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

• 1 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.
• 2 Cryptic and non-cryptic pupae were planted in pairs in the vegetation, and exposed to predators.
• 3 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.
• 4 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.
• 5 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.