Effects of feeding frequency and sugar concentration on behavior and longevity of the adult aphid parasitoid:: Aphidius ervi (Haliday) (Hymenoptera: Braconidae)

Aphidius ervi (Haliday) (Hymenoptera: Braconidae) is a solitary aphid endoparasitoid. Adults feed on honeydew and possibly on other sugar sources such as nectar. Sugar sources can vary qualitatively and quantitatively according to biotic factors and environmental conditions. Experiments were conducted to determine the influence of quantitative variations of sugar sources on survival, feeding behavior. and consumption of A. ervi. A 1:1 glucose-fructose mixture was tested in a range of concentrations (0-70% (w/v)). The lifetime of both sexes increased significantly with increasing sugar concentration. The optimal lifetime was achieved by insects fed with 50 and 70% (w/v) of sugar solution for males and 70% (w/v) for females. Behavioral studies showed that sugar concentrations had a significant influence on feeding duration: for males and females feeding duration increased with sugar concentration. Longevity primarily depended on the concentration of the sugar solution, rather than the quantity of sugar solution ingested. In the last experiment. we studied the effect of feeding intervals on the lifetime of A. ervi females. Females fed with a 50% (w/v) 1:1 glucose-fructose mixture continuously or twice a day lived eight times longer than unfed parasitoids. In contrast, females fed every two days lived only half as long as those fed daily. We can thus conclude that females need at least two food intakes per day to aztain maximum longevity. Our results provide insight into the nutritional requirements of A. ervi under laboratory conditions. Such information can be a basis to improving the longevity of this biocontrol agent by sugar feeding in the field and in greenhouses. (C) 2004 Elsevier Inc. All rights reserved.