Post industrialisation, soot covered trees are the reason behind

During post-industrialisation period, the tree trunks became dark due to industrial smoke and soot. It provided the advantage of camouflage to dark winged moths. Under this condition the white-winged moth did not survive due to predators, dark-winged or melanised moth survived. There was decrease in the population size of white winged moths. No variant is completely wiped out.