A redback spider with a small lizard trapped in its web

How can such a tiny spider lift a whole lizard?

Image: Wikimedia commons/Calistemon CC-BY-SA 3.0

Imagine you’re a tangle-web spider, and you’ve just snared a nice big critter for dinner. Sounds great, huh? Except there’s a problem. Dinner is 50 times heavier than you, and it’s trying to escape. What’s a spider to do?

Turns out tangle-web spiders have a handy technique for lifting heavy prey, and it’s been captured on video by European scientists.

The action starts after a cockroach blunders into the spider’s sticky trapping threads. The spider climbs down from its web, trailing a strand of spider silk. The silk is stretched like a rubber band, and stuck to the helpless cockroach. One thread isn’t strong enough to do much, but the spider isn’t running out of silk any time soon.

Over the next few minutes, the spider climbs up and down sticking more and more stretched threads to the cockroach. Eventually, the pull of all these stretchy strands is enough to lift the cockroach off the ground, and up to the spider’s home. The energy in the stretched silk does the heavy lifting. It’s a bit like lifting a car off the ground with ten thousand rubber bands.

The scientists ran several experiments with two species of tangle-web spider and both species used this technique. This was a small study, but it’s likely other tangle-web spiders use the technique too.

Tangle-web spiders can be found all around the world. The redback is a famous Australian tangle-web, and there are photos of large prey – including lizards – snared in their webs. Now we’ve got a better idea how those poor critters got stuck there!

Video: Dr Gabriele Greco, University of Trento

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