This Clever Spider Hurls Itself at Prey Using Its Web as a Slingshot

The triangle-weaver spider flings itself at its prey, wrapping it up for dinner in the blink of an eye. Sarah Han/University of Akron/CC 2.0

Some spiders really know how to weave a nightmare.

Take, for example, the triangle weaver. Ever so slowly, these spiders — so-named for the shape of the webs they weave — pull a strand of silken webbing until it's nice and tight. Then, when unsuspecting prey gets within range, they fling themselves through the air like a bolt from a crossbow. Or, if you prefer, a pebble from a slingshot. Or a — oh, does it really matter? There's a hairy, leggy, eyeball-addled spider shooting through the air!

The predator lands, with unerring accuracy, near the victim — effectively telling that hapless creature there's no need to venture into its web. This spider will take its nightmare to you.

We can thank researchers at the University of Akron for adding fresh grist to our collective nightmare mill. They detailed the triangle weaver's deadly designs this week in a research paper published in in Proceedings of the National Academy of Sciences.

The spider, they noted, achieves rocket-like acceleration by leveraging its stretchy webbing, a phenomenon they call "elastic recoil." The spider taps into the elasticity of its webbing to augment its own power, creating "much larger forces and therefore much larger acceleration," study co-author and physicist Daniel Maksuta tells NPR.

In that sense, the spider is using its web as a tool, not unlike the way humans do. But triangle weavers seem to have honed their strategy to lethal perfection.

A triangle-weaver spider preparing to use its web as a slingshot.
In this very close-up image, you can see how the spider anchors the line with its back legs, stretching and tensing it for maximum flinging power. Sarah Han/University of Akron

As described in the study, the spider fires its body toward its prey in short bursts of no more than an inch. But it does so at the torrid speed of more than 700 metres per second. That's nearly 1,600 miles per hour. Or 400 of the spider's body lengths per second.

Stopping suddenly from that speed causes as many as four more sticky threads to fly forth from the predator at equally alarming speed. In an instant, the fly is not only staring at a spider but fully entombed in the webs that burst from its body.

"The rapidly moving web tangles around the prey insect, starting the capture process from a distance," University of Akron biologist Sarah Han tells AFP.

With dinner bagged, the only decision the spider has to make is whether it will be dine-in or takeout.

As you might imagine, one of the biggest challenges for the research team was trying to record the triangle weaver's lightning-fast maneuver in a controlled setting. While the spider can easily be seen holding its "sling" taut for hours at a time, the moment it moves looks less like locomotion and more like teleportation to the naked eye.

For the study scientists found their subjects literally hanging around the university. They brought them into the lab and invited them to build homes in the terrariums they provided.

Then they unleashed perhaps the most unfortunate research subjects of all time: flies. That's where high-speed cameras and a battery of motion-sensing technology took their cue.

"We were recording all of this with high-speed video cameras," Han explains to NPR, adding that they used "motion tracking and software to get the position data, and from that we can get things like velocity and acceleration."

That velocity and acceleration proved astonishing. Although the principle behind it, called power amplification, has long been used by bow- and slingshot-wielding humans, it's the first time we've seen spiders harness it.

"This finding reveals an underappreciated function of spider silk and expands our understanding of how power amplification is used in natural systems, showing remarkable convergence with human-made power-amplifying tools," the authors wrote in the study.