Here’s why some water striders have fans on their legs | Science News


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Here’s why some water striders have fans on their legs

The appendages help the insects navigate flowing water

2:30pm, November 3, 2017
fan from water strider leg

FAN GAME  This feathery fan, seen here magnified, snaps open and shut on the legs of insects called Rhagovelia water striders, helping them traverse flowing water.

For an animal already amazing enough to walk on water, what could growing feather fans on its legs possibly add?

These fans have preoccupied Abderrahman Khila of the University of Lyon in France, who keeps some 30 species of bugs called water striders walking the tanks in his lab without getting their long, elegant legs wet.

“Walk” may be too humdrum a word. The 2,200 or so known species of water striders worldwide can zip, skim, skate and streak. Among such damp-defying acrobats, however, only the Rhagovelia genus grows a fan of delicate feathers on the middle pair of its six legs. Even little hatchlings head-banging their way out of underwater eggs have a pair of feathery microfluffs for their perilous swim up to cruise the water’s surface.

A first guess at a function — maybe plumes help support bigger adults — would be wrong, Khila says. The Rhagovelia are not giants among water striders. In a jar of alcohol in his

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