In conclusion, the variation between factors influencing the dose-lethality relation are so numerous, the difference between the lowest and the highest LD50 values can be more than a hundred of times (NRCC, 1981). Consequently, the concept of acute toxicity testing must not be restricted to one determination of the LD50 but extended to many others, reflecting the biotic and abiotic factors of toxicity variation. In the preliminary evaluation of a compound’s toxicity, it is important to establish the dose-lethality relation for the parent molecule and its by-products at three temperatures: internal body temperature for flying (37°C), low wintering bee temperature (12 °C, see Stabentheiner et al., 2003), and one intermediate.

Insect death is not always the best determinant of acute toxicity because the moment of insect death often is imprecise, for example when confused with a severe knock-down that fails to result in death (Moréteau, 1991). For insects, the evaluation of acute toxicity would be more accurate if based on the apparition and intensity of severe clinical signs such as intense trembling, paralysis, feeding or warming inabilities, etc. (Vandame and Belzunces, 1998).