Small yet stunning, the purple hairstreak is rarely seen as it spends much of its time fluttering high up in the tree canopy. Reliant on oak woodland, this little butterfly is never far from oak trees.
Common name: purple hairstreak
Scientific name: Favonius quercus
Family: Lycaenidae
Habitat: oak woods
Caterpillar foodplants: sessile and English oak, and occasionally non-native oaks
Predators: birds
Origin: native
Caterpillars: brown and chunky with a deeper brown line along its back and paler oblique line along each side. It is covered in hairs and camouflages itself well against brown tree buds.
Adults: males are completely purple above while females only have a purple marking on the forewing. The underside is silvery grey with an orange eyespot on the hindwing. Both sexes have a pale streak under their wings, and they usually have short tails on the ends of their wings which resemble antennae.
Wingspan: 3-4cm
Caterpillars: the leaves and flower buds of English oak and sessile oak.
Adults: mainly honeydew (a sweet substance secreted by aphids feeding on tree leaves), but sometimes also nectar sources like bramble.
Caterpillars rest during the day, waking at night in order to feed.
Credit: Papillo / Alamy Stock Photo
Towards the end of summer, eggs which look like miniature sea urchins are laid at the base of plump oak buds. While the caterpillars develop within the egg quickly, they remain dormant over the winter. They hatch the following spring when the buds break, with the caterpillars burrowing into the flower buds to feed. They reach adulthood by July.
The purple hairstreak relies entirely on the oak tree to survive, using it as a food source, home and place to lay eggs. It is mostly found in oak woods across southern England and Wales, with scattered colonies further north. Recently it has been extending its range, particularly in the midlands, south-west Scotland and urban areas like London.
Credit: Andy Sands / naturepl.com
Step out into your nearest oak wood on a warm July evening, and look skyward. They can be difficult to spot, but if you’re lucky, purple hairstreaks will be out to play. They tend to stay around the treetops, and love nothing more than a game of chase on a summer’s evening – whole colonies can hang out in a single oak.
The purple hairstreak is common and not threatened in the UK at present.
