The quality of the mass reared insects plays a crucial role in effective operation of radiation mediated inherited sterility (IS) programme, proposed to suppress the lepidopteran pest Spodoptera litura (F.). In this context, the low dose of ionizing radiation (LDIR) was assessed to have any stimulatory effect on the reproductive behaviour of male moths treated as 0-1 day old egg, third instar larva (L3) or 2-3 days old pupa. Radiation hormesis was observed in the mating success of males treated at 0.75 Gy and 1 Gy in both egg and L3 stages. Invitro sperm activation assay indicated more sperm activity during peak plateau phase in moths derived from treated egg (0.75Gy, 1 Gy) and treated L3 (1 Gy). These findings implicit beneficial effect on sperm activity and mating success of male S. litura, which might further improve mating competitiveness of male moths to be used in IS technique.