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 (form helice), which can be confused with the rarer Pale and Berger's Clouded Yellows.
The Clouded Yellow is a true migrant. Breeding grounds are found in North Africa, extending into Southern Europe. During summer the migrants are found all across the British isles and Europe. The butterfly is also found in Asia ranging from Siberia to India.
The Clouded Yellow is a strong migrant, and most years it reaches southern England, occasionally travelling into Wales, Ireland, northern England and southern Scotland. Some years these colourful butterflies are abundant in southern Britain and in other years only a few make it this far north. The origin of these migrants is northern Africa and southern Europe, where they are both widespread and abundant except at very high altitudes.
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 have no difficulty locating breeding habitat in the modern farmed countryside. In southern England, there is a preference for unimproved chalk downland.
