring in two of the lakes; H. melanosoma, though predominantly lotie, also inhabits one of the lakes, and all the other species are restricted to lotie habitats. The species of Chelipoda, Chelifera and Thanay tegia are more or less confined to small headwater streams, while those of Hemerodromia, Neoplasia and Roederiodes typically inhabit the mainstream and the larger tributaries. Most of the mainstream species seem to prefer fast waters on a substrate of moss and rubble, though individual species differ in their stenotopy.