Temperature-Dependent Functional Response of Spalangia cameroni (Hymenoptera: Pteromalidae), a Parasitoid of Stomoxys calcitrans (Diptera: Muscidae)

The effects of host density, temperature, and burial depths on the functional response of the synovigenic parasitoid Spalangia cameroni (Perkins) attacking pupae of the stable fly Stomoxys calcitrans (L.) were examined. Five temperatures (15, 20, 25, 30, and 35°C), six host densities (2, 4, 8, 16, 32, and 64 pupae per 19.64 cm(2)), and three burial depths in whole wheat grains (0, 8, and 16 cm) were used. It was demonstrated that temperature had a profound effect on the functional response, whereas burial depths of the pupae played a minor role. For all temperatures, the functional response was of type 2 with an upper asymptote that depends on the temperature. Data were fitted by a functional response model where only the maximum attack rate is temperature dependent. The model shows that the optimal temperature for S. cameroni for attacking S. calcitrans pupae is 28.6°C, where the maximum attack rate is 20.2 pupae day(-1). The lower and upper temperature thresholds for attacks were found as 8.1 and 36.6°C, respectively. The temperature range for attacks that resulted in successful parasitism was narrower, namely, 15.0 and 35.5°C. Maximum rate of successful parasitism was estimated to be 18.2 progeny day(-1) occurring at 27.9°C. The proportion of attacks resulting in successful parasitism increased steeply with temperatures >15°C and declined steeply at temperatures >30°C.