from the April 25, 2010 Newsletter issued from
Hacienda Chichen Resort beside Chichén Itzá Ruins, central Yucatán, MÉXICO
Some time back I sent Bea in Ontario a picture showing the side view of our most conspicuous yellow butterfly -- side view because as soon as this species lands it folds its wings together above its back. Bea replied that without knowing whether the top of the wings were white or yellow, she just couldn't decide which species it was. This week I managed to glimpse -- in a matter of maybe a tenth of a second -- flashes of white just before the butterfly landed. That's him above..
The white upper wings make this a White Angled-Sulphur, ANTEOS CLORINDE, found in many kinds of open, sunny, subtropical and tropical habitats from as far north (as irregular migrants) in the US as Nebraska and northeast Colorado, south through here all the way to Argentina. Just about anyplace in tropical and subtropical America you might run into this species. Its caterpillars feed on species of Cassia, in the Bean Family, and Cassia is a ubiquitous genus throughout the American hotlands.
The markings and venation on this species' underwings are so distinct that it seemed odd that to distinguish the species you'd need to know whether the wing tops were yellow or white. Bea sent the addresses of the two species in question, along with the remark that it's amazing that two species can look so similar from below, yet so different from above. You can compare them yourself, maybe using your split-screen feature:
WHITE ABOVE: Anteos clorinde - White Angled-Sulphur http://www.mariposasmexicanas.com/anteos_clorinde.htm
YELLOW ABOVE: Anteos maerula (Yellow Angled-Sulphur) http://www.mariposasmexicanas.com/anteos_maerula.htm