The effect of wing colour on male behavioural strategies in the speckled wood butterfly

The behaviour of male speckled wood butterflies,Pararge aegeriaL. (Satyrinae), was studied in relation to the following phenotypic traits: dorsal wing colour, submarginal wing spots, wing length and generation. Wing colour was of overriding importance. Pale males spent most of their time resting within a sunlit patch and engaged in short flights and intra- and interspecific interactions. Darker males flew more frequently between sunlit patches through the shaded forest. Thus males differing in phenotype did not have the same probability of showing perching, patrolling or an intermediate type of mate-locating behaviour. Darker and larger males were also more likely to leave the forest. There was very little effect of spot type, but a clear influence of generation on the behavioural variation. It is hypothesized that the observed variation is related to differences in thermoregulation between differently coloured individuals. Darker individuals are expected to have an increased warming rate which means that they can spend more time flying through the shady wood from one sunlit patch to another, while pale males will not suffer from overheating as soon as dark ones when settled on a sunlit patch. This in turn causes variation in their adaptedness to different behavioural strategies.