A Model for Avoidance of Superparasitism by Solitary Insect Parasitoids

Many solitary parasitic Hymenoptera tend to avoid superparasitism to a varying degree (Salt 1961). Such behaviour reduces egg wastage and will therefore be of selective advantage. Whilst avoidance of superparasitism can be observed directly in the laboratory (Rogers 1972) the extent of such discrimination by insect parasites in the field can often be deduced only from a study of how they distribute their eggs among the available hosts. Egg distributions are, however, the end result of two quite separate processes, search and oviposition, and can be misinterpreted if little is known about either of these features of parasite behaviour. Although the model for parasite egg distributions described here makes certain assumptions about both search and oviposition by female insects, it provides quite a realistic description of the egg distributions of at least twenty-five species of solitary ectoand endo-parasites. The model can also be used to give a rapid estimate of the extent of avoidance of superparasitism by parasites under a variety of laboratory and field conditions.