The differences in the reproductive biology of overwintered (OW) and F-1 generation of Trissolcus semistriatus Nees and T. festivae Victorov (Hymenoptera: Scelionidae) were investigated under laboratory conditions. The experiments were conducted to evaluate oviposition period, lifetime fecundity, female progeny, sex ratio, and longevity of OW and F-1 generation with the two species as factors. The results of this study showed that the oviposition period of F-1 generation was longer than that of OW females for both of the two parasitoid species. With the exception of F-1 generation of T. festivae, the highest daily average progeny production of females was recorded on the first day. The mean lifetime fecundity of ovipositing females were calculated as 88.8 +/- 6.13 and 111.9 +/- 6.66 for OW and F-1 generation of T. semistriatus, 85.6 +/- 6.83; 104.7 +/- 4.66 for OW and F-1 generation of T. festivae, respectively. The sex ratios of progeny for both of the species were distinctly female-biased. The effects of species, factors (OW and F-1 generation), and their interactions were significant on the sex ratio of progeny. The average longevity of OW females was 16.2 +/- 1.76 days for T. semistriatus and 16.9 +/- 1.21 for T. festivae. The average longevity of F-1 generation females was 17.5 +/- 1.46 days for T. semistriatus and 28.5 +/- 1.94 for T. festivae. Thus, some several biological characteristics of both species were compared and discussed with regard to the use of OW populations for the successful implantation of biological control and mass production.