none Three Aphidius spp. parasitoids of the lucerne aphids, pea aphid (PA) and blue green aphid (BGA), were introduced into New Zealand from 1977 to 1982. A. eadyi spread rapidly and now occurs in all the main lucerne-growing areas. In comparison, A. ervi was difficult to establish, failing to persist after several initial recoveries, but was eventually established from release of separate strains in the North and South Islands, replacing A. eadyi as the predominant parasitoid in the North Island. Despite large releases, A. smithi has not established. A. ervi shows a preference in the field for BGA, but in the laboratory it demonstrated the ability to adapt from PA to BGA in two generations. Laboratory experiments showed that A. eadyi has a higher fecundity and faster development rate than A. ervi indicating that it competes better for PA. Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Land and freshwater zones; Australasian region Aphidius eadyi; Aphidius ervi; Aphidius smithi (Braconidae ); Hemipteran hosts; Acyrthosiphon kondoi & A. pisum; Release & establishment in host; New Zealand; Release & establishment in hemipteran hosts Acyrthosiphon kondoi; Acyrthosiphon pisum (Aphidoidea ); Hymenopteran parasites; Aphidius eadyi; A. ervi & A. smithi; Parasite release & establishment in host; New Zealand; Hymenopteran parasite release & establishment in host