Clouded Yellow (Colias Croceus)

Clouded Yellow

(Colias Croceus)

Normally, fewer than 500 Clouded Yellow butterflies are seen in Britain each year. The species is a regular migrant to Great Britain, usually arriving in late May. It is a strong, fast flyer which comes from Southern Europe. In its warm native countries it is a prolific breeder, producing up to four broods a year. Females each lay up to 600 eggs on Clover, Lucerne, Trefoils and Melilot.

Occasionally there is a big influx into Great Britain after the European population has swollen in favourable conditions. In 1947 an estimated 36,000 butterflies came; 1955 and 1983 were also 'Clouded Yellow years'. Spring migrants to Britain lay eggs that give rise to a single brood of Autumn butterflies and in recent years some have managed to survive well into December and even overwinter as chrysalis in the South of England.

The butterflies spend most of their time feeding on the nectar of wild flowers such as Lucerne, Clover, Thistle, Knapweed and Marjoram. Aubrietia and Marigolds may attract them to gardens. They flit swiftly from flower to flower, are easily disturbed and are hard to approach. Always poised for flight, they never rest with wings open. The females' colouring is variable; some have few or no spots in the black margin and there is a form called helice which has a whitish background.