Peppered moth (Biston betularia) showing a comparison of the melanistic form f. carbonaria next to the typical paler form on dark soot-covered bark. The melanistic form has long been cited by genetic studies as an example of industural melanism. Sooty deposits on trees and other surfaces meant that the darker form was better camouflaged and more successful in industrial areas of Northern England. In recent decades air quality has improved to the extent that the melanistic form is declining in these areas and is now less frequently encountered than the typical form. Peak District National Park, Derbyshire, UK. July.