Common (bottom right) and melanistic (top left) peppered moths rest on a tree trunk blackened with coal soot

Common (bottom right) and melanistic (top left) peppered moths rest on a tree trunk blackened with coal soot. Wikimedia Commons.

Common (lower right) and melanistic (top left) peppered moths rest on an unpolluted tree trunk Dining hall of Exeter College, Oxford, 1908, covered in soot.