Migrants from North Africa and Southern Europe, Clouded Yellows usually appear in small numbers, but every so often conditions come together for large numbers to make the journey, so-called Clouded Yellow years. The vivid yellow shows up when they fly, which allows them to stand out even at some distance. You might get a chance to see that the upper wings of the males have dark borders, probably the origin of the clouded name. Some of the female Clouded Yellows seen on Alma Field might be confused with Large or Cabbage Whites when in flight because they have white upper wings and pale undersides to the forewings. Even with the fluctuations, the numbers of Clouded Yellows seen have risen steeply in recent decades.