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A male, large orange sulphur (Phoebis agarithe) butterfly, as it appears to the human eye. This species has a wingspan of about 6 centimeters and is common in the American tropics and subtropics. Ron Rutowski, an entomologist and behavioral ecologist at Arizona State University, is studying butterfly vision.
Butterflies are very nearsighted. While they can spot color and conspecifics, they cannot recognize patterns. In addition, their vision is monocular, not binocular like humans, making them unable to assess depth or distance in the same way we can. However, nature has made up for this in other ways. Some species of butterflies, like the empress Leilia (Asterocampa leilia), have a visual field of about 344 degrees on the horizontal plane--only 16 degrees short of seeing all the way around its body. And vertically it is almost a full 360 degrees. The average human has a visual field of only 190 degrees. This wide field of vision helps protect them from predators, particularly birds. Most butterfly species have visual fields that are equally impressive.Image credit: Ron Rutowski, Ph.D.
