Strongylophthalmyia pengellyi n . sp ., a second species of nearctic Strongylophthalmyiidae abstract

Strongylophthalmyia pengellyi new species is described from Canada (New Brunswick, Ontario, Québec) and the United States (Michigan, Utah). A key is provided to distinguish it from the only other Nearctic species, S. angustipennis Melander. The species shows unusual sexual dimorphism of the legs and of the wing. Copulatory posture suggests function for some of these modifications. Adult S. pengellyi were sampled with sticky traps, Malaise traps, and by searching tree trunks. An association with decrepit trembling aspen is presumed based on occurrence of adults of both species on tree trunks and the larvae of S. angustipennis under the bark. Beetles and fungi may play a role in the life history of these flies. Strongylophthalmyia pengellyi has a flight period from late May to late July with a peak in early to mid-June; S. angustipennis begins flying in early June but continues until September. Comparison of captures using coloured sticky traps suggests superiority of colourless translucent boards.