Abstract
A profound change of color has occurred among hundreds of species of moths in industrial areas in different parts of the world. Less than a century ago moths of certain species were characterized by their light coloration, which matched such backgrounds as light tree trunks and lichen-covered rocks, on which the moths passed the daylight hours sitting motionless. Today in many areas the same species are predominantly dark. This reversal is called industrial melanism. An attempt has been made to analyze the phenomenon of industrial melanism. A survey is in progress of the present frequency of light and dark forms of each species of moth in Britain that exhibits industrial melanism. Each of the two forms are being examined to see if there are any differences in behavior, mating preferences and relative mortality. These experiments lead to the following conclusions. First, when the environment of a moth changes so that the moth cannot hide by day, the moth is eliminated by predators unless it mutates to a form that is better suited to its new environment. Second, once a mutation has occurred, natural selection alone can be responsible for its rapid spread. 5 figures, 1 table.
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