Field Guide
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Peppered Moth
Biston betularia
Not yet photographed by the community
Famous example of industrial melanism and natural selection.
Species Profile
Green List (common and widespread)
- Lifespan
- 2–4 weeks as an adult moth
- Size & Weight
- Wingspan 32–45 mm; 0.4–0.6 g
- Habitat
- Woodlands, parks, gardens, and urban areas with deciduous and coniferous trees, particularly birch.
- UK Distribution
- Widespread throughout England, Wales, and southern Scotland; absent from far northern regions. Resident year-round with peak activity June to August.
- Diet
- Adults do not feed; larvae feed exclusively on the leaves of trees, especially birch, but also alder, willow, and other deciduous species.
- Predators
- Birds such as thrushes and warblers; spiders; small mammals.
- Mating Season
- May to August, with peak activity in June and July
- Breeding
- Females lay 100–300 eggs singly or in small clusters on host plant leaves. Eggs hatch in 7–10 days. Larvae develop over 4–6 weeks through five instars; single generation per year, occasionally two in southern England.
- Behaviour
- Nocturnal and strongly attracted to artificial lights. Males are highly mobile and search for females using pheromone detection. Rests on tree bark during the day with wings folded tent-like over the body.
- •The Peppered Moth is famous for industrial melanism: during the Industrial Revolution, dark morphs became dominant in polluted areas due to predation pressure on pale forms against sooty bark.
- •The pale and dark colour morphs are controlled by a single dominant gene; the dark form (carbonaria) was extremely rare before 1850 but comprised up to 98% of Manchester's population by the 1890s.
- •Following Clean Air Act legislation in the 1970s, pale morphs have recovered in industrial regions, demonstrating rapid evolution in response to environmental change.
- •Adult moths do not feed and live on stored energy reserves accumulated during their larval stage.
- •The species' scientific name, betularia, refers to its association with birch trees (Betula species), though it uses many other host plants.
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