Melanism in the Peppered Moth Biston betularia (L.) in western Norway (Lepidoptera: Geometridae)

Abstract

Light-trap samples of the Peppered Moth Biston betularia (L.) from the region of Bergen, western Norway, show that about 85-95 % of the individuals are non-melanic (typica) and of the melanics, the form insularia predominates over carbonaria which was found in six samples but in low frequencies (2-5 %) except in one locality (9 %). The darkest individuals, classified as carbonaria, have some white speckling on the forewings like the ancient carbonaria in Great Britain a hundred years ago. There was no clear pattern regarding the geographic distribution of melanism; the frequency of insularia possibly being higher in coastal and more oceanic localities. There is no clear evidence of industrial melanism although the highest frequency of carbonaria was found near the source of a local industrial pollution.