FlipFact of the Day: Despite the fact that there are no winged spiders, science has long been aware that some of these amazing arachnids can fly. They do so through ballooning, which is pretty much their version of paragliding: by crawling up to a high spot, raising their abdomens to the sky, and producing numerous silk fibers, they can “fly” towards more abundant sources of food or far away from predators. Spider ballooning is full of mysteries, though. For decades, scientists have tried to understand how these arachnids ride the wind—and recent findings suggest that Earth’s own electric currents may have something to do with it.
Prior to taking flight, spiders anchor themselves to their “launchpad” with a sturdy silk line. They then “tiptoe” by standing on the ends of their legs and lifting their bodies to test the wind. Once these arachnid aviators have verified that conditions are ideal for flight, they create triangular sheets out of silk fibers 2 to 4 m (6.6 to 13.1 ft) long and about 1/1000th the width of a human hair. Relative to the spiders’ silk gliders, the air is like a thick “fluid” that can easily counteract gravity’s effects.
Using these constructs, spiders can travel astonishing distances. They’ve been known to fly across seas and from island to island, and can even reach as high as 2.8 mi (4.5 km) in the air. And if wind conditions change, spiders can easily detach themselves from their silk parachutes and create new ones.
But what if there isn’t enough wind for liftoff? A 2018 study showed that ballooning spiders may also take advantage of our planet’s electrostatic forces to propel themselves into the air.
Upon exiting the spider’s body, spider silk tends to pick up negative charges, repelling the similarly negative charges of the platform the spider’s standing on. This is particularly effective when spiders are standing on leaves, grass, or branches; while plants have the same negative charge as the ground, the positively charged air around them can create electric fields that allow the spiders to take off. These electric currents may also help spiders determine how fast the wind is going, or the direction in which they’re flying, thanks to their microscopic hairs—an electrostatic “spider sense” of sorts.
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Cover photo: Robin Loznak/ZUMAPRESS.com /Alamy Live News