FOOD SEARCHING AND SUPERPARASITISM IN SOLITARY PARASITOIDS

Optimality theory predicts that, provided that a larva resulting from superparasitism has some chance of winning the competition with the ot her larvae present in the host, under certain conditions, solitatry pa rasitoids should resort to superparasitism. Both theoretical and exper imental studies have shown that the life expectancy of the parasitoid has a strong influence on the decision to reject or to accept superpar asitism. In many species, life expectancy on its turn depends on the f eeding behaviour of the parasitoids, which have to forage for non-host food (mainly plant materials), for the maintenance of their energy re serves. As many solitary parasitoids do not find non-host food in thei r host patches, they have to choose at each instant whether to search for food or to search for hosts. In this paper, we develop a stochasti c dynamic programming model to study the behavioural choice between ho st and food searching, and its consequences for the acceptance and rej ection of superparasitism. We study the influence of habitat quality a nd parasitoid physiological state on the optimal choice. The model pre dicts that the crucial point determining the optimal strategy is the b alance between egg-and time-limitation.