In Iceland the carabid beetle Amara quenseli (Schönherr) is polymorphic for wing length and frequencies of macropterous, brachypterous, and intermediate individuals were scored in different habitats. Macroptery and brachyptery varied geographically between < 1-28 % and 14-43 %, respectively. Long-winged individuals are assumed to represent a flying morph, and the frequency is related to the relative age and stability of the habitats. Females tend to show a higher degree of macroptery (and a seasonal decline) than males, which is thought to reflect differences in activity patterns of the sexes. The wing polymorphism is adaptive in response to the environmental conditions, rather than indicating the age of the population.