The response of the parasitoid C. sonorensis (Cameron) as a natural control agent of the fall armyworm, S. frugiperda (J.E. Smith), was evaluated at 6 host densities and 2 temperature regime. A type-II functional response was exhibited by female C. sonorensis in response to varying densities of all armyworn larvae at both temperatures. Significantly more larvae were parasitized at 25 degree C for the host densities of 60 and 75, than for the same densities of 30 degree C. Third instar fall armyworm larvae were the preferred stage for parasitization by C. sonorensis. none