ANALYSIS OF FORAGING BEHAVIOR OF THE WHITEFLY PARASITOID ENCARSIA-FORMOSA ON A LEAF - A SIMULATION STUDY

Foraging behavior of Encarsia formosa was analyzed with a stochastic s imulation model of the searching parasitoid during a single visit to a tomato leaflet infested with immatures of the greenhouse whitefly, Tr ialeurodes vaporariorum, from which the parasitoid can fly away, The m odel is based on host searching, host selection, host handling, and pa tch leaving behavior and on the physiology of the parasitoid. Outputs of the model were the residence time of the parasitoid on the leaflet and the number of hosts encountered, parasitized, or killed. by host f eeding. The mean residence time and the mean number of encounters, ovi positions, and host feedings on the leaflet increased with host densit y to a maximum of 14.0 h, 209.3 encounters, 15.6 ovipositions, and 2.9 host feedings, The shape of the curves resembles a Type II functional response, The relationship between ovipositions per unit of residence time and host density showed a dome-shaped curve, The most important parameters affecting the number of ovipositions at low host densities were the parasitoid's initial egg load, the walking speed, the walking activity, and the leaf area, At high densities, the maximum and initi al egg loads and the egg maturation rate were most essential. (C) 1997 Academic Press