Wingspan 29 - 36mm. The male is blue above with a narrow black border and white fringe to the wings. The female can be very blue or very brown with no blue, or anywhere in between, with a border of orange marks on the fore-wings and black, white and orange marks on the hind wings. The under-wings are brown with orange, black and white markings along the borders and white circles with black centres across the wings. On the underside of the leading edge of the fore-wing there is a spot between the half-way spot and the body , which is absent in the very similar Brown Argus.
Grasslands with plenty of flowers, the caterpillars feed mainly on bird's-foot trefoil.
Status and distribution
Common and widespread across most of Britain, except the highlands. Common in Nottinghamshire and common at Netherfield Lagoons.
Best time to see
May to October, in two broods.