Soaring spiders may get cues from electric charges in the air

Author: Laurel Hamers / Source: Science News

spider in — TIPPY TOES Before ballooning into the breeze, spiders adopt the “tiptoe stance” seen here, and release silk threads. New research suggests that spiders can sense electric fields and perhaps use them as a cue to balloon.

Spiders may lack wings, but they aren’t confined to the ground.

Under the right conditions, some spider species will climb to a high point, release silk strands to form a parachute, and float away on the breeze. Buoyed by air currents, they’ve been known to drift kilometers above Earth’s surface, and even to cross oceans to reach new habitats (SN: 2/4/17, p. 12).

Now, new research suggests air isn’t the only force behind this flight, called ballooning. Spiders can sense electrical charges in Earth’s atmosphere, and the forces exerted by these charges might be a cue for them to alight, researchers suggest July 5 in Current Biology. That invisible signal could help explain why spiders’ take-off timing seem a bit, well, flighty. Some days, arachnids balloon en masse; other days, they remain firmly grounded despite similar weather conditions.

Spiders with atmospheric aspirations do need a gentle breeze with speeds below around 11 kilometers per hour, past studies have shown. But those speeds alone shouldn’t be strong enough to get some of the larger species of ballooning spiders off the ground, says Erica Morley, a sensory biologist at the University of Bristol in England.