Best time to see: early Jul to late Aug

Key facts

A large woodland butterfly, with wings that refract the light and turn brilliant purple in the sun

Habitat: extensive wooded areas with open ground containing small groups of trees

Its distribution had shrunk to central southern England but now it is spreading again, including into Essex

Recognition

Upperwings dusky, underwings greyish-brown, both with a white band and white spots; wingspan around 8cm

Males congregate around tall trees, making soaring flights and battling with one another

Males descend sometimes to drink sap or puddles, but feed mainly on aphid honeydew; females seldom seen

Lifecycle

Eggs are laid singly on partly shaded leaves of sallows (aka pussy willow) in August

Grey-brown caterpillars with two horns feed on leaves and hibernate over winter on a silk pad

Pale silver-green chrysalis emerges in early summer