Belongs to: blues and hairstreaks
Compare with: brown argus
holly blue
Common blue Polyommatus icarus
Best time to see: Jun to mid Sep
Key facts
Our commonest and most widely distributed blue butterfly
Habitat: sunny, grassy places – meadows, road verges and short grassland
Common throughout the British Isles except in highland areas
Recognition
Male is bright blue above with a black-and-white margin; female dark brown with orange crescents and dark spots
Both have pale brown underwing with black spots and orange marks around the margin
Flit just above ground by day and roost communally at night in sheltered clumps of tall grass; wingspan 35 mm
Lifecycle
Eggs are small white discs laid on birdsfoot trefoil plants in June and again in August
Caterpillars are plain green and slightly furry, hibernating among dead leaves when quite small
The chrysalis forms on the ground and is buried by ants; adults emerge in May/June and again in August
© David Corke
© Iris Newbery