You don't need to be an expert to recognize luna moths(蚕蛾). They have hairy white bodies, red legs and huge green wings that stretch up to 4.5 inches across. And at the end of their wings are a pair of long tails that have attracted scientists for centuries.
Some of them theorized that it was possible that female moths judged the health and quality of a male by the size of his tails. But it turned out that female moths, were not choosy at all. They just mate with the first males they could find. Others believed that the tails could increase luna moths'size to make them harder for the bats—the main enemy of luna moths—to handle. But the theory proved wrong in 1903 when a scientist named Archibald Weeks put bats against a bigger species of moths that lacked tails. He found that the bats killed 66% of their targets. Luna moths, despite being smaller, were harder to catch. "Clearly, their tails provided an anti-bat atwantage, " Weeks observed. "I think they were used to direct bats away from the moths'body. "
He was roughly right. More than a century later, Jesse Barber from Boise State University put luna moths against bats in a dark room and filmed the hunting. Under normal circumstances, the bats only managed to catch 35% of the luna moths. But if Barber cut off their tails beforehand, the bats caught 81% of them. That was not because the moths became worse liers—in fact, cutting the troublesome tails seemed to have improved their flying abilities.
Barber explained that bats were not visual hunters. They found their food with a special sound. To be protected from bats, luna moths needed something that made confusing sounds. That was what the luna moths'tails did:As they flew, they waved behind them and produced sounds that were similar to their wing beats. To bats, they either sounded like a huge part of their target, or like an entirely different target. As a result, they aimed about half their attacks at the tails.
