SPIDER VENOM AND ECOETHOLOGICAL IMPLICATIONS - A SIMPLE MATHEMATICAL-MODEL

We present a model describing the mortality of prey items when a series of them is bitten by a single spider, which thus can inject venom in each one of them. Prey mortality is assumed to be linearly and negatively correlated to prey size and to prey position within the series. This assumption is in good agreement with experimental data obtained by Boeve (1994) with the free-hunting and generalist spider Cupiennius salei. Based on our model, a theoretical prey yield expresses the hunting ability of the spider. This yield is a function linear in prey position and quadratic in prey size. We suggest that during the evolution of spiders venom has favoured an increase in prey size rather than in the number of prey items. We discuss how prey yield could be related to amount and to quality of the venom.