Size doesn’t matter, at least not the size of the eyespots on a male butterfly’s wings when female butterflies consider potential mates.

Instead, females are attracted to the “sparkle” created by the ultraviolet reflectivity of the pupils, the white circles at the center of eyespots, according to new research from UB biologists. The research overturns previous work, the results of which indicated that larger eyespots might be considered more desirable by female butterflies. The purpose of the recent research at UB was to explore some of the evolutionary reasons behind butterfly wing patterns in the African satyrid butterfly, Bicyclus anynana.

The findings were surprising in the context of the natural world, where dramatic colors and physical features often win the sexual-selection game, according to the researchers. “This is one of the first studies to show that such a small pattern element really matters in female choice,” says Antonia Monteiro, a coauthor on the paper and UB assistant professor of biological sciences.

The research was funded by the National Science Foundation.