Temperature-mediated functional response of Theocolax elegans (Hymenoptera: Pteromalidae) parasitizing Rhyzopertha dominica (Coleoptera: Bostrichidae) in stored wheat

The functional response of Theocolax elegans (Westwood) parasitizing the lesser grain borer, Rhyzopertha dominica (F.) was examined over a range of temperatures. A type II functional response equation was fitted to each temperature regime. The parasitization rate was highest at 301C (20 hosts per day) and was lowest at 201C (2 hosts per day). Handling time was inversely proportional to temperature, and ranged from 1.6 days at 201C to 0.05 days at 301C. Instantaneous search rate also changed with temperature. It was lowest at 201C and highest at 301C. A temperature-mediated functional response equation was fitted to the data, in which handling time was a quadratic function of temperature. The equation explained 74% of the variance in parasitization rate. Theocolax elegans has a narrower optimal temperature range than other parasitic stored-product Hymenoptera. Temperatures greater than 32.51C caused high parasitoid mortality. Published by Elsevier Science Ltd.