Effect of Host-feeding on Reproduction in Ooencyrtus nezarae (Ishii) (Hymenoptera: Encyrtidae), an Egg Parasitoid of the Bean Bug Riptortus clavatus

The egg parasitoid Ooencyrtus nezarae is a candidate for biological control of several hemipterans that are important pests of beans, including Riptortus elevates. However, many aspects of the reproduction in O. nezarae remain unknown. The present study highlighted factors affecting the reproduction of O. nezarae. When given honey, adult females lived around 40 days, regardless of the presence or absence of the host eggs, or of the age of host eggs. When given honey and young host eggs, females parasitized, on average, around 20 host eggs and produced 75.1 offspring wasps during the lifetime. However, the lifetime offspring production was only 11.2 when 7-day-old host eggs had been given. Female O. nezarae was a concurrent host feeder and fed on host hemolymph before oviposition. Although female O. nezarae emerged with no mature eggs, they quickly began maturing eggs after emergence, carrying ca. 15 mature eggs within a week. However, the number of mature eggs in the ovary gradually decreased from 15 clays after emergence, and 30-day-old females had only 5 eggs, indicating the occurrence of egg resorption in old females. Then, the effect of host feeding on the egg maturation was examined. Although access to host itself caused an increase of egg load of females, manipulation experiments confirmed that host, feeding stimulated egg maturation and that female produced ca. 2 additional eggs via a single host. meal. The importance of host age and host-feeding in O. nezarae reproduction was discussed.