The peppered moth, Biston betularia, is a common moth present in gardens, parks, hedgerows and woodland. They have pale-coloured wings with black markings; however, in the mid-1800’s, English naturalist R.S.Edleston discovered a dark-coloured peppered moth in the centre of Manchester – a colouration that became more common around cities as more coal-burning factories were built.
The cause of this colour variation was later recognised as being a mutation, a change in the DNA of the moth which was passed through the eggs to the next generation. The great advantage for the dark moths around industrial areas was that they were less likely to be noticed, and eaten by birds, when resting on sooty tree trunks and the like. In 1896, J.W.Tutt, an English schoolmaster and amateur entomologist, suggested that peppered moths were an example of natural selection.
An in-depth study in the 1950’s found that birds were twice as likely to eat a light-coloured moth on a dark tree than a dark variety. Dark moths therefore lived longer in dark woodlands and so had longer to breed.
