Maculinea arion in Scandinavia. a) Count data of M. arion imagos on Møn, Denmark. Maximum (solid line) and minimum (dashed line) counts from the best day during the flight season. Imago counts were converted into approximate population census size (# imagos × 3.5) according to Thomas et al. . b) Distribution of M. arion in Denmark and southern Sweden before (open symbols) and after (closed symbols) 1990, 10 km2 UTM grid. Records have been compiled since 1900 by the Atlas Project of Danish Butterflies and the Swedish ArtDatabankens fynddatabas. Danish populations marked by an asterisk went extinct in the late 1990s.