Colia Eurytheme on Saint Vincent and the Grenadines stamp

Colias eurytheme or The Orange Sulphur, also known as the Alfalfa Butterfly and in its larval stage as Alfalfa Caterpillar, is a butterfly of the family Pieridae, where it belongs to the "yellows and sulphurs" subfamily Coliadinae. It is found throughout North America from southern Canada to Mexico, but is absent from the central and southeastern USA.
Colias eurytheme belongs to a lowland group of clouded yellows, Colias. The Orange Sulphur's caterpillars feed off various species in the pea family (Fabaceae) and are usually only found feeding at night. Occasionally this species multiplies to high numbers, and can become a serious pest to Alfalfa (Medicago sativa) crops.