Common blue butterfly Polyommatus icarus

The common blue is a small blue butterfly which flies throughout the summer between April and October. The most widespread of the blue butterflies, it is found in a variety of habitats including heathland, woodland rides, grassy meadows, parks and even large gardens. Caterpillars feed on clovers, restharrow, bird’s-foot trefoil and related plants.


The male common blue has bright blue wings with a brown border and white fringe. The female is brown with a blue ‘dusting’ near the body. The common blue can be distinguished from the holly blue by the orange spots on the underside of the hind wings. It is larger than the small blue, brighter than the chalkhill blue and lacking the black- and white-chequered pattern along the edge of the wings of the adonis blue (the latter two are found on chalky grasslands in southern England). It is larger than the silver-studded blue, which is found on heathland, and smaller than the very rare large blue.


  • Wingspan: 2.9-3.6cm




Found right across the country, but absent from the Shetland Islands

When to see

April – October


  • The common blue was accidentally introduced to North America at a Canadian airfield in 2005, probably arriving on board a plane, and is now spreading in the area.
  • In southern parts of the UK common blues have two broods of young, usually in May and August, whereas in Scotland, they only have one brood that emerges in July

Common name

Common blue butterfly

Species name

Polyommatus icarus

IUCN Red List status

Least concern

When to see in Scotland

April – October

Where to see in Scotland

Scottish Wildlife Trust reserves such as Gailes Marsh or Linn Dean.

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