The Brimstone butterfly is apparently the one that gave us the name 'Butterfly'. It was known to early scientists as the 'butter-coloured fly', which became 'Butterfly'. It is a fairly large butterfly, yellow all over, with a single darker yellow spot in the centre of each wing. The underside is paler, yellow to pale green, with veining and a single brown spot on each wing. It is found in open or rough ground, and visits gardens. It settles with its wings closed, and seems fond of Thistles.
The caterpillar is green, and larval foodplants are Buckthorn (Rhamnus catharticus) and Alder Buckthorn.
The females are a pale greenish-yellow, and with the veining and spots on their underside look very like a leaf.
