By Susan Milius
A family of spiders can catch prey many times their own weight by hitching silk lines to their quarry and hoisting the meaty prize up into the air.
Tangle web spiders, in the Theridiidae family, are masters of using silk to amplify muscle power. Their webs are “a messy tangle,” says Gabriele Greco, who studies biological materials at the University of Trento in Italy. Silk strands slant and crisscross in a cobwebby scribble.
Filming how spiders hunt from such snarls, Greco and Trento colleague Nicola Pugno focused on the most spectacular scenarios: attacks on insects that weighed up to 50 times as much as the spiders themselves. The web makers, however, could win their battles, thanks to adroit fighting, venom and lots of prey-wrapping silk. Victorious spiders also attached multiple silk threads to their prey bundle to haul the feast up to the web, Greco and Pugno report February 3 in Journal of the Royal Society Interface. Yet oddly these threads never get pulled totally taut.
To analyze the spiders’ weight-hauling moves, the researchers set up lab boxes with black walls for easy observation of white silk. Inside each box went a Theridiidae species, either a triangulate cobweb spider (Steatoda triangulosa) or a false black widow (S. paykulliana).