156563 Chalkhill Blue Polyommatus coridon Wingspan 40mm. Iconic downland butterfly, males of which are a unique colour amongst British blues. Adult male has pale sky-blue upperwings; female’s are dark brown with orange submarginal spots. Underwings of both sexes are grey-brown with spots. Flies July–August. Larva feeds on Horseshoe Vetch; sometimes discovered at dusk being attended by ants. Very local and restricted to chalk and limestone grassland in southern England.