Dark forms of the British peppered moth (Biston betularia), as well as many other species of moth, became common in the middle of the 19th century near centres of industrial pollution. Soot coated the trunks and branches of trees, and killed lichens.  In the photos, a pale form (typica) and a dark form (carbonaria) rest side-by-side on an unpolluted lichen covered trunk in Dorset (above), and a soot-covered trunk near Birmingham.  (From HBD Kettlewell, 1956, Heredity 10: 300).