Colias four species (IMAGE) George Washington University Caption The male species of the orange sulphur butterfly (Colias eurytheme, top right) is the only one to display UV iridescence in nature. The female of the same species (top left) and both the female and male of the clouded sulphur butterfly (Colias philodice, bottom left and right) do not display UV iridescence due to the presence of a speciation gene on a sex chromosome. Credit Vincent Ficarrotta and Arnaud Martin/ The George Washington University Usage Restrictions With GW permission only. License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.