Spiders May Harness Electric Currents to Fly

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Closeup of a spider ballooning from a plant.
A baby goldenrod crab spider balloons from a cardoon flower petal. (Photo: thatmacroguy/Shutterstock)

Somewhere at this very moment, there's a spider floating high above the Earth, like an eight-legged astronaut, looking for a good place to land.

We know that spiders can sail the friendly skies using a process called ballooning. It's simple, yet ingenious: a spider climbs to a prominent spot, waves a tiny parachute from silk and catches a breeze.

And off they sail for a bold new world, in hopes of bountiful prey and maybe even fewer predators.

It would seem like a remarkably efficient way to cover vast distances, with some spiders spotted as high as 16,000 feet above sea level.

The only catch? The laws of aerodynamics shouldn't let spiders catch a breeze to sail such massive distances — no matter how light and airy those silken parachutes may be.

In fact, a new study suggests, spiders probably get a hand from the Earth's electrical field. That's the charge the Earth builds up as it moves and interacts with the atmosphere and ionosphere. Essentially, the planet's atmosphere is a massive electrical circuit — and spiders may have built-in equipment for detecting where fields are strongest, and tapping into it.

At least that's what Erica Morley and Daniel Robert, researchers at the University of Bristol, concluded after watching spiders in an electrically charged box get airborne — even when there was no breeze.

"This is really top-notch science," physicist Peter Gorham told The Atlantic. "As a physicist, it seemed very clear to me that electric fields played a central role, but I could only speculate on how the biology might support this. Morley and Robert have taken this to a level of certainty that far exceeds any expectations I had."

Spider seen in the air with a blue sky in background
Spiders have been spotted soaring as high as 16,000 feet above sea level. Ademortuus/Shutterstock

But first, to understand how spiders may ride the proverbial lightning, we need to understand a few basics about the Earth's electrical field. The planet has a negative charge. It's the very literal definition of being "grounded." The atmosphere, on the other hand, has a positive charge, with the air, on non-dark and stormy days, packing around 100 volts of electricity per meter on the ground.

Now, when a spider slings a web, that strand is negatively charged. As such, it repels the negative charge of whatever other ground-based object the spider happens to be perched on. The air around that web, on the other hand is positively charged. In effect, an electrical circuit is created.

Being able to harness that energy for travel — a process known as electrostatic repulsion — may come down to a very special spider sense: Researchers noted tiny hairs on spiders' feet that quivered in the presence of an electrical field.

"Spiders have a lot of spines and other kinds of hairs. But it's this one particular kind of hair — called trichobothria — that was moved in the electric field. The other ones didn't seem to move at all," Morley told PBS.

Close-up of a spider
The hairs on a spider's legs can detect sound, air currents and possibly even electrical fields. Protasov AN/Shutterstock

But more than just sensing the presence of an electrical field, some spiders tapped into it by weaving their mini-parachutes and taking to the air, even from their little plastic box.

In other words, they could not only detect electrical fields, but use them — and the principle of electrostatic repulsion — to achieve lift-off.

Now, imagine the kind of heights spiders can reach when there's a lightning storm and the atmosphere crackles to the tune of several thousand volts.

And maybe, if you're an arachnophobe, despair a little.

Because these riders on the storm may drop in from just about anywhere.