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The Sulphur Butterflies documents the 1970s field research of lepidopterists Bob Silberglied and Chip Taylor in alfalfa fields of southwest Arizona. These study sites were populated with incredibly dense population of butterflies from two closely related species of Colias butterflies. Silberglied and Taylor studied in depth how females recognize the males of their own species based on ultraviolet coloration. This movie features the original footage that was intended as a companion to a scientific article on sexual selection in these two species, and was retrieved in the Smithsonian Institution archives 35 years after the untimely death of Bob Silberglied in a plane crash at the age of 35.
