Scientists from the University of Exeter (United Kingdom) have shown that the spotted moth, also known as 'Darwin's moth' for having been identified as an evolutionary example, uses its color to better camouflage itself from the birds that feed on them, which caused them to darken when industrial pollution blackened British forests in the nineteenth century.

"It is one of the most emblematic examples of evolution, but fiercely attacked by creationists who seek to discredit the theory of evolution," says Martin Stevens, of the Center for Ecology and Conservation of the Penryn Campus of the University of Exeter. The study has been published in the journal Communications Biology.

The mottled moth or butterfly of the birches (Biston betularia) owes its name to this tree, whose trunk it uses to camouflage itself before the predators. In the 19th century, with the Industrial Revolution and the atmospheric pollution produced by the coal dust, the bark of the trees darkened, which also caused the moths to darken.

This phenomenon, called industrial melanism, in which the darker varieties prevail in contaminated areas, served to demonstrate Charles Darwin's theory of evolution by natural selection, being a subject of debate between evolutionary and creationist biologists. Afterwards, the disappearance of the coal dust pollution returned to harmonize the amount of lighter moths, which were majority before the Industrial Revolution.

The study by the University of Exeter has shown that moths manage to camouflage themselves in the trunks of trees effectively to the vision of predatory birds. "Using digital image analysis to simulate bird vision and field experiments in British forests, we compare the ease with which birds can see dark and pale butterflies, and determine their risk of predation," explains Professor Stevens.

"Our findings confirm the conventional history presented by the first evolutionary biologists: that the changes in the frequency of dark and pale butterflies were due to changes in pollution and camouflage," adds the Exeter researcher.