Phenology and Ecology of Some Trichoptera in a Low-Gradient Boreal Stream

Abstract

Nine species of caddisflies (seven species of Leptoceridae, Helicopsyche borealis and Molanna flavicornis) were univoltine in a stream near Edmonton, Canada. Neureclipsis bimaculata was bivoltine at this site. No evidence of egg or adult diapause was seen among the ten numerically dominant species, although four species apparently overwintered as dormant larvae. No obvious increase in mortality was associated with overwintering. Emergence of the ten species occurred during the June to August period. Analysis of literature records of adult collections revealed significant relationships between date of first capture and latitude, and duration of the capture period against latitude for H. borealis and Oecetis inconspicua. Most of the species were found in association with macrophytes, especially Chara and Potamogeton richardsonii. Macrophytes were important as attachment sites for pupal cases, for dormant overwintering larvae, and for the filtering nets of the net-spinning species. Macrophytes may also be important as sources of food, either directly or by providing substrata for periphyton growth.