By Susan Milius
Unlike the guy with two left feet, males of a new species of dance fly from Japan’s Mt. Fuji often grow feet that don’t match at all.
Dance flies are named for their erratic flight moves in mating swarms. Males of the new dance fly species can grow asymmetric front legs, one an unsurprising slim fly leg and the other ornamented with what looks like a little tufted balloon, says Christophe Daugeron of the French national research agency CNRS and the National Museum of Natural History in Paris. He and his colleagues give the fly an official scientific name, Empis jaschhoforum, in a paper released online the week of September 20 in Biology Letters.
Comparing the new fly’s ornaments to balloons isn’t unreasonable, since some of the hundreds of known dance fly species woo potential mates with little balloons of silk secreted from glands in their feet, says Adrian Plant, a coauthor of the paper and curator of the fly collection at the National Museum of Wales in Cardiff. Depending on the species, flies present bits of prey in balloons or sometimes just pretty, empty balloons. Sometimes moderately flashy flies win the most mates, suggesting that a lot of bling attracts attention from a distance but interferes with flying up close.