ADAPTIVE SIGNIFICANCE OF PIGMENT POLYMORPHISMS IN COLIAS BUTTERFLIES, II. THERMOREGULATION AND PHOTOPERIODICALLY CONTROLLED MELANIN VARIATION IN <i>Colias eurytheme</i>

Abstract

The butterfly Colias eurytheme requires body temperatures above 30 degrees C for flight. When cold, it orients its exposed wing undersides to present maximum surface area to sunlight; when too warm, it orients for minimum exposure. Dark-winged color forms heat faster in sunlight than light ones. The seasonal color polymorphism of Colias appears to have been evolved to maximize solar heating in cold seasons and minimize overheating in warm seasons.