A silk string helps leaping spiders to land fast on their feet.

Jumping spiders, or salticids, can travel more than 20 times their body length in a single bound, usually with a dragline of silk, thought to function as a safety line, trailing behind them. Kai-Jung Chi at National Chung Hsing University in Taiwan and her colleagues showed that the dragline also provides stability, preventing the predatory spiders from pitching too far back through the air and so leaving them poised for action on landing.

Time-lapse images of the salticid Hasarius adansoni showed that spiders with silk (pictured; left panels) maintained orientation during jumps: they landed feet-first and were ready to pounce within about 10 milliseconds. Salticids that did not produce silk (right panels) landed on their abdomens, slipped or tumbled, sometimes requiring more than 50 milliseconds to regain their footing.

Credit: YUNG-KANG CHEN; KAI-JUNG CHI/JRSI

J. R. Soc. Interface 10, 20130572 (2013)