Effect of Host Density on the Progeny Production of the Egg Parasitoids Ooencyrtus nezarae (Ishii) (Hymenoptera : Encyrtidae)

Abstract

The effects of host density on progeny production, clutch size and sex ratio of Ooencyrtus nezarae, an egg parasitoid of the bean bug Riptortus clavatus, were examined to determine the optimal host provision condition in which mass-rearing efficiency of the parasitoid is maximized. Female parasitoids allocated prog- eny in regard to host density so as to avoid laying more eggs than the host can support. The maximum prog- eny production and parasitism rate occurred when 5 host eggs were given everyday throughout the life time. However, if we continuously provided with hosts for ten consecutive days, the progeny production with one host per day was more consistent than that with five hosts per day. Female O. nezarae reduced the clutch size if the host density was beyond five. However, the overall progeny sex ratio remained constant regardless of the host density. The results suggested that the excessive exposure of the host to O. nezarae wouldn't affect the reproductive fitness, but would reduce the reproductive potential of this parasitoid, which can in turn affect the efficiency of mass rearing perspective.