While the male of this species is a beautiful clear cloudless yellow, the female is more orange in color and has dark markings, particularly on the wing borders. These large sulphurs are the fastest of all the Pierids, flying swiftly along the roads anywhere from southeastern Canada clear to South America. To seeing a racing auto converging on you down a highway, for the first flash of its wings is hardly observed before it is upon you, then away it goes in great swings from side to side that carry it quickly out-of-sight.
While in our own land, the Cloudless Sulphur is noted for its northward migration in the early fall, in the tropics it also makes strange and frequent migrations of hundreds of miles. During these migrations, dozens of the butterflies sometimes gather at a single muddy pool on a dirt road, and, at such times as these, or when sipping blissfully the nectar of the flowers, they are fairly easy to catch.
This sulphur has one of the prettiest of all caterpillars, with alternate bands of light blue and yellow, the yellow marked with orange dots. It feeds on senna plants, and clovers. The chrysalid has a most fantastic shape, looking like a little greenish-yellow man with a peaked green cap and a big fat belly, striped with brown.