CONSPECIFIC SUPERPARASITISM IN 2 PARASITOID WASPS, APHIDIUS-ERVI HALIDAY AND APHELINUS-ASYCHIS WALKER - REPRODUCTIVE STRATEGIES INFLUENCE HOST DISCRIMINATION

Conspecific host discrimination and larval competition in two aphid parasitoid species were studied in the laboratory using the pea aphid, Acyrthosiphon pisum (Harris) (Homoptera:Aphididae), Aphididae), as a host. Aphidius ervi Haliday (Hymenoptera: used internal host cues to discriminate between unparasitized and conspecific parasitized hosts. When only parasitized hosts were available, females oviposited into recently parasitized ones where their progeny had a good chance to survive, but rejected those parasitized greater-than-or-equal-to 24 h earlier where their offspring normally died. Competitions occurred only after both eggs had hatched. Larvae eliminated asychis Walker (Hymenoptera:Aphelinidae), factors, or changes in host internal condition, associated with hatching of the first egg resulted in suppression of conspecific competitors which could be in either larval or egg stage. The older larvae always won competitions through physiological means. A wasp's oviposition decision is shown to be influenced by the probability of its progeny's survival. Species that have different reproductive strategies may respond differently to identical host conditions.