Drosophila melanogaster; GENETICS-; New specific gene for cellular resistance to hymenopteran parasitoid; HYMENOPTERAN-PARASITES; Asobara tabida & Leptopilina boulardi; Species specific genes for cellular immune response; IMMUNE-LIKE-REACTIONS; Encapsulation of hymenopteran parasitoids, genetic mechanisms Asobara tabida; Leptopilina boulardi; DIPTERAN-HOSTS; Drosophila melanogaster; Genetic mechanisms of host's species specific immune responses Larvae of Drosophila melanogaster produce a haemocytic reaction against eggs of the parasitoid, Asobara tabida, which leads to the formation of a multicellular capsule surrounding the foreign object. The same phenomenon was observed with the parasitoid, Leptopilina boulardi. Concerning the resistance of D. melanogaster to L. boulardi, a single major segregating locus with the resistant allele dominant to the susceptible one was found. The host strain susceptible to this parasitoid species was found to be highly immune reactive against the eggs of A. tabida. The inheritance of the capacity to encapsulate A. tabida was analysed by comparing reciprocal crosses made using inbred resistant and susceptible parental strains. We conclude that differences in the encapsulation capacity are inherited autosomally, with the reactive phenotype showing complete dominance over the non-reactive one. These data suggest the existence of two independent gene systems, each being concerned with the recognition of one species only. none