Screened potted cactus, Opuntia ficus-indica (L.) Mill., plants containing pairs of adult male and female cactus moths, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), were placed in a cactus field in St. Marks, FL, to measure oviposition patterns under ambient conditions. Results showed a narrow window for oviposition during third and sixth day of adult female's life. Peak oviposition activity occurred on the third day, whether measured in total fecundity, numbers of eggs per egg stick or numbers of ovipositions. After the third day, not only did oviposition rate decrease but also the quality of eggs produced declined. Percentage of egg hatch decreased and egg incubation increased. Longevity of adult males (6.3 ± 0.79 d) did not differ from that of females (5.2 ± 0.4), although female adults (157.8 ± 4.5 mg) weighed more than males (74.9 ± 1.51). Therefore, from the perspective of mass rearing this moth, the optimal time for collecting eggs is limited to the third day in the life of the adult female.