  Although all of the illustrations of the epistemology of experiment come from physics, David Rudge (1998; 2001) has shown that they are also used in biology. His example is Kettlewell’s (1955; 1956; 1958) evolutionary biology experiments on the Peppered Moth, Biston betularia. The typical form of the moth has a pale speckled appearance and there are two darker forms, f. carbonaria, which is nearly black, and f. insularia, which is intermediate in color. The typical form of the moth was most prevalent in the British Isles and Europe until the middle of the nineteenth century. At that time things began to change. Increasing industrial pollution had both darkened the surfaces of trees and rocks and had also killed the lichen cover of the forests downwind of pollution sources. Coincident with these changes, naturalists had found that rare, darker forms of several moth species, in particular the Peppered Moth, had become common in areas downwind of pollution sources.