PYRALIDAE-; HYMENOPTERAN-PARASITES; Cotesia flavipes; Host selection & reproductive success, worldwide; LAND-AND-FRESHWATER-ZONES; Host selection & reproduction, geographic variation Cotesia flavipes; REPRODUCTIVE-PRODUCTIVITY; Reproductive success; VARIATION-; Lepidopteran host selection & reproductive success, worldwide variation; LEPIDOPTERAN-HOSTS; Pyralidae; Host selection & reproductive success, geographic variation, worldwide; LAND-AND-FRESHWATER-ZONES; Geographic variation in lepidopteran host selection & reproductive success Local parasitoid populations may be adapted to their sympatric major plant host complex. Parasitoid strains may thus differ in their propensity to search for a particular micro-habitat or host or they may differ in their physiological compatibility with particular plant or host species. Cotesia flavipes Cameron, a larval parasitoid used worldwide in biological control against tropical stemborers, has a wide host range in diverse habitats. The existence of plant and/or host specific strains in C. flavipes has been postulated. To provide insight into the existence of strains in C. flavipes, we compared the plant/ host complex selection behaviour, and physiological compatibility with different stemborers, of six different geographic strains of C. flavipes that differed in the plant/host complex they were obtained from. The results of the host selection experiments indicate that there is no intraspecific variation in host selection behaviour among C. flavipes strains. However, our comparative experiments show variation in reproductive success among strains. The most significant result was that the strain with the longest period of co-existence with the new host Diatraea saccharalis Fabricius had the highest reproductive success on this host species. We argue that the reported existence of C. flavipes strains is based not on differences in host selection behaviour, but on differences in physiological compatibility between local parasitoid and host population.