Cotesia flavipes is a parasitoid that develops gregariously in several stemborer species (Lepidoptera: Pyralidae) such as Diatraea saccharalis. Parasitism induces host immunosuppression by the actions of the wasp’s polydnavirus (PDV) as illustrated by the host-parasite relationship between Manduca sexta and Cotesia congregata. Parasitization of M. sexta, a non-pyralid species, by C. flavipes results in host developmental arrest and disruption of pupal development. Encapsulation and melanization of the parasitoid eggs is invariably observed in M. sexta hence the C. flavipes PDV may not able to suppress the host’s immune response. Third and fourth larval host instars were selected by the female wasps which had variable fates in host larvae/pupae. Defects in pupal stages were observed and moths failed to eclose to the adult stage. Transplantation of parasitoid larvae into non-parasitized surrogate hosts yielded encapsulation in M. sexta without parasitoid larvae emergence. The host-parasite system of C. flavipes and M. sexta could be an alternative system for studying immune responses of refractory hosts.