Environmental factors affecting longevity, adaptability and diapause termination of Exochomus quadripustulatus L. (Coleoptera: Coccinellidae): A predator of Lepidosaphes ulmi L. (Hemiptera: Diaspididae) on apple

Adults Exochomus quadripustulatus L. were utilized to determine the effect of various environmental factors (mainly temperature) on the longevity, adaptability (hysteresis) and diapause termination either under controlled laboratory conditions or field insectary conditions. Newly enclosed male and female adults E. quadripustulatus from previously field collected pupae were studied for the lifespan of adults under different constant temperatures (15 degree and 20 degree C) and naturally fluctuating (ambient) temperatures using starved (no food), liquid diets (water, and 10% honey solution) and natural prey (mussel scale Lepidosaphes ulmi L.) on apple. Access to distilled water compared to starvation did not increase the longevity of adult but significantly prolonged the life span when honey solution was provided. Longevity in constant conditions and ambient depended on both temperature and food. Coccinellid E. quadripustulatus survived longer time (greater than or equal to 10 months) under field conditions on natural prey L. ulmi than under constant temperature (less than or equal to 4 months). Prey L. ulmi was the best food for survival than 10% honey solution. The degree of adaptability (hysteresis) of adult E. quadripustulatus at alternating temperature regimes (ascending and descending) showed significant differences in feeding at decreasing temperature than increasing ones. The results indicate that, in natural conditions, the adult beetles may be well adapted if they are introduced to different climatic regions where it has not yet been tested. Still more detailed information is to be investigated to prove this hypothesis. Results on diapause termination of female adult E. quadripustulatus showed that temperature did not effect diapause termination under the present experimental conditions. This may be because this species is of univoltine strain in the north-east England.