On the upper side the male is sulphur yellow and the female white with a greenish tinge but both have an orange spot in the centre of each wing. They never settle with their wings open and from the underside the sexes are more difficult to separate but the female is still paler.
Their wing shape is unique among British butterflies.
There is a popular myth that it is this butterfly which gave us the word BUTTERFLY, a corruption of butter-coloured fly.
