Chronic effects of short-term contamination with the pyrethroid insecticide fenvalerate on the caddisfly Limnephilus lunatus

Larvae of the caddisfly Limnephilus lunatus Curtis were exposed to the pyrethroid fenvalerate for one hour and transferred to artificial outdoor stream systems, where their survival rate and emergence were monitored over 84 days. Lethal effects of the pyrethroid almost always appeared shortly after the short-term contamination, but chronic influences were also observed. At a concentration of only 0.01 mu g l(-1) a slight increase in mortality over the entire period of observation, as well as a delay in development and hence in emergence occurred. Such reactions under field conditions may impair the survival of this species, and sublethal effects of brief pyrethroid contamination, previously largely ignored, can have important consequences for aquatic macroinvertebrates.