TEMPERATURE-DEPENDENT FUNCTIONAL-RESPONSE OF THE PARASITOID CEPHALONOMIA-WATERSTONI (GAHAN) (HYMENOPTERA, BETHYLIDAE) ATTACKING RUSTY GRAIN BEETLE LARVAE (COLEOPTERA, CUCUJIDAE)

The effects of host density and temperature on the functional response of the bethylid parasitoid Cephalonomia waterstoni (Gahan) attacking fourth-instar rusty grain beetle, Cryptolestes ferrugineus (Stephens) were examined. Five temperatures and six host densities were used. A type II functional response model was fit separately to each temperature. The maximum attack rate ranged from 7.5 larvae/12 h at 25-degrees-C, to 2.9 larvae/12 h at 38-degrees-C. Handling time and instantaneous search rate varied with temperature. A new functional response equation was developed in which handling time is a quadratic function of temperature. This equation explained 83% of the variation in attack rate. Although instantaneous search rate was also affected by temperature, it was sufficient to make only handling time a function of temperature because the two parameters were highly correlated.