Competition for space by predators in streams: field experiments on a net‐spinning caddisfly

Abstract

SUMMARY. 1. Field experiments in a fishless stream were carried out on an abundant caddisfly with a predatory, net‐spinning larva, Plectrocnemia conspersa (Curtis), to assess whether net site availability affects their microdistribution. 2. Net sites were supplemented by adding nought, one or four artificial structures to replicated patches on the stream bed. In each of three experiments at different seasons (summer, autumn and late winter), caddis densities increased significantly in patches with extra net sites. 3. The response of caddis to supplemented net sites could be affected by the subsidiary effects of food and offish. These potential interactions were assessed in each experiment by..