Laboratory populations that served as host forAphelinus asychis(Walker) were composed of different combinations of the greenbug,Schizaphis graminum(Rondani); the corn leaf aphid,Rhopalosiphum maidis(Fitch); and the yellow sugarcane aphidSipha flava(Forbes). Although the greatest number of mummies was observed at different temperature and longevity combinations for each species, the same general trend appeared when the number of mummies became large; the number of aphids parasitized increased with increasing temperature to an optimum temperature, and then decreased.A. asychispreferred the greenbug, followed by the corn leaf aphid, and then by the yellow sugarcane aphid.