Spiders known for elaborate circular webs have altered their spinning style in dark spaces to create apparent tripwires for walking prey.

Those that make circular webs are known as orb-weavers, and most of them trap mosquitoes, beetles and other flying insects in sticky spiral frame webs sparsely attached to outdoor structures, like tree branches. But European cave orb spiders (Meta menardi) anchor their webs to cave walls using twice as many silk strands, which appear to vibrate when tripped by unsuspecting crawlers, says Thomas Hesselberg at the University of Oxford.