The peppered moth (Biston botularia) is an inconspicuous member of the family Geometridae, a night-flying species thought to spend its days resting camouflaged among the lichens that grow on tree trunks. The moth's predominant form has white wings, "peppered" with black specks or faint black lines, perfect for blending in with its tree bark environment. Less common is a variant, carbonaria, which is a black-winged moth, with increased levels of melanin (black pigment) causing the color change. The peppered moth has come to play a significant role in two important stories in science.

In 1859 British naturalist Charles Darwin proposed a theory of evolution in his book On the Origin of Species. He based his theory on three observations he made while collecting data on plants and animals during a five-year trip around the world in the survey ship Beagle: that living things vary, that they can...