A Simulation Model of Spatial Heterogeneity and Non-Random Search in an Insect Host-Parasitoid System

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Abstract
A population model of the interactions between insect parasitoids and hosts in a patchy environment is proposed. The searching behavior of an individual parasitoid is described as a simple innate response to host and parasitoid associated stimuli. The probability of a given response being elicited by a given stimulus apparently varies with an individual''s current rate of oviposition. The model includes the following behavioral responses of the parasitoid: a functional response to the host density of a patch; a response to other parasitoids encountered on a patch; an aggregative response caused by the individual parasitoid being attracted more often to the favorable patches and spending more time on them than on less attractive patches; and a response to previously attacked hosts. The model predicts the number of parasitoids and parasitized hosts to be found on the different host patches and the number of parasitoids in transit between the patches. The model is used to simulate the dynamics of a laboratory host-parasitoid system consisting of the ichneumonid Nemeritis canescens Grav. and larvae of the moth Ephestia cautella. The simulations show that the model accounts very well for the observed adaptive behavior of Nemeritis.