not in Young Seven age classes from late first to fourth instars of Spodoptera littoralis larvae were singly parasitized by Microplitis rufiventris Kok. to study changes in diameter of maturing teratocytes at the completion of parasitoid development. The largest cell diameter was observed when hosts were parasitized in their fourth instar compared with parasitization on younger hosts. The diameter of mature teratocyte cell was instar-dependent. The results suggest that the teratocytes may be involved in active absorption of some host material(s) from the surrounding haemolymph of the parasitoid. BR Reproduction. Parasites diseases and disorders. Parasites. Insect parasites. Hosts. Insect hosts. Microplitis rufiventris (Braconidae): Parasite; Spodoptera littoralis (Noctuidae): Host. Microplitis rufiventris: Egg, Teratocytes growth, Lepidopteran hosts, Spodoptera littoralis; Spodoptera littoralis: Hymenopteran parasites, Microplitis rufiventris. ST Animalia, Arthropoda, Insecta, Hymenoptera, Apocrita, Terebrantia, Ichneumonoidea, Braconidae; Animalia, Arthropoda, Insecta, Lepidoptera, Glossata, Heteroneura, Noctuoidea, Noctuidae. Arthropods; Hymenopterans; Insects; Invertebrates; Lepidopterans. none