Seasonal polyphenism in the wild: survey of wing patterns in five species of <i>Bicyclus</i> butterflies in Malawi

Abstract. For three successive years Bicyclus butterflies were caught on a daily basis at a field site in Malawi. Over 5000 butterflies, belonging to five species, were captured. Eight characters describing their plastic wing pattern were measured and analyzed. Broadly speaking, the plasticity is similar for all species, with the wet season forms having conspicuous wing markings (e.g. eyespots), and dry season forms lacking these markings. However, at a more detailed level, each species has its own specific form of plasticity with especially clear differences in the number of intermediate forms. Females generally show a higher degree of plasticity than males. The relative frequencies of intermediate forms and the difference between the sexes are associated with differences between the species in their preference for more open habitats or forests. The species with the most divergent plasticity is also ecologically and phylogenetically comparatively distant from the others.