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 out door stream systems, where their survival rate and emergence were moni tored over 84 days. Lethal effects of the pyrethroid almost always app eared shortly after the short-term contamination, but chronic influenc es were also observed. At a concentration of only 0.01 mu g l(-1) a sl ight increase in mortality over the entire period of observation, as w ell as a delay in development and hence in emergence occurred. Such re actions 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 macroinve rtebrates.