Abstract: 【Aim】 The diamondback moth, Plutella xylostella, is a cosmopolitan lepidopteran pest that mainly attacks cruciferous plants. Its strong reproductive capacity is one of the main reasons why it becomes the pest most difficult to control in the field. Mating is a physiological process necessary for the bisexual reproduction of most insect species. Clarifying the mating behavior and physiological response of female and male adults is of great significance for population monitoring and control of P. xylostella. 【Methods】 The gonad and spermatophore formation of P. xylostella adults were observed anatomically. The mating and remating capacity, spermatophore formation and digestion of P. xylostella adults, and the effects of mating frequency on the spermatophore formation and female fecundity were measured and analyzed by behavioral and biological experiments. 【Results】 During the mating process, the seminal fluid of male adults of P. xylostella was transferred to female adults in the form of spermatophore, which is a white, opaque, balloonlike structure within the bursa copulatrix. The spermatophore could be sufficiently digested and absorbed after mating. The observation results of mating capacity showed that both female and male adults of P. xylostella had multiple mating behaviors. After the first mating, for the male adults there was a short delay in re-mating, and the mating success rate was 54.6% within 20 min, which was significantly lower than that of the first mating. Although the multiple mating did not affect the mating duration of male adults, the mating history significantly inhibited the spermatophore size and female fecundity. There was an obvious re-mating inhibition in mated female adults, of which the mating rate was significantly lower than that of the unmated females within 12 h, suggesting that re-mating inhibition depends on the rates of spermatophore digestion and absorption after the first mating. There was no significant difference in the oviposition amount and egg hatching rate between female adults with multiple and single mating. 【Conclusion】 Multiple mating results in delayed and inhibited re-mating of female and male adults of P. xylostella, respectively. The spermatophore produced by male adults with multiple mating is significantly reduced, and the oviposition amount and egg hatching rate of female adults get no benefit from multiple mating. This study provides a theoretical foundation for better understanding the reproductive regulation mechanism of P. xylostella.

Key words: Plutella xylostella, mating behavior, spermatophore, fecundity, physiological response