Planing spiders can obtain electrical charge signals in the air

Spiders may lack wings, but they are not confined to the ground. Under good conditions, some species of spiders will climb to a high point, release silk strands to form a parachute and float in the wind. Worn by the currents of air, they are known to derive kilometers above the surface of the Earth and even to cross the oceans to reach new habitats ( SN: 2/4/17, p .12 ). , new research suggests that the air is not the only force behind this flight, called ballooning. Spiders can detect electrical charges in the Earth's atmosphere, and the forces exerted by these charges could be an indication for them to arise, the researchers suggest on July 5 in Current Biology . This unseen signal could help explain why the take-off timing of spiders seems a little, well, fickle. Some days, arachnids go up in droves; on other days, they remain firmly anchored despite similar weather conditions.

Spiders with atmospheric aspirations need a light breeze with speeds below about 11 kilometers per hour, according to previous studies. According to Erica Morley, sensory biologist at the University of Bristol in England, these speeds should not be enough to take off some of the largest balloon spider species

Scientists have long wondered if another force might be involved: Perhaps the electric charges in the US are the same. Earth's atmosphere grow against silky yarns These electric charges form an electric field that attracts or repels other objects or charged particles, which varies in strength, becomes stronger around objects such as leaves and branches on trees and also fluctuates with meteorites.In the first experimental test to determine whether spiders can detect these electrical charges, Daniel Robert, a sensory biologist from Morley and Bristol, has blocked natural electric fields in a laboratory and created a Artificial field imitating future arthropods.Experience, and placed the tiny spiders of the family Linyphiidae in this false field.Under the electric field, even e without breeze, the spiders pe on the ends of their legs, a behavior similar to that of the ballerina that precedes the swelling. When the researchers quenched the artificial electric field, the behavior (which scientists call the "tiptoe position") faded away.

Tiny hairs on the bodies of spiders react to the air and the presence of an electric field. . The hairs stood as long as the air blew over them. But when they were facing an electric field, they were most spectacular when the field was lit, then gradually deflated to their rest position for about 30 seconds.

The study relates tiptoe behavior to the presence of one According to him, Moonsung Cho, a researcher in aerodynamics at the Technical University of Berlin, who did not participated in the study, may need it. While some spiders in the study floated away, this takeoff behavior was not really measured.

And answering electric fields is probably not the complete story when comes the time of takeoff: a different kind of spider, Xysticus or crab spiders on the ground , seems to feel the speed of the wind with his paws before ascending, waving a fusiform appendage to feel the air moving and determine if the wind conditions are favorable for takeoff, reports the Cho team in PLOS Biology .