none Heliothis; HYMENOPTERAN-PARASITES; Microplitis croceipes; Parasitism rate & female progeny production, parasite age relationship Microplitis croceipes; AGE-; Parasitism rate & female progeny production relationships; FECUNDITY-; Female progeny production peak; LEPIDOPTERAN-HOSTS; Heliothis; Female progeny peak & parasitism rate, age relationship, laboratory study Age-dependent parasitization and production of female progeny by adult females of Microplitis croceipes (Cresson), a parasitoid of Heliothis virescens F. and Helicoverpa zea (Boddie), were determined under laboratory conditions at a constant temperature of 30 +- 1 degree C. M. croceipes females (n=22) parasitized 186.8 +- 36.9 (mean +- SD) hosts and had a longevity of 11.5 + 1.7 d. The mean daily parasitization (ranging from 0.05 to 24.0 hosts/day) and production of female progeny (ranging from 0 to 14.7 females/day) were inversely related to the females' age from 6-d old until death. The range in female age of peak parasitization, from 2 to 6 d of age of the females, coincided with that of peak production of female progeny. These results indicate that M. croceipes females should be released at this peak reproductive period in order to achieve maximum effect in a program for management of H. virescens and H. zea.