The fall armyworm (FAW), Spodoptera frugiperda, a major agricultural insect pest in the Western Hemisphere, currently also poses a significant threat to many cereal crops in Africa. FAW consists of two morphocryptic strains, the corn- and the rice strains, which were thought to display typical genetic, physiological and behavioural features. However, this is not absolutely true, rendering direct identification and distribution of the strains impossible in field. Thus, to investigate 1) the composition and diversity of FAW strains, 2) their distribution at various spatial scales, and 3) the host plants they use, in invaded countries we used the COI barcode fragment, a marker capable of accurately distinguishing the two strains. A total of 125 specimens mainly sampled on maize in Niger and Senegal and to a lesser extent in Guinea, Mali, Togo, Burkina Faso and Cape Verde were analyzed. Sixteen haplotypes were identified among which two occurred very frequently. Phylogenetic analysis delineated two lineages, the rice and corn strains, but no typical geographical and host-plant patterns were found. The FAW-strain haplotypes derived from West African specimens were genetically comparable with those sampled elsewhere in Africa, the Americas and Asia. Considering all sites and plants sampled, the corn strain slightly predominated but on maize, the two strains were statistically comparable. Their distribution is largely sympatric at region, field and even maize plant scales. These findings are compared to populations recorded elsewhere and are discussed in the framework of biological invasions, and the management and ecology of the species.

秋夜蛾（Spreadoptera frugiperda）是西半球的一种主要农业害虫，目前对非洲的许多谷物作物也构成了重大威胁。一汽由两个形态隐育菌株组成，即玉米和水稻菌株，被认为具有典型的遗传，生理和行为特征。但是，这不是绝对正确的，因此无法在野外直接鉴定和分布菌株。因此，要研究1）一汽一氧化碳菌株的组成和多样性，2）它们在各种空间尺度上的分布，以及3）他们使用的寄主植物，在被入侵的国家/地区，我们使用了COI条码片段，该标记能够准确地区分这两种菌株。总共分析了125个样本，主要在尼日尔和塞内加尔的玉米上进行了采样，而在几内亚，马里，多哥，布基纳法索和佛得角则进行了较少程度的采样。确定了16个单倍型，其中两个非常频繁。系统发育分析描绘了两个系，水稻和玉米品系，但没有发现典型的地理和寄主植物模式。源自西非标本的一汽单倍型在基因上与非洲，美洲和亚洲其他地方的样本具有可比性。考虑到采样的所有地点和植物，玉米菌株略占优势，但在玉米上，这两个菌株在统计学上具有可比性。它们的分布主要是在区域，田地甚至玉米的工厂规模上。将这些发现与其他地方记录的种群进行比较，并在生物入侵，物种管理和生态学的框架内进行讨论。