- Lifespan
- 13–14 months; one of the longest-lived British butterflies, overwintering as adults
- Size & Weight
- Wingspan 50–56 mm
- Habitat
- Woodland edges, hedgerows, parks and gardens with buckthorn and alder buckthorn shrubs.
- UK Distribution
- Found throughout England, Wales and southern Scotland; resident year-round, with populations reinforced by continental immigrants in autumn.
- Diet
- Adults feed on nectar from early spring flowers, rotting fruit, and tree sap; caterpillars feed exclusively on buckthorn (Rhamnus cathartica) and alder buckthorn (Frangula alnus).
- Predators
- Birds, particularly robins and thrushes; spiders and small reptiles also take adults and larvae.
- Mating Season
- July to September, with mating resuming briefly in spring before egg-laying
- Breeding
- Single brood per year; eggs laid singly on buckthorn leaves in late spring; caterpillars develop through summer; pupation occurs in late summer with adults emerging in autumn.
- Behaviour
- Brimstones are solitary and territorial; males patrol in sunshine seeking females. They overwinter as adults in ivy, evergreens or hollow trees, emerging on mild winter days. The species is one of the earliest butterflies to appear in spring.