Peppered moth

The peppered moth, Biston betularia, is a widespread Eurasian moth with light and dark forms. Their changing frequencies during industrial pollution became a classic example of natural selection.

Industrial melanism: An increase in dark pigmentation in populations exposed to industrial environments. The moth’s changing color-form frequencies are a classic case of this broader pattern.
Biston betularia f. carbonaria: The dark form of the peppered moth, associated with a dominant allele for heavy pigmentation. Its rise in polluted regions made the color shift visible in population records.
Industrial Revolution: A period of major economic and technological transformation beginning in Britain in the late eighteenth century. Coal-burning industries created the soot pollution associated with the moth’s dark form increasing.
Mutationism: The view that large mutations, rather than gradual selection on variation, drive major evolutionary change. Heslop Harrison’s proposed direct induction of dark forms echoed this rival account of the moth’s change.
Natural selection: Evolutionary change in which heritable traits affect survival or reproduction and become more or less common. Differential survival of the moth’s color forms illustrates selection in a changing environment.
Biston betularia f. typica: The pale, speckled form of the peppered moth, usually patterned to resemble lichen-covered bark. Its decline in soot-darkened areas contrasted with the dark form’s rise.
James William Tutt: A British entomologist who proposed in 1896 that bird predation could explain the peppered moth’s changing forms. He supplied an early natural-selection explanation decades before Kettlewell’s experiments.
Lamarckism: The theory that traits acquired during an organism’s lifetime can be inherited by its descendants. The claim that pollution directly caused heritable darkening was sometimes mistaken for selection.
Camouflage: Coloration or structure that reduces an organism’s visibility against its surroundings. Moth coloration affected how well individuals blended with tree trunks where predators hunted.
Bernard Kettlewell: A British geneticist and ecologist who conducted influential experiments on peppered moth predation in the 1950s. His mark-release-recapture studies tested whether birds selected moths by visibility.

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