Feeding ecology of three species of Hydropsyche (Trichoptera: Hydropsychidae) in southern Ontario

Abstract

Food habits and net-spinning activity of Hydropsyche betteni, Hydropsyche slossonae, and Hydropsyche sparna were examined over 1 year at three stations in the Humber River, Ontario. Hydropsyche slossonae and H. sparna nets were similar in mesh size; H. betteni net meshes were much smaller; however, the H. betteni net had the greatest total surface area. Differences in retreat design may relate to prey specialization and (or) flow pattern.Gut content analysis indicated seasonality in food types ingested. Animal material in guts increased in spring and continued to be important in summer; but it decreased in fall and, except in H. betteni, remained low during winter. In winter, no nets were constructed yet larvae continued to feed on epilithic material from the substrate.Food habits were more similar between species in third instars than in later instars, and later instars usually contained more animal material and less detritus than third instars. The most significant difference between species was the degree of carnivory, H. betteni being more carnivorous than the other species at two of the three stations. Avoidance of the filamentous diatom Melosira sp. and inorganic material, which at times were abundant in the environment, suggested some degree of food selectivity.