not in Young Bracon hebetor (Say, 1836) (Hymenoptera: Braconidae) is a gregarious larval ectoparasitoid of several species of pyralids that attack stored products. In this study the protein, lipid and glycogen composition in two host species, Galleria mellonella (Linnaeus, 1758) (Lepidoptera: Pyralidae) and Ephestia kuehniella (Zeller, 1879) (Lepidoptera: Pyralidae), of B. hebetor were examined. The effects of these two host species on protein, lipid and glycogen levels of newly emerged female and male parasitoids were also investigated. The mean levels of protein, lipid and glycogen per host was positively correlated with host size. G. mellonella had much more protein, lipid and glycogen than E. kuehniella. Protein, lipid and glycogen levels in female parasitoids significantly varied with host species. Protein and lipid levels were higher in female parasitoids emerging from G. mellonella than those from E. kuehniella. By contrast, females, reared on E. kuehniella, had much more glyco! gen level than those reared on G. mellonella. No significant difference was detected in protein and glycogen levels of males emerging from two host species. However, males that were reared on G. mellonella larvae had higher lipid level than those reared on E. kuehniella. Ephestia kuehniella (Pyralidae): Host; Galleria mellonella (Pyralidae): Host; Bracon hebetor (Braconidae): Parasite. Bracon hebetor: Carbohydrates, Glycogen levels, Host species effects, host parasite relationships, larva, Lipids, Lipid levels, Proteins, Protein levels, Physiological and biochemical sex differences, Lepidopteran hosts, Ephestia kuehniella, Galleria mellonella; Ephestia kuehniella, Galleria mellonella: Size, host parasite relationships, parasite biochemical composition responses, Hymenopteran parasites, Bracon hebetor. Arthropods; Hymenopterans; Insects; Invertebrates; Lepidopterans. none