A Model for the Functional Response of Parasitoids

A mathematical model is developed to describe the functional response of parasitoids that imperfectly avoid superparasitism.This new model contains older models as special cases.It is satisfactorily fitted to the measured response of a laboratory parasitoid-host system. DEFINITIONSParasitoids are insects requiring a host for the development of their larvae.The free-living adult females search for hosts and oviposit in or near them.When the eggs hatch, the larvae feed on the hosts, causing at first little damage, but gradually attacking more vital parts and eventually killing the host.Most parasitoids belong to two orders (Diptera and Hymenoptera) and they make up about 14% of the known insect species.Some of them are specific while others attack a variety of hosts species.Hosts belong to almost all insect orders, eggs, larvae, and pupae being far more frequently attacked than adults.Other species than insects can also be parasitized (spiders, snails).Parasitoids are called solitary if one larva only can develop in a given host, gregarious if several larvae can develop in a same host.Solitary species (e.g.most Ichneumonidae) normally lay a single egg at each oviposition.Gregarious species (e.g.most Braconidae and Chalcidoidea) usually lay a batch of eggs corresponding to the host's capacity (up to several hundreds, even thousands) (BERLAND 1976).