Zebra Stripes Evolved to Repel Bloodsuckers?

Conventional wisdom says a zebra's black-and-white stripes camouflage the animal in tall grass—the better to evade the colorblind lion. But a new study says the pattern scrambles the vision of a tinier biter: the bloodsucking horsefly.
Horseflies, the females of which feed on blood, are attracted to polarized light—light waves that are oriented in a particular direction and that we experience as glare. This glare lures the bugs most likely because it resembles light reflected off water, where they lay their eggs.
On horses, black fur reflects polarized light better than brown or white, as evolutionary ecologist Susanne Åkesson and colleagues found in a previous study.
The researchers therefore assumed that zebra coats, with their mixtures of light and dark stripes, would be less attractive to flies than those of black horses but more than those of white horses.
But after experiments in which they team measured the number of horseflies that became trapped on gluey, striped boards or models of horses, the team found that zebra stripes are the best fly repellent—and the narrower the stripes the better.
The results may help explain why zebras' skinniest stripes are on their faces and legs. "That's also the place where you have the thinnest skin," said Åkesson, of Sweden's Lunds University.
But why would striped skin be more effective than white, which has the lowest refectivity of polarized light?
The black-and-white pattern, Åkesson said, turns out to be "ideal in its function of disrupting this signal of reflected polarized light."
Because the coat reflects light in alternately polarized and nonpolarized patterns, the zebra "is more difficult to single out relative to the surroundings." It is, in effect, camouflaged to flies as well as to big cats.