Scientific name: Colias croceus
This migrant butterfly always rests with its wings closed, showing its greenish-yellow underwings with two distinctive silver-white spots. The upperwings are deep orange-yellow, with broad dark wing margins (the female's wing margins are darker than the male's).
The Clouded Yellow is one of the truly migratory European butterflies and a regular visitor to Britain and Ireland. Although some of these golden-yellow butterflies are seen every year, the species is famous for occasional mass immigrations and subsequent breeding, which are fondly and long remembered as ''Clouded Yellow Years''. A small proportion of females are pale yellow (the form helice), which can be confused with the rarer Pale and Berger's Clouded Yellows.
The bottle-shaped egg is laid singly on the upperside of legume leaves (e.g. Clover or Lucerne) in mid-June and within a couple of days turns from a pale yellow to pink, then orange. It hatches in around seven days.
The caterpillar is a well-camouflaged green with a yellow stripe along each side of its body once it is fully grown. It moults five times over a period of three to six weeks, depending on the temperature.
The chrysalis is well hidden from predators, attached to the stem of its foodplant with a silken girdle. This stage of its lifecycle lasts between two to three weeks.
Size and Family
- Family: Whites and yellows
- Size: Large
- Wing Span Range (male to female): 57-62mm
The caterpillar feeds from a range of leguminous plants, including wild and cultivated clovers (Trifolium spp.), Lucerne (Medicago sativa), and less frequently, Common Bird's-foot-trefoil (Lotus corniculatus).
Clouded Yellows may be seen in any habitat, but congregate in flowery places where the larval foodplants grow. As clovers are still commonly cultivated, the Clouded Yellow is one of the few butterfly species that has no difficulty locating breeding habitat in the modern farmed countryside. In southern England it has a preference for unimproved chalk downland.
- Countries: England, Ireland, Scotland and Wales
- Anywhere, but most commonly close to the coast in southern England.
- Distribution Trend Since 1970’s = +144%.