Phenotypic variation in adult morphology and pupal colour within and among families of the speckled wood butterfly Pararge aegeria

.1. Larvae from eggs of fifteen wild‐caught speckled wood females were reared individually under common conditions (LD 18:6 h and 17 °C) in the laboratory. 2. Pupal colour (green or brown) and the following adult morphological variables that are known or assumed to be related to behavioural variation (thermoregulation, flight, crypsis) were studied: size, relative thorax mass, area of yellow patches on the dorsal forewing, size of submarginal eyespots on the dorsal hindwing, colour of the dorsal thorax, dorsal basal wing, and dorsal distal wing. 3. The results of the breeding experiment indicate significant differences in adult morphological traits among families, sexes, and pupal colour types. 4. All adult morphological variables (except spot size and thorax colouration) differed significantly among families, suggesting genetic variation underlying the phenotypic variation. Heritabilities for these features were intermediate (0.38) to high (> 1). 5. Apart from known aspects (e.g. size), novel aspects of the sexual dimorphism were found: females had paler thoraxes than males, which relates to higher abundance of fur on the thorax and hence to thermoregulatory differences. 6. Green pupae produced larger individuals with a larger relative thorax mass than brown pupae. Green pupae produced adults with a paler basal wing colour in females, but not in males. These relationships are novel and suggest a trade‐off between juvenile and adult investment.