Industrial melanism is an adaptation where the moths living in the industrial areas developed melanin pigments to match their body to the sootcovered surroundings. These melanic forms are mainly distributed in and around large industrial cities, where the environment has been altered by the pollution of the atmosphere; and is manifested by the appearance of dark colour of lichen-covered tree trunks, on which the moths rest during the day time. The peppered moth exists in two strains (forms) : light coloured (white) and melanic (black). In the past, bark of trees was covered by whitish lichens, so white moths escaped unnoticed from predatory birds. After industrialization barks got covered by smoke, so the white moths were selectively picked up by birds. But black moths escaped unnoticed so they managed to survive resulting in more population of black moths and less population of white moths.