Spot-distribution in Maniola jurtina (Lepidoptera) on small islands in southern Sweden

The Meadow Brown Butterfly, Maniola jurtina L., which is polymorphic for spotting on hind wings, was studied for five years on four small (0.15–1.0 km²) islands off the south coast of Sweden. Samples of females and males were unimodal for 0 and 2 spots, respectively. Spot-distributions remained unaltered in 1973–1974 but changed significantly in 1975 only to be restored again in 1976 and 1977. The change in 1975 was assumed to be associated with an unusually dry and warm summer and the results are discussed in terms of natural selection.