Abstract
MELANISM has long been a subject of special interest to British entomologists owing to the rise and spread of melanic varieties in many British species of moths and butterflies, such groups as the Geometridæ showing many examples. Records of melanism go back at least to 1850, when the dark variety Doubledayaria of Amphidasys betularia appeared near Manchester. It afterwards spread until it became the prevalent or exclusive form in Lancashire and the Midland Counties, extending also to the Continent in later years. The earlier naturalists' point of view (as represented by the writings of Tutt and of Porritt) concerning its causation, related it to the progressive darkening of the background in the neighbourhood of cities as a result of industrialisation. When this explanation was found to be inadequate, moisture was added as a cause of melanism; and Tutt concluded that moisture would darken the surfaces of rocks in rural districts just as smoke darkens surfaces in urban areas, natural selection progressively favouring darker forms which habitually rested on such darkened backgrounds.
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Melanism in British Lepidoptera. Nature 105, 278 (1920). https://doi.org/10.1038/105278a0
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DOI: https://doi.org/10.1038/105278a0