Multiple Effects of Host Density on Egg Density and the Sex Ratio of Progeny of Bracon hebetor (Say.) (Hymenoptera: Braconidae)

Insect parasitoid optimises their reproductive potential by exploiting host immune system, varying clutch size and progeny sex ratio with reference to the host density. Egg density and the progeny sex ratio of Bracon hebetor Say (Hymenoptera: Braconidae) was studied in relation to the larval density of its host Galleria mellonella (Lepidoptera: Pyralidae). Our findings revealed that parasitoid’s egg density increased with the increase in host density. A comparison was made between egg laying and egg hatching on different host densities and maximum number of egg laying was observed (134.7 eggs) at the highest host densities (16 larvae) while a minimum number of egg laying (15.6 eggs) was registered at lowest host density (one larvae). The egg hatching was decreased due to crowding of eggs laid on host’s larvae and the percentage of adult emergence was also decreased with the increase in crowding of eggs on host’s larvae. It was observed that progeny sex ratio (male/total) increased with the increase in host density. Further dispersion pattern of parasitoid eggs on different host densities were estimated by the Green index. This study has generated novel information on egg laying, egg dispersion and sex ratio of B. hebetor which may lead to the development of sustainable biocontrol programs for lepidopteron insect pests.