The first brimstone butterflies are flying along woodland rides and sweeping across gardens. The males are very noticeable with their large, sulphur-yellow wings and their determined style of flight. Each of their wings also has a small orange-red spot on it. The females are a paler yellow, sometimes almost white. They have been hibernating in holly bushes and thick ivy on trees and walls. Their angled wings with pronounced veins look very like leaves, and provide good camouflage for them. They are tough butterflies, and once they are out and about in March, they can easily survive cold spells. They nectar on such early flowers as ground ivy, which is a small, aromatic, purple flower, and the contrast of colours looks very beautiful. Their caterpillars eat the leaves of two rather unfamiliar trees, buckthorn and alder buckthorn, and it might seem surprising that there are enough of these to sustain such a large and widespread population of brimstones. But they are rather dull, unnoticeable trees, with small leaves, and there are more of them about than one might think. A few red admiral and peacock butterflies have also emerged from hibernation.