Biston betularia

The most useful field mark is the moth's "peppered" wing pattern: white wings speckled with black spots and crossed by black lines of varying distinctness. The wingspan ranges from 45 to 62 mm, with a median around 55 mm.

The body is relatively stout, while the forewings are narrow and elongate by comparison. The amount of black speckling varies considerably between individuals, from wings that are nearly clear of spotting to ones so densely marked they appear black sprinkled with white.

In rare instances, the speckling and cross-lines can appear grey or brown instead of black, and occasionally as a mixed brown and black/grey pattern. Males can be distinguished by their strongly bipectinate (feather-like) antennae, which they use to detect female pheromones.

The peppered moth occurs across a wide range of the northern hemisphere, including much of China (from Heilongjiang and Inner Mongolia to Sichuan, Yunnan, and Tibet), Russia, Mongolia, Japan, North and South Korea, Nepal, Kazakhstan, Kyrgyzstan, Turkmenistan, Georgia, Azerbaijan, Armenia, Europe, and North America.

It is widespread in deciduous and mixedwood forests, parklands, and shrublands, and also turns up in woodland, hedgerows, parks, and gardens, including urban settings.

Observation records through the year show a sharp rise heading into summer, suggesting the adult flight period is concentrated in the warmer months, though these presence records do not reflect overall population size or the moth's complete range.

By day, the peppered moth hides from predators, particularly birds, choosing resting positions that make the most of its camouflage. It favors three main types of site: just below a branch-trunk joint on a tree trunk where it sits in shadow, the underside of branches, or on foliate twigs.

Studies watching where moths naturally settle found that in Cambridge, over half of 135 moths examined rested on tree branches, mostly on the lower half, 37% sat on tree trunks (mostly on the north side), and only about 12.6% rested on or under twigs.

Camouflage effectiveness depends on the background: the lighter-patterned form blends well against crustose lichens both to human eyes and in ultraviolet wavelengths, which birds can see, but is less well hidden against foliose lichens on tree trunks, since those lichens do not reflect ultraviolet light the way the moth's wings do.

When mating, a pair will spend the day hidden together, with the male staying close to the female to ensure paternity before moving on.

As larvae, peppered moth caterpillars feed on the foliage of a wide range of trees and shrubs, including beech (Fagus sylvatica), English oak (Quercus robur), goat willow (Salix caprea), and common alder (Alnus glutinosa).

They also take from birches, including silver birch (Betula pendula) and downy birch (Betula pubescens), as well as shrubby and herbaceous plants such as mugwort (Artemisia vulgaris), butterfly-bush (Buddleja davidii), hawthorn (Crataegus monogyna), and broom (Cytisus scoparius).

This broad range of recorded food plants, spanning trees, shrubs and herbs, points to a caterpillar that is not tied to a single host but can develop on whatever suitable deciduous foliage is available in its woodland, hedgerow or garden habitat.

1. Charles Darwin helped found the Entomological Society of London in 1833, yet he never wrote specifically about the peppered moth despite its later fame in evolutionary biology.
2. In folklore and symbolism, black moths in general are often associated with sensuality, fragility, seduction, darkness, and death, and in many cultures they carry mysterious or magical associations.