Mating by the fall armyworm,Spodoptera frugiperda(J. E. Smith), was studied in the laboratory. With the night cycle beginning at 2100 hours, 73–84% of the matings occurred between 2200 and 0300 hours. However, mating pairs were observed throughout the night. Most matings (80%) lasted longer than 45 min. Mean duration of mating averaged 130 min. Based on the number of spermatophores in the bursa copulatrix of mated females, female moths mated a mean of 3.7 times (range, 0–11) during their life span. Males mated a mean of 6.7 times (range, 0–15) during their life span. Matings by males were most frequent during the first three nights after their emergence. Although males mated throughout most of their adult life, the incidence of mating declined as the moths aged. The number of matings peaked at 25 and 30°C, with little mating at 10 or 15°C.