The Clouded Yellow Colias
croceus is a resident but also a migrant to the oasis and farms of Eastern
Saudi Arabia where it feeds on alfalfa. It is sometimes very common but it is
uncertain if this is due to good breeding season or an influx of migrants as
they are strong flyers The species regularly undertakes long-distance
directional movements in large numbers and this is an essential strategy for
the species survival. The under-wings are a greenish-yellow colour with two
silver-white spots and this is normally all that can be seen on a resting
butterfly as they always rest with their wings closed. The upper-wings are deep
orange-yellow with broad dark wing margins. The genus has its origins in
temperate regions and is a genus of considerable antiquity. Its main centre of
development is in the high mountains of Asia and North America, it extends its
range to the tip of southern Africa and to Patagonia in South America.
