Three gregarious, endoparasitic braconids, a Kenyan strain of Cotesia sesamiae, and the exotic Cotesia flavipes and Cotesia chilonis were imported into Benin as candidates for biological control of stem- and cob borers of maize and stemborers of millet. Host acceptability and host suitability of six gramineous borers occurring in western Africa, the noctuids Sesamia calamistis, Sesamia poephaga, Busseola fusca, the crambid Coniesta ignefusalis, and the pyralids Eldana saccharina and Missidia nigrivenella, to these parasitoids were evaluated to test the hypothesis that new associations were superior over old association parasitoid-host relationships. All hosts were accepted by all Cotesia spp., except M. nigrivenella, which was not attacked by C. chilonis. Parasitoid progeny developed successfully in S. calamistis, S. poephaga and C. ignefusalis. S. calamistis was the most suitable host in terms of duration of developmental time, brood size and mortality of parasitoid progeny. It was concluded that because of its host specificity, the old association parasitoid C. sesamiae would have the highest chance of establishment in cereal systems in West Africa. BR Animals and man. Control. Parasites diseases and disorders. Parasites. Insect parasites. Hosts. Insect hosts. Habitat. Man made habitat. Zoogeography. Dispersal. Means of dispersal. Land zones. Afrotropical region. Cotesia chilonis (Braconidae): Parasite; Cotesia flavipes (Braconidae): Parasite; Cotesia sesamiae (Braconidae): Parasite; Busseola fusca (Noctuidae): Host; Sesamia calamistis (Noctuidae): Host; Sesamia poephaga (Noctuidae): Host; Coniesta ignefusalis (Pyralidae): Host; Eldana saccharina (Pyralidae): Host; Mussidia nigrivenella (Pyralidae): Host. Busseola fusca, Coniesta ignefusalis, Eldana saccharina, Mussidia nigrivenella, Sesamia calamistis, Sesamia poephaga: Biological control, host suitability, parasite introduction, Hymenopteran parasites, Cotesia chilonis, Cotesia flavipes, Cotesia sesamiae, Cultivated land habitat, Cereal systems, Africa, West Africa; Cotesia chilonis, Cotesia flavipes, Cotesia sesamiae: Biological control, host suitability, Lepidopteran hosts, Busseola fusca, Coniesta ignefusalis, Eldana saccharina, Mussidia nigrivenella, Sesamia calamistis, Sesamia poephaga, Cultivated land habitat, Cereal systems, Introduction, Africa, West Africa. ST Animalia, Arthropoda, Insecta, Hymenoptera, Apocrita, Terebrantia, Ichneumonoidea, Braconidae; Animalia, Arthropoda, Insecta, Lepidoptera, Glossata, Heteroneura, Noctuoidea, Noctuidae; Animalia, Arthropoda, Insecta, Lepidoptera, Glossata, Heteroneura, Pyraloidea, Pyralidae. Arthropods; Hymenopterans; Insects; Invertebrates; Lepidopterans. none