The Peppered Moth, Biston betularia, is one of the most important moths of the 20th century.
In the 1950s, Bernard Kettlewell wanted to explore why the Peppered Moth had evolved from its traditional peppered form to a much darker morph. The change had occurred since the industrial revolution and Kettlewell’s experiments sought to demonstrate that the moth had evolved to adapt to its changed environment. The soot emitted by factories in the industrializing country was coating the moth’s habitat so that its white ground form made it much more obvious to predators. Evolving to a dark or black form allowed the moth to become camouflaged once again. This was industrial melanism. The Kettlewell experiment is described in Wikipedia and it is well worth clicking through. I think I have read books in the past that challenge the integrity of Kettlewell’s methods but of course the moth has now reverted to its original form as the pollutants have been progressively removed from the atmosphere. So whatever the possible flaws in the methodology, Kettlewell’s experiments appear to stand up. This is evolution in action roughly within my lifetime. So if you see one of these, just reflect for a moment on how important it was back in the 1950s. I photographed it on a lichen-covered brick in our terrace simply to illustrate how well it blends in.