Parasitoid diets: Does superparasitism pay?

The ability of insect parasitoids to discriminate between parasitized and unparasitized hosts is well documented. Despite this, hosts that have been parasitized more than once are frequently found, an occurrence known as superparasitism. Since superparasitism results in interlarval competition, it was generally assumed to be caused by discriminatory 'mistakes'. Recently, theoretical studies have suggested that under certain circumstances superparasitism can be optimal. Superparasitism can thus be viewed as an active foraging strategy rather than as a passive process. Because parasitoids show a direct link between foraging success and reproductive output, they afford important opportunities to test evolutionary models of behaviour.