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I just witnessed a small jumping spider jump on some kind of louse or bed bug on the ceiling. How does it do that without falling? I have yet to find a high-speed-camera video of a jumping spider jumping on a ceiling.

My hypothesis is that the spider would spit silk and anchor it on the ceiling, then jump, and allow itself to be swung by the silk onto the prey. But I don't have a high speed camera to prove that.

EDIT: I now have some evidence that supports my hypothesis: I just saw a jumping spider attempt to jump on a prey and failing to land properly. It didn't fall directly to the floor. Instead, it dangled from its own silk, at about 2 cm from the ceiling, then climbed right back up the thread of silk, onto the ceiling.

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Whilst I've seen no evidence either, your hypothesis that the spider uses its silk seems highly likely; small spiders are known to 'balloon', using their silk to float through the air en.wikipedia.org/wiki/Ballooning_(spider). Using their silk to 'pounce' on prey seems very plausible. –  Luke Jul 9 '12 at 13:15
    
good work using observation btw... that's how all science starts... –  shigeta Feb 27 '13 at 13:57
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up vote 4 down vote accepted

You are right - most jumping spiders have draglines they secure to the surface before they jump. They can't defy gravity, but they can recover from a miss if they do this.

Disturb a jumping spider on a wall, and watch it seemingly defy gravity: it will jump horizontally out into the air, then return to the wall. This seems fantastic until you spot the major ampullate dragline. It essentially becomes the bob at the end of a pendulum string.

the book goes on to explain that the dragline is used as an airbrake and a spring to help the spider control the jump, which might make it seem to do unnatural things when jumping from a ceiling. You might want to get a video of this if you can.

Some of the references in another book here, point to other uses of draglines - the spiders can tell each other's species by them, attract a mate.

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