Physiological costs of cold exposure on the parasitoid Aphidius ervi, without selection pressure and under constant or fluctuating temperatures

The aim of this study is to evaluate the physiological costs and the consequences on fitness of cold exposure on the parasitoid Aphidius ervi (Hymenoptera: Aphidiinae) under non-lethal conditions. We exposed 1-day-old mummies to different treatments: control at 20 degrees C, 7 degrees C constant, 7 degrees C fluctuating (7 degrees C for 22 h and 20 degrees C for 2 h). Two performances of fitness were particularly affected after two weeks at 7 degrees C constant: female longevity and the sex ratio of the progeny was male biased. In contrast, egg load at emergence, lifetime fecundity, frequency of asymmetric individuals in both sexes, and mating success were not significantly affected under all treatments. The effects of these treatments on trends such as utilisation of fat reserves and fertility of males and females are discussed.