Variation in the wingspot size and asymmetry of Banded Demoiselle Calopteryx splendens (Harris, 1792)

Wing pigmentation of calopterygid damselflies has received considerable attention due to its role as an honest signal of male quality. We describe a quantitative analysis of this trait in two populations of the Banded Demoiselle, Calopteryx splendens (Harris 1780) in England. One population, sampled close to the northern limit of its range in Northumberland, exhibited substantially smaller wing spots than in a population sampled in Hampshire. Wing asymmetry (in terms of length and area) did not vary between the two populations, nor did it co-vary with the size of the wing spots. We propose that the decline in wing spot size is the result of variation in climate between the two sites. Such variation in immunocompetence could contribute to the determination of range margins in this species.