INTERFERENCE AND THE IDEAL FREE DISTRIBUTION - OVIPOSITION IN A PARASITOID WASP

The interference ideal free distribution (IFD) model of Sutherland mak es a number of predictions that have yet to be tested and that have im plications for the validity of subsequent extensions to the theory. We tested these predictions in a study using different densities of the parasitoid wasp, Venturia canescens, foraging on patches containing di fferent densities of its host, Plodia interpunctella. Our results supp ort a number of the interference IFD model's general predictions. Gain rate decreased because of increased interference at higher density. A lthough gain rates on the two patches differed slightly, this would be expected allowing for some sampling behavior and perceptual constrain ts. Early in each experiment when patch assessment is likely to occur, wasp movement was higher and gain rates lower. However, the more spec ific prediction of Sutherland's model, that proportional patch use sho uld be constant and independent of density, was not upheld. Contempora ry IFD models use only one of several equally valid potential relation ships between gain rate, interference, and competitor density. The res ults of this study provide support for the additive model developed by Tregenza et al. (companion article).