Genetic factors controlling flight performance and migration in the African armyworm moth,Spodoptera exempta(Walker) (Lepidoptera: Noctuidae)

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Abstract
The existence of a genetic component in the determination of flight capacity suggested by the results of previous experiments on the effects of environmental factors on flight performance inSpodoptera exempta(Walker) was confirmed by successful selection for and against the capacity for prolonged flight. The results of selection experiments were consistent with those expected when a polygenic character is subjected to directional selection. Heritability estimates for flight duration were 0·4 for overall heritability (mean offspring on mid parent regression) and 0·5–0·9 for single sex offspring on female and male parent regressions, demonstrating that flight capacity has a substantial additive genetic component. Although there can be no doubt that genetic factors play a major role in the control of migration inS. exempta, it is not yet clear whether flight capacity is a continuously varying character or whether discontinuous variation in the form of a genetically controlled flight polymorphism is involved. It is suggested that the life-history strategy ofS. exemptais adapted to maximise dispersal in the rains when a massive extension of favourable habitat occurs, and to maintain populations in those habitats which remain favourable in the dry season. The present evidence suggests that this strategy is achieved by cyclic selection of genetically determined variability in potential flight capacity.