A new insecticide bioassay for assessing the effects of acute insecticide toxicity on lotic insects was developed. It uses first-instar larvae of a net-spinning caddisfly, Cheumatopsyche brevilineata. The test method was suitable for 30 insecticides with a range of action mechanisms. Caddisfly larvae were much more sensitive than daphnids to neonicotinoids. The new bioassay is thus a useful and reliable method for assessing the impact of chemicals such as neonicotinoids, whose risks for lotic insects might be underestimated by the daphnid bioassay.
2009 Pesticide Science Society of Japan