none Spodoptera frugiperda; AGE-; HYMENOPTERAN-PARASITES; Chelonus, Cotesia & Microplitis; Parasites interspecific competition, influencing factors; TEMPERATURE-; Hymenopteran parasites interspecific competition relationships Chelonus insularis; LEPIDOPTERAN-HOSTS; Spodoptera frugiperda; Parasites interspecific competition, influencing factors; TEMPERATURE-; Interspecific competition in lepidopteran host, relationships Cotesia marginiventris; AGE-; LEPIDOPTERAN-HOSTS; Spodoptera frugiperda; Parasites interspecific competition, influencing factors; TEMPERATURE-; Interspecific competition in lepidopteran host, relationships Microplitis manilae; LEPIDOPTERAN-HOSTS; Spodoptera frugiperda; Parasites interspecific competition; INTERSPECIFIC-COMPETITION; Chelonus insularis & Cotesia marginiventris; Parasites of lepidopteran host, influencing factors; TEMPERATURE-; Interspecific competition in lepidopteran host, relationships. The effects of host age, age of Cotesia marginiventris Cresson adults and temperature on interspecific competition between fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), larval parasitoids C. marginiventris, Microplitis manilae Ashm. and the egg-larval parasitoid, Chelonus insularis Cresson were studied. All parasitization results for C. marginiventris and M. manilae were from FAW larvae parasitized as eggs by C. insularis. The maximum reproductive potential for C. marginiventris was achieved in hosts initially parasitized by C. insularis and were 36 to 48 hours old and at a temperature of 25 degree C. No host discrimination was found for C. marginiventris between larvae containing a developing C. insularis and non-parasitized larvae. The optimum parasitoid age for C. marginiventris during the host exposure period was 48 to 96 hr.