EN
A simple index of sensitivity to frost in insects for the general use in ecological studies was introduced. The index is based on a cooling experiment that leads to the estimation of the subzero temperature at which 50% of a sample of particular species life form individuals are killed within 24 hours. By analogy to toxicology, such an estimate was called LTemp₅₀. We present the method using our results from a series of simple cooling experiments conducted on larval gooseberry sawflies Nematus ribesii (Scopoli) and imagine queens, workers and males of the hornet Vespa crabro L. LTemp₅₀ indices were –7.2°C for gooseberry sawfly larvae and ranged from –5.0°C for male hornets to –9.1°C for queen hornets. These differences seem to reflect reasonably the specific thermal environment adaptations of the studied insects.