Peppered Moths: Melanism in Biston Betularia

Beginning in the late eighteenth century profound changes began to take place in the realms of manufacturing, agriculture and transportation in Britain. This period of change, known as the industrial revolution, had major impacts on both the socioeconomic and cultural conditions of the Western world. New discoveries were being made from all corners of the globe and things were progressing at a faster rate than ever before. All this progress did not come without a cost.

A major driving force behind this advancement was King Coal. To power industry, huge amounts of coal were burned. Some estimates show figures as high as 50 tons of industrial fallout per year in some industrial areas (Hooper). This fallout settled on trees in the form of soot, turning wooded areas in industrial centers black. Not to be outdone, many different wildlife species began to be noted as having dark forms. The rise of melanic forms had been seen in ladybird beetles, some spiders, some birds and many moth species (Wells). Of this last group, the most famous and the moth I'm going to focus this essay on, is Biston betularia. This essay will discuss the history of industrial melanism in B. betularia, the theories leading up to Henry Bernard Davis Kettlewell, Kettlewell's experiments, the work done post-Kettlewell, the fraud allegations surrounding his results and the overall implications this has on the teaching of biology and the theory of evolution, respectively.

There are three forms of Biston betularia, or the peppered moth. The pale form, typica, was the form that had been known initially. In the mid 18^th century a lepidopterist named Moses Harris first described the melanic version of the peppered moth which would later come to be known asform carbonaria (Harris 1776, Cook 2003). The third form of this moth is form insularia, which is an intermediate between the pale and dark forms ranging from pale mottled with dark scales to dark mottled with pale scales.