A Peppered Moth, Biston betularia, was drawn to my scientific moth trap last night. This species is probably the most important moth, scientifically speaking. It’s something of a Victorian scientific hero, in fact, and a speckly example of how evolution doesn’t always need millions of years to happen.
During the sooty days of the Mancunian branch of Britain’s Industrial Revolution, this creamy white moth with black peppery speckles evolved to an almost black form (Biston betularia betularia morpha carbonaria). Originally, it had been well camouflaged on lichen, but the lichen was killed off by the smoke and smog and the moth had to change rapidly to avoid detection by its avian predators. Indeed, the ones that evaded detection were the darker ones that evolved camouflage on the soot-encrusted buildings, posts, and trees of that era.
The rapid change from a bright to a dark, melanic form, industrial melanism as it is now known, provided evidence of survival of the fittest, natural selection, and evolution in action. By the end of the century, 95 per cent of the Peppered Moths in Great Britain were carbonaria.
The melanic form began to decline after the Clean Air Act of 1956. The specimen pictured below was drawn to actinic light last night and is obviously the original form of the moth, white, peppered with black specks. It’s also perhaps one of the more obvious names for a moth species.