Figure 7.15 Selection by bird predation for different moth phenotypes. (a) In unpolluted forests, trees have light-colored bark and moths with the light phenotype are better camouflaged. (b) In polluted forests, trees have dark-colored bark and moths with the dark phenotype are better camouflaged. (c) When researchers placed both moth phenotypes on trees in polluted and unpolluted woods, fewer light-colored moths were consumed by birds on unpolluted trees but fewer dark moths were consumed on polluted trees.

Data from B. Kettlewell, Further selection experiments on industrial melanism in the Lepidoptera, Heredity 10 (1956): 287–301. Photos by Michael Willmer Forbes Tweedie/Photo Researchers, Inc.