Analysis of foraging behavior of the whitefly parasitoid Encarsia formosa (Hymenoptera: Aphelinidae) in an experimental arena: A simulation study

Foraging of Encarsia formosa was analyzed using a stochastic simulation model of the parasitoid's behavior. Parasitoids were allowed to search during a fixed time in an experimental arena with immatures of the greenhouse whitefly, Trialeurodes vaporariorum. The model simulates host searching, selection, and handling behavior and the physiological state (egg load) of the parasitoid. The simulated number of hosts encountered, parasitized, or killed by host feeding agreed well with observations on leaf disks. The hypothesis of random host encounter seems to be correct. The number of ovipositions on the leaf at low host densities was strongly affected by the parasitoid's walking speed and walking activity, the probability of oviposition after encountering a host, and the initial egg load. At high densities, the initial and maximum egg load were most important. A strong temperature effect was found at 18 degrees C or below. The number of encounters, ovipositions, and host feedings increased with host density to a maximum of 25, 6.5, and 1.5, respectively, during 2 h at 25 degrees C. The shape of the curves resembled a Holling Type II, which may be the result of the ''experimental'' procedure, where a parasitoid was confined to a patch during a fixed time.