New evidence on the migration of moths of the African armyworm, Spodoptera exempta (Wlk.) (Lepidoptera, Noctuidae)

Abstract

Fresh evidence is described which supports the theory that moths of the Noctuid Spodoptera exempta (Wlk.) (the adult stage of the African armyworm) are migratory. The evidence comes from four main sources: a study of fluctuations in numbers of moths caught in a network of light-traps operated in East Africa; the fertilisation rates in samples of females as shown by dissection; the sex ratios in samples of moths caught in light-traps; and a study of the behaviour of moths in the field during the period immediately following emergence. In certain of these features S. exempta is compared and contrasted with the related S. triturata (Wlk.), in which the evidence points against extensive migration.It is concluded that migration occurs in S. exempta, probably on an extensive scale, and that it therefore has an important bearing on the occurrence and distribution of outbreaks of the larvae.