[Objectives]  To develop a way of accurately, and quickly, distinguishing the sex of Brithys crini pupae and adults, and determine the daily timing of reproductive behavior in this pest. [Methods]  The length, width and weight of pupae were measured and the sex of emergent adults recorded. In addition, the courtship and mating behavior of adults of different ages were studied. [Results]  Female pupae have genital pores on the 8th and 9th ventral segments, and the 8th ventral segment does not heal. The genital pore of male pupae is located on the 9th abdominal segment, and there are obvious semicircular protuberances on either side of the genital pore. Courtship and mating behavior occurred during the dark phase of the photoperiod. Female courtship behavior began 2 hours after dark, and peaked 4 to 8 hours after dark. Females began mating  4 hours after dark, and mating reached its peak 6 to 9 hours after dark. Females began to display courtship behavior at 1 day of age. The older the adult, the lower the mating rate but the longer the mating time. Females could lay eggs in different reproductive states. The life span of adult females was longer than that of males in the same reproductive state. [Conclusion] The sex identification of B. crini pupae could be distinguished by the difference of genital pore. The courtship and mating behaviors are closely related to the age of adults, and there is a certain time coordination between them. The mating behavior could significantly affect the number of eggs and longevity of adults.