Oak Eggar

• The males fly in full sun, with an erratic and very fast flight, tracking the pheromone of the females, which by contrast are nocturnal and barely move.
• Its caterpillar, large and very hairy, can take two years to complete its development in mountain populations, overwintering twice.
• The caterpillar's hairs are irritant and cause a rash on contact.
• Its name misleads: despite being named after the oak, the caterpillar feeds mostly on heather and bramble, and heathland populations do not depend on oak at all.
• Sexual dimorphism is marked: the male is reddish brown and flies by day at great speed, seeking females by scent, while the female is larger, paler and flies at night.
• Watching the males patrol in zigzags over the heather moors in broad daylight is a characteristic scene of the European summer, and it puzzles anyone who expects a moth to be nocturnal.
• In the north of its range the cycle takes two years: the caterpillar overwinters twice before pupating.
• The caterpillar is large and very hairy, with hairs that can cause irritation.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat & environment

Heathland, scrub, moorland and woodland edges of Europe

Sources consulted: Butterfly Conservation (Reino Unido); Lepiforum; Speybroeck et al.

Best time: July to September, with the males flying by day in full sun