Abstract: 【Aim】 This study aims to explore and understand the ovary developmental status of Spodoptera frugiperda and its variation in fields so as to provide accurate monitoring basis for the occurrence and migration dynamics of S. frugiperda populations. 【Methods】 The morphological differences of female ovary of S. frugiperda at different ages (day-old) and from fields of different regions in China were compared by systematic dissection of female reproductive system. The relationship between ovarian maturation and mating of female moths was analyzed. 【Results】 The reproductive system of female moth of S. frugiperda is composed of ovaries, oviducts, copulatory pouch, afferent duct, spermatheca, accessory glands and ovipositors. According to the morphological characteristics, eggs of field female moths can be divided into three stages: pre-vitellogenesis, vitellogenesis and maturation. The eggs in the ovaries of 1-day old female moths barely reach the middle stage of vitellogenesis with the ovarian stalk empty. The ovaries start to differentiate at the 3-day old female moth stage. Some ovaries in the 3-day old female moths are still similar to those in the 1-day old moths, but some ovaries have mature eggs. The differentiation of ovary lasts till the 11-day old female moth stage. Some female moths from fields of Jiangcheng County and Mile County of Yunnan Province, Tianyang County of Guangxi Province, and Rui′an County and Zhenhai County of Zhejiang Province had immature ovaries until death, which accounted for 61.5%, 51.7%, 41.7%, 42.1% and 35.5% of the total ovaries, respectively. A proportion of 39.6% of the first generation female moths reared indoors still had immature ovaries at the time of death, which was similar to that of the field female moths. The ovaries of mated female moths could be mature and immature, but the proportion of immature ovaries was only 18.0%±5.0%. 【Conclusion】 The results suggest that field female moths of S. frugiperda have a mixture of migratory and non-migrating individuals in the same generation, and their proportions vary with the location and season. The results of this study explain to some extent the uncertainty of occurrence and damage of S. frugiperda populations and provide a basis for monitoring the migratory status and green control of S. frugiperda in the field.

Key words: Spodoptera frugiperda, natural population, ovary, morphology, development, migration