The evolution of environmentally‐cued pupal colour in swallowtail butterflies: natural selection for pupation site and pupal colour

Abstract

1. Environmentally‐cued pupal colour in swallowtail butterflies has been hypothesized to evolve as a consequence of (a) the evolution of a preference for pupation sites above the ground that vary in colour and (b) natural selection for crypsis on such sites.2. This hypothesis was tested by comparing the field survival of green and brown Papilio polyxenes Fabr. pupae placed on green or brown pupation sites that were either above the ground on near the ground.3. Green pupae on green sites above the ground had a significantly higher probability of survival than did all other pupal colour and pupation site combinations.4. Pupae on sites above the ground were more likely to be preyed upon during the day, whereas those on sites near the ground were more likely to be preyed upon during the night, suggesting that variation in nocturnal and diurnal predation influences the evolution of pupation site preference.5. To the extent that diurnal predators use colour vision to locate prey, diurnal predation should favour environmentally‐cued pupal colour.