This study was carried out to improve the rearing methods of endoparasite Hyposoter didymator (Thunberg) for biological control release. The growth and the development of H. didymator on the first, second, and third instars of Spodoptera littoralis (Boisduval) and Helicoverpa armigera (Hübner) under laboratory conditions were investigated. Results indicated that S. littoralis was a suitable host for the rearing of H. didymator. The development time of the parasite on the second instar of both hosts was almost the same (∼17 d). The age of the female parasite affected the percentage of adult emergence, pupal mortality, and females in the offspring reared on S. littoralis host. The best copulation period of H. didymator females and males was 36 h that resulted in 51.8% of females in the offspring. The male to female ratio during copulation period, as well as the presence of males after copulation, and the number of host larvae for each parasite female had no effect on parasitism. Results suggested that S. littoralis second instar is a suitable host for mass rearing of H. didymator parasite, which may improve the use of H. didymator as a biocontrol agent.