Purple Hairstreak

Adventure step • Meet the species

Overview

The Purple Hairstreak is a fascinating small butterfly that lives in close symbiosis with oak trees. With a wingspan of just 2.6-3.4 centimeters, it belongs to the gossamer-winged butterfly family Lycaenidae, and its life is intimately connected to oaks. Males are particularly beautiful with metallic purple upper wing surfaces that shimmer in sunlight, while females have more subdued dark brown wings with only a faint purple sheen. The undersides of both sexes are grayish with white streaks and orange spots near the hind wing margin. This species has a very special life cycle that is completely dependent on oak trees. Females lay their eggs in the scales of oak buds, where the larvae overwinter before hatching in spring. The newly hatched caterpillars begin by eating oak buds and male flowers, but later develop a remarkable partnership with ants. The larvae secrete a sweet liquid that ants love, and in exchange, the ants protect the larvae from predators. This mutualistic relationship continues even when the larva transforms into a pupa among leaves and debris at the oak's base. The Purple Hairstreak is remarkably faithful to its tree and rarely leaves the oak canopy. The butterflies spend most of their lives high in the treetops where they bask, mate, and seek nourishment. Males are territorial and aggressively patrol their domain in the canopy, often sitting on exposed branches where they can survey their territory. They fly primarily during afternoons and early evenings when the sun warms the oak canopy. In Europe, the Purple Hairstreak occurs wherever mature oaks are found, from southern Scandinavia south through central and southern Europe to the Mediterranean, and east into Asia Minor. Despite being relatively common, it is often difficult to spot because it spends so much time high in the treetops. The species serves as an excellent indicator of valuable oak habitats and old-growth oak woodlands.