Predation by the assassin bug Pristhesancus plagipennis (Walker) (Hemiptera : Reduviidae) of Helicoverpa armigera (Hubner) (Lepidoptera : Noctuidae) and Nezara viridula (L.) (Hemiptera : Pentatomidae) in the laboratory

The predatory capacity of the Australian assassin bug Pristhesancus plagipe nnis (Walker) was measured in the laboratory using a predation arena. Each juvenile instar of Helicoverpa armigera (Hubner) and Nezara viridula (L.) w as presented as prey to each P. plagipennis instar to provide a series of p redator/prey combinations. The number of insects killed or eaten by each pr edator instar was recorded for each predator/prey combination. The rate of predation on both prey species increased exponentially with predator develo pment. First- and second-instar P. plagipennis were limited in their abilit y to capture prey larger than second-instar H. armigera and third-instar N. viridula. Third-, fourth- and fifth-instar P. plagipennis were able to pre y on the widest spectrum of prey instars. None of the P. plagipennis nympha l stages were capable of preying on fifth instars of either H. armigera or N. viridula. The data suggest that nymphs of P. plagipennis have the potent ial to be used as an augmentative biological control agent against these pe sts.