Diel Periodicities 0f Adult Emergence 0f Chironomidae and Trichoptera from the Delta Marsh, Manitoba, Canada

ABSTRACT

Diel emergence periodicities of adult Chironomidae and Trichoptera were investigated in a shallow bay of the Delta Marsh, Manitoba. Three floating emergence traps were emptied at 2–h intervals over four 48–h periods. Adult chironomids emerged mostly at night in May and June, except Cricotopus intersectus which exhibited a bimodal pattern wilh emergence in the early morning and late afternoon to evening. An increase in diurnal emergence was observed for total chironomids in August. Dicrotendipes nervosus had a nocturnal emergence In May, but had a more random diel emergence periodicity in late August. Procladius denticulatus emerged in the early morning at the beginning of August and in the afternoon at the end of the month. Agraylea multipunctata was the most abundant caddisfly collected. It emerged throughout the day In May and at night to early morning in June.