The answer is industrial melanism.
During the Industrial revolution, due to pollution, trees
become darker in the urban area. Light-colored moths were, thus, easy prey. The
dark-colored moths were able to camouflage on dark trees and avoid predators.
The phenomenon is known as industrial melanism. So, in polluted urban areas,
the number of dark-colored peppered moths increased. In the clean environment,
were much effective in hiding from predators and they outnumbered the
dark-colored moths.
