【目的】 明确外源褪黑素对草地贪夜蛾Spodoptera frugiperda过冷却点和结冰点的影响。【方法】 利用食物介导法对草地贪夜蛾1-6龄幼虫饲喂含有不同浓度（0、0.2、2、20和200 µg/g）外源褪黑素的人工饲料，测定褪黑素处理后草地贪夜蛾各虫态的过冷却点和结冰点变化。【结果】 外源褪黑素处理后，草地贪夜蛾3-6龄幼虫、雌雄蛹和成虫的过冷却点和结冰点与对照相比均显著降低（P＜0.05），表明外源褪黑素处理有助于增强草地贪夜蛾的抗寒性。随着外源褪黑素处理浓度的升高，草地贪夜蛾各虫态的过冷却点和结冰点与对照相比显著降低（P＜0.05），尤其在200 µg/g浓度处理下，草地贪夜蛾各虫态的过冷却点和结冰点最低。雌、雄性两性个体间过冷却点和结冰点具有一定差异，雌虫过冷却点和结冰点略低于雄虫，而且外源褪黑素处理能进一步增强雌、雄个体对低温环境的适应能力。【结论】 外源褪黑素处理能降低草地贪夜蛾的过冷却点和结冰点，增强草地贪夜蛾的抗寒性。

 [Aim]  To clarify the effect of exogenous melatonin on the supercooling and freezing points of Spodoptera frugiperda. [Methods]  Using the food-mediated method, the 1st-6th instar of fall armyworm(S. frugiperda) larvae were fed an artificial diet containing different concentrations (0, 0.2, 2, 20, and 200 µg/g) of exogenous melatonin after which their supercooling and freezing points were measured and compared. [Results]  Ingesting exogenous melatonin significantly reduced the supercooling and freezing points of 3rd to 6th stage larvae, pupae and adults, compared to the control, indicating that exogenous melatonin enhances the cold resistance of S. frugiperda. Increasing the exogenous melatonin concentration significantly lowered the subcooling and freezing points of each age class relative to the control group (P < 0.05). The lowest subcooling and freezing points for each age class were measured at an exogenous melatonin concentration of 200 µg/g.The males of S. frugiperda exhibited slightly higher supercooling points and freezing points than females. [Conclusion]  Exogenous melatonin can lower the supercooling and freezing points of S. frugiperda, thereby enhancing its cold hardiness.