The Clouded Yellow is one of the truly migratory European butterflies and a regular visitor to Hampshire and the Isle of Wight.  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.