Most of us think of spider webs as passive hunting tools: a spider spins a web, prey is caught in the web, the spider returns to collect its spoils. But for arachnids from the family Deinopidae, webs are used in a decidedly active (and decidedly terrifying) form of predation.
Commonly known as "gladiator" or "net-casting" spiders, these spindly legged beasties actually build cobweb sacks which are held open with the front legs and use to ensnare unsuspecting prey. It's absolutely remarkable to watch; in the video up top, David Attenborough narrates the activities of a net-casting spider as it prepares its gossamer pouch, and uses it to seize a cricket.
What's really remarkable about net-casting spiders is that, while the video up top emphasizes the species' keen visual abilities, new high-speed footage captured by researchers in Central America reveals that their hunting technique likely relies on tactile input as well. The video — which you can watch over at BBC — reveals that net-casting spiders may actually use thread like a trigger, springing into action when it physically senses that prey is near:
"The spider did not move a muscle until the antenna of that prey item, the cricket, touched the thread," explained researcher George McGavin, who witnessed the footage being filmed, in an interview with the BBC. "As soon as it touched it, [the spider] was on it in a thousandth of a second... if we hadn't had that camera, you wouldn't have seen a thing."
"It was the most exciting thing I've ever seen," he said. Exaggeration? Perhaps. But still pretty incredible. Check it out for yourself at BBC Nature.