The effect of size of two host species Galleria mellonella (Pyralidae: Lepidoptera) and Spodotera litura (Noctuidae: Lepidoptera) was studied on larval competition, survival and development of a gregarious ectoparasitoid Bracon hebetor (Say.) (Hymenoptera: Braconidae). The number of adults, sex ratio and size of emerging adults were recorded. Smaller and larger host species were used to determine the survival potential of the wasp. It was observed that maximum number of adult wasps emerged from the hosts G. mellonlla (95 ±2.30 (se) and S. litura (81 ±1.15 (se)) by placing the lowest number of wasp eggs (4 eggs per larvae) on the hosts larvae and minimum number of adult wasps was recorded from the hosts G. mellonella 44 ±1.15 (se), and S. litura (39 ±0.57 (se) by placing the highest number of wasp eggs (20 eggs per larvae) on the hosts larvae. Likewise mean width of the head of adult wasp emerged from G. mellonella was 0.60 mmand S.litura 0.50 mm when 4 eggs were placed on each host larvae, whereas mean head width of developing wasp adults were reduced when 20 eggs had been placed. It may be speculated that due to less availability of nutrient resources, head size of the developing wasp was reduced. It may be concluded that intensity of competition among larvae of B. hebetor affects adult size and development that is directly proportional to the quantity of resources available.
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