SOME spiders can take to the air, moving hundreds of kilometres with the winds. Now we know how they do it: they make 鈥減aragliders鈥� from ultra-thin fibres.
Many kinds of spider travel through the air with the help of silk fibres that act like paragliders. There has been no mystery about how lighter spiderlings fly, often taking to the air soon after hatching to avoid being eaten.
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But it has been hard to explain how larger spiders do it. They were thought to release only a few thick, short fibres, which in theory shouldn鈥檛 give enough lift.
To solve the mystery, aerodynamic engineer Moonsung Cho at the Technical University of Berlin and his colleagues observed adult ground crab spiders of the genus Xysticus in a wind tunnel and in a park.
They found that before taking off, the spiders anchor themselves with a safety line and lift a leg to test the wind. If conditions are right, the spiders quickly spin fibres 2 to 4 metres long that form triangular 鈥渟heets鈥� to catch the wind.
Two of the fibres are made from relatively thick silk 鈥� probably those that other biologists have observed. But the spiders also spin 50 to 60 fibres of much thinner silk, which provide more than enough lift (PLoS Biology, ).
This article appeared in print under the headline 鈥淢ystery of spider flight solved鈥�