For humans, attractiveness is determined by the symmetry of our features, but a study to be published online tomorrow in Biology Letters proposes that lopsided legs help males of a newly identified species of dance fly called Empis jaschhoforum to attract a mate. Researchers examined 33 male flies captured on Mount Fuji in Japan, and found that 14 of them had one inflated, balloonlike leg. One possible explanation is the presence of parasitic worms, but none were found in the 10 samples that the team dissected. Instead, the researchers speculate that inflated legs help attract females from afar, as the legs of other species of dance fly are known to play an important role in courtship and mating.
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