A small, widespread butterfly. The male has blue wings with black-brown border and thin white fringe. The female is brown, similar to a Brown Argus, but with blue dusting near the body, like the female Adonis and Chalk hill Blues, which have dark veins in white fringes of wing margins. The brightly coloured males are conspicuous but females are more secretive. The colour of the upperwings of females varies from almost completely brown in southern England to predominantly blue in western Ireland and Scotland, but the colour is variable within local populations with some striking examples.
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The common blue is one of the most widespread butterflies in the UK, found throughout the U.K. including Orkney and the Western Isles (and occasionally Shetland), and on many of the smaller islands. It survives at altitudes up to about 500m, and can be found in a variety of habitats where its main larval food plant, bird€™s-foot trefoil (Lotus corniculatus) occurs. Sadly the common blue is no longer 'common'€ in many parts of the UK. The loss of wild flower grasslands through agricultural improvement has led to vast declines. Recent research has indicated that in some rural areas, the number of colonies may have declined by more than 75% over the last 50 years.
It occurs in a range of grassy places where its food plants grow in sunny, sheltered situations on downland, coastal dunes and undercliffs, road verges, acid grassland, and woodland clearings. It is also found in waste ground, disused pits and quarries, golf courses, and urban habitats such as cemeteries
Common Bird's-foot-trefoil (Lotus corniculatus) is the main food plant. Other plants used include: Greater Bird's-foot-trefoil (L. pedunculatus), Black Medick (Medicago lupulina), Common Restharrow (Ononis repens), White Clover (Trifolium repens), and Lesser Trefoil (T. dubium).
UK BAP status: not listed Butterfly Conservation priority: low European threat status: not threatened