Abstract: 【Aim】 Protandry was more common in studies on developmental duration of sex dimorphic insects, and protogyny was less reported. The fall armyworm, Spodoptera frugiperda is a severe migratory pest on maize, and there is a phenomenon of protogyny in its developmental duration. The purpose of this study is to clarify the stability of this phenomenon and explore its influencing factors, so as to provide a theoretical basis for the accurate monitoring and early warning of S. frugiperda.【Methods】 The growth and development of S. frugiperda under three photoperiods (16L∶8D, 14L∶10D and 8L∶16D) and three food conditions (maize leaves, peanut leaves and artificial diet) were analyzed, and the ovaries of S. frugiperda reared under different photoperiods and food conditions were dissected. Moreover, the growth and development of Mythimna separata, S. litura and S. frugiperda in Noctuidae were compared to evaluate whether the protogyny was the commonness of Noctuidae insects with migratory habits.【Results】 In the comparison of three Noctuidae migratory insects, only the female adults of S. frugiperda eclosed significantly earlier (1.28 d ahead) than the male adults, and the eclosion phenomenon was stable under different photoperiods and food conditions, and only showed a weakening trend when S. frugiperda fed on peanut leaves. It was found that the ovaries of the newly eclosed adults of S. frugiperda were always immature under different photoperiods and food conditions, and did not change with external conditions. The development of female pupa of S. frugiperda was significantly faster than that of male pupa, which was the main reason for the difference in eclosion time between the two sexes of S. frugiperda, and the difference was positively correlated with the pupal weight of the two sexes: Compared with the female pupal weight, the male pupal weight of S. frugiperda increased significantly by 9.88%.【Conclusion】 The phenomenon of protogyny of S. frugiperda is relatively stable. Photoperiod and food will not change this phenomenon, but will affect the difference of eclosion time between the two sexes, and protogyny is not the commonness of Noctuidae insects with migratory habits.

Key words: Spodoptera frugiperda; protogyny, pupal weight, photoperiod, food, growth and development