Duration of pupal and adult stages of Venturia canescens (Hymenoptera:Ichneumonidae) after exposure of immature stages to high temperatures
Abstract: In this study, the effect of high temperatures on certain biological aspects of thekoinobiont endoparasitoid Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae) wasexamined in the laboratory. Immature life stages of V. canescens (egg, 1st or 2nd instar larva andpupa) were exposed to high temperatures for one hour and the developmental time of pupal stage,as well as the adult longevity was measured. The tested temperatures were 38, 39, 40, 41 and42°C. In all treatments the duration of the pupal stage increased significantly with increasingtemperature. Significantly shorter developmental time of the pupal stage was observed whenpupae of V. canescens were exposed to high temperatures compared to that observed when eggsand 1st-2nd instar larvae were exposed to all testing temperatures except for 42°C. On the otherhand, exposure to high temperatures resulted in a decrease of adult longevity. When 1st or 2ndinstar larvae and eggs of V. canescens were exposed to 40°C for one hour adult longevitydecreased to 4.2 and 6.2 days, respectively. However, when pupae of V. canescens were exposedto high temperatures the adult longevity was significantly longer than that observed when eggsand 1st or 2nd instar larvae were exposed to high temperatures and it ranged from 10.2 to 13.4days. Our results suggest that high temperatures on immature stages had a negative effect onduration of pupal stage and adult longevity. These findings are of great importance for a betterunderstanding of the effects that high temperatures have on V. canescens.