Pupal colour polymorphism in Papilio machaon L. and the survival in the field of cryptic versus non‐cryptic pupae

SUMMARY A field experiment was carried out in a natural habitat of Papilio machaon L. in southern Sweden to assess the evolutionary significance of pupal colour polymorphism. Cryptic and non‐cryptic pupae were planted in pairs in the vegetation, and exposed to predators. The protective coloration conferred a selective advantage approximating 1.5 on the cryptic pupae of the summer generation. In the overwintering generation no difference could be detected between the predation of cryptic and non‐cryptic pupae. The adaptive fitness of protective coloration, as determined by the different rates of elimination of the colour morphs, was greater for the green pupae than for the brown ones. Natural selection favours the evolution of a seasonal difference in the proportion of green and brown pupae in the summer and hibernating generations of P.machaon.