Industrial melanism is widespread in the Lepidoptera (butterflies and moths), involving over 70 species such as "Odontopera bidentata" (scalloped hazel) and "Lymantria monacha" (dark arches), but the most studied is the evolution of the peppered moth, "Biston betularia". It is also seen in a beetle, "Adalia bipunctata" (two-spot ladybird), where camouflage is not involved as the insect has conspicuous warning coloration, and in the seasnake "Emydocephalus annulatus" where the melanism may help in excretion of trace elements through sloughing of the skin. The rapid decline of melanism that has accompanied the reduction of pollution, in effect a natural experiment, makes natural selection for camouflage "the only credible explanation".