Bernard Kettlewell, a British field biologist, was convinced that wing coloration is an important adaptation in peppered moths (Biston bestularia). These moths rest on trees with their wings spread open in order to camouflage. This is thought to provide some protection against predatory birds. Kettlewell suspected light-colored wings provided camouflage when moths rested on lichens that grow on the surface of tree trunks in British forests. The camouflage is so effective that the moths are invisible to humans standing only a few feet away.
As a result of the Industrial Revolution, many areas of Britain became heavily polluted, causing the lichens to die off and the trees to darken with soot from burning coal. Here, the adaptive value of wing coloration was reversed. Against a dark background, darker moths (the dominant trait) are camouflaged and light-colored moths are more conspicuous (visible).
