【目的】明确云南南部周年繁殖区草地贪夜蛾Spodoptera frugiperda常年发生动态和虫源组成。【方法】 运用高空灯自动诱集装置对2020年云南南部江城和元江两地草地贪夜蛾种群的上灯行为节律进行逐时系统监测，依据灯下种群动态和上灯行为节律，并结合气象条件和昆虫轨迹分析模型推断虫源分布。【结果】 云南南部周年繁殖区均可诱集到草地贪夜蛾成虫，存在多个发生盛期（3-4月、6-10月）。该区域草地贪夜蛾发生动态复杂，不同季节灯下本地虫源和迁入虫源组成比例存在差异。1-2月主要为本地迁出虫源且低温无法向北迁出；3-4月既有本地迁出又有境外迁入，迁出可能降落地为贵州和广西等地，境外迁入虫源则主要分布在缅甸东南部；5-7月江城后半夜上灯比例越来越高（以境外迁入为主），而元江以前半夜上灯为主，表现为持续北迁，北迁落点范围分布广；8-10月前后半夜上灯比例逐渐持平（既有本地迁出又有外地迁入），回迁虫源主要来自国内贵州、四川等地，本地虫源也向缅甸等境外区域迁出。【结论】 结果明确了云南南部草地贪夜蛾常年上灯行为节律、迁入迁出以及迁飞大气背景场，丰富了草地贪夜蛾周年繁殖区不同季节高空灯的灯下种群动态理论，进而为云南省乃至我国其他地区草地贪夜蛾迁入的早期监测预警与灾变预警提供依据。

[Objectives]  To investigate the migration of Spodoptera frugipeda in southern Yunnan and identify the source of migrating insects. [Methods]  An automatic searchlight trap was used to systematically monitor the movements and population dynamics of S. frugipeda in southern Yunnan in 2020. We inferred the source population based on trapping data, and by integrating meteorological data with insect flight trajectory simulation. [Results]  S. frugipeda moths were caught all year round, and there were multiple monthly peaks of abundance from March to April and June to October. The population dynamics of S. frugipeda in this region is complex, with populations comprised of varying proportions of local and migrating individuals in different seasons. From January to February, most moths were of local origin and are unable to migrate northward due to low temperatures. From March to April, captures consisted of a mix of locally bred and immigrant moths, with emigrating moths that reach Guizhou and Guangxi primarily originating from southeastern Myanmar. From May to July, a higher proportion of moths were captured in the latter half of the night in Jiangcheng, indicating immigration from outside China, whereas in Yuanjiang, most moths were captured in the first half of the night, indicating continuous northward migration. From August to October, the proportion of moths captured throughout the night stabilized, indicating a mixture of local and immigrant moths. Most immigrants came from locations within China such as Guizhou and Sichuan. Local moths are capable of migrating to other countries such as Myanmar. [Conclusion]  These results provide sights into the population dynamics and migratory behavior of S. frugipeda in southern Yunnan, and also elucidate the immigration, emigration, and atmospheric factors that influence the migration of this species. These findings contribute to our understanding of S. frugipeda population dynamics in different seasons, thereby providing information to improve the monitoring of S. frugipeda, including providing early warning of outbreaks, not only in Yunnan, but also in other parts of China.