none Enter Cotesia flavipes is an important gregarious larval endoparasitoid of several crambid stem borers, including Diatraea saccharalis. The suitability of two crambid species, Eoreuma loftini and D. saccharalis, pests of sugarcane and rice in Texas, for C. flavipes development was tested. The effect of parasitization by C. flavipes on encapsulation response was assessed in vivo in both D. saccharalis and E. loftini. The results indicated that the parasitoid developed and emerged successfully in D. saccharalis larvae. Although E. loftini larvae were readily parasitized by C. flavipes parasitoids, no wasp larvae hatched from the eggs in this host because eggs were encapsulated by the host's hemocytes. The developmental fate of the E. loftini larvae with encapsulated parasitoids was variable. Most died as abnormal fifth instars or as post-wandering prepupae, while a few developed normally to the pupal stage. In vivo experiments, there was a significant reduction in the percent of beads encapsulated in parasitized larvae in both hosts. However, the percent of beads showing melanization decreased significantly in parasitized D. saccharalis larvae but did not differ significantly in parasitized or unparasitized E. loftini larvae. Our results showed that D. saccharalis is a suitable host for C. flavipes whereas E. loftini is an unsuitable host. This study indicated that lepidopteran stem borers that are taxonomically, behaviorally, and ecologically very similar can differ in their ability to encapsulate a parasitoid species. (C) Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society, 2011. noneEmail20150313 (alialimh@yahoo.com)