How Spiders Surf the Wind For Miles on Strands of Silk

Spiders may very well be hairy and scary, but at least they can’t fly … right? Well, that depends on your definition of flight. As The New York Times reports, new aeronautical research is shedding light on the little-understood phenomenon of “ballooning,” which lets spiders span great distances—even oceans—by riding the wind like paragliders.

Moonsung Cho, an aeronautical engineer, started researching “spider flight” after witnessing a spider being carried by the wind in Denmark. Scientists have long known that spiders sometimes use flight to evade threats or seek food and mates in other locations, but prior to this study, the physics of how it actually works remained fuzzy.

Cho and his colleagues brought crab spiders back to the laboratory and used a wind tunnel to observe their response in a controlled setting. They discovered that a spider will use its leg as an anemometer, lifting one limb to test the strength of the wind. (Their idea of perfect flying weather is a light breeze of about 7 mph.)

Then, the spider lifts up its abdomen, shoots strands of silk skyward, and lets itself be carried off into the sunset. These strands of silk are far thinner than a strand of human hair and can measure up to 6 feet long. As Live Science puts it, a strand of silk contorts when it’s caught in the wind, thus “catching air like an open parachute.” This lets spiders surf the air current, at least for a few miles.

Instances of “spider flight” have been witnessed all over the world. Residents of one Australian town reported seeing a “tunnel of webs” in the sky back in 2015. Spiders sometimes migrate en masse, and although they use the wind to move about, they can’t control where they end up. Some have even landed on islands in the middle of the ocean.

Check out this video from The New York Times to learn more ballooning.

[h/t The New York Times]