Dark moths would have an advantage when their dark color helps them hide better from predators in a darkened environment, especially on soot‑darkened tree bark during industrial pollution.

Core idea

When the environment becomes darker (for example, because of soot from factories during the Industrial Revolution), dark-colored moths blend in with the background more effectively than light-colored moths. Predators like birds have a harder time seeing and catching these camouflaged dark moths, so more of them survive and reproduce.

Camouflage and predation

  • Dark moths on dark, polluted tree trunks are less visible to birds, so they are less likely to be eaten.
  • Light moths stand out against the same dark background, making them easier for predators to spot and catch.

Natural selection in action

Over many generations, this survival difference gives dark moths a selective advantage in polluted areas. Because more dark moths survive to reproduce, genes for dark coloration become more common in the population in those environments.

When the environment changes back

When pollution is reduced and tree bark becomes lighter again (for example, as lichens return), the advantage switches. In cleaner woodlands, pale moths are better camouflaged, so they survive and reproduce more than dark moths, and their frequency increases instead.

Bottom line: dark moths have an advantage only when their coloration matches a dark environment, because camouflage reduces predation and boosts their chances of survival and reproduction.