Ascia is a genus of butterflies in the family Pieridae. It is monotypic, being represented by the single species Ascia monuste, commonly known as the great southern white, In this species the sexes may differ with the female being either light or dark colored. It is found from the Atlantic and Gulf coasts of the United States, and south to Argentina. It is migratory along the south-eastern coast of the United States, with strays to Maryland, Kansas, and Colorado.

Larvae have distinct body segments within which there appears to be four to six subsegments. They are purplish-green with two longitudinal, greenish-yellow stripes on each side and the dorsal side. When full-grown, they are approximately one and a quarter inches long. The wingspan in adults is 63–86 mm. Adults are on wing all year round in southern Texas, peninsular Florida and along the Gulf Coast.

A. monuste is a migrating species that moves in one direction within its life span and does not return. It breeds in Florida but sometimes migrates along the coast up to 160 km to breed in more suitable areas.

...