Sperm behavior represents one of the attributes in the radiogenetic technique called inherited sterility crucial for its effectiveness to suppress populations of Spodoptera litura (F.) (Lepidoptera: Noctuidae). Quantitative and qualitative assessments of S. litura sperm behavior (production, descent, activation, movement and transfer to females) were made in parental (P) males that received sub-sterilizing irradiation doses of either 100 or 130 Gy and in their F₁ generation males. Age dependent production of eupyrene and apyrene spermatozoa in the testes were not affected by such irradiation in the P males, nonetheless a slight but significant effect occurred in the F₁ generation. During the rhythmic cycles of sperm descent in the photophase and scotophase, the profile and proportion of sperm descent from the testes to the upper vas deferens (UVD), seminal vesicle (SV) and duplex were not significantly influenced by irradiation in P and F₁ males. Sperm activation—assessed as percent active apyrene sperm and their intensity of motility—was not diminished in irradiated P males, while in F₁ males it showed a slight but significant reduction. Mating status was not a markedly pronounced factor in eliciting the motility of irradiated sperm. Sub-sterilized P males and their F₁ progeny were nearly as competitive as non-irradiated males in terms of sperm transfer from male to female. Successful amphimixis occurred between the altered genomes of either irradiated P males or F₁ males and the non-irradiated female genome; consequently dose dependent reductions in percent egg hatch were observed in the hatching of F₁ and F2 eggs. Irradiation with either 100 or 130 Gy did not adversely influence the sperm characteristics in the irradiated P males and their F₁ male progeny, and this study validated the sperm' viability and performance in irradiated P males and of their F₁ sons. The findings indicated that these genetically altered sperm would fertilize the eggs of wild females and lead to effective control of this tropical pest.