What a Butterfly Sees Image 6
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What a Butterfly Sees (Image 6)

June 22, 2010
What a Butterfly Sees (Image 6) Ronald Rutowski can't see through this filter that blocks visible light and allows only ultraviolet (UV) light to pass -- but a butterfly can. Rutowski, an entomologist and behavioral ecologist at Arizona State University, uses the filter to photograph UV-reflective patterns on the insect's wings. Rutowski has been 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 virtually 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. Although butterflies cannot see detailed patterns, some species do rely on colors, particularly colors that are not visible to human eyes, to find and consider a mate. Rutowski found that virgin females of the Orange Sulfur (Colias eurytheme) species, are able to visually assess the relative age and fitness of competing males using UV scales on the males' wings and receptors in their eyes. These receptors allow the females to see UV wavelengths. Missing scales indicate aging and reduce a male's ability to seduce a mate. To learn more about this research, see "An Eye for Survival," in the ASU Research Magazine. This research was supported in part by the National Science Foundation. (Date of Image: 2001) [One of 10 related images. See Next Image.]

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