Comparison of Orius insidiosus (Heteroptera: Anthocoridae) and Nabis roseipennis (Heteroptera: Nabidae) as predators of the green cloverworm (Lepidoptera: Noctuidae)

The ability of nymphal and adult Orius insidiosus (Say) to prey upon eggs and early instars of the green cloverworm, Plathypena scabra (F.), was determined in the laboratory. Second instars, 4th instars, adult males, and females of the predator were tested separately on excised soybean leaflets in small arenas. All tested instars and stages of O. insidiosus fed upon eggs and 1st instars of the green cloverworm, with older predators consuming more prey than younger predators. Fourth instars and adults also preyed upon 2nd-instar caterpillars. No stage of O. insidiosus was able to feed upon 3rd instars of the green cloverworm. Using potted soybean plants, we compared the mortality inflicted on eggs and 1st and 2nd instars of the green cloverworm by O. insidiosus and Nabis roseipennis Reuter when the 2 predator species searched alone and in combination. Regardless of prey stage or instar, N. roseipennis consumed far more prey than did O. insidiosus when the predators were tested separately. When the 2 predator species searched for prey together, mortality inflicted by adult O. insidiosus and adult N. roseipennis appeared to be additive; in other combinations of predator stages or instars, combined predation by the 2 predator species did not differ from that observed for N. roseipennis alone. Despite low individual predation rates, O. insidiosus should not be discounted as a potentially important predator of green cloverworm eggs and small larvae in soybean fields, because it is often the most abundant predaceous species associated with this crop