For years, scientists have pondered over spider ballooning or the capability of the creatures to go airborne by releasing trails of silk that allows them to use air currents to their advantage and fly from one point to another.

The phenomenon has been observed on a number of occasions, but sometimes, it was also noticed that spiders balloon away even when it’s raining or there is no breeze to use at all. This, as a new study suggests, is the outcome of an atmospheric electric field, which helps these arthropods stay aloft up to 4 km (2.48 miles) from the surface.

Ballooning Spide
New study shows spiders use natural electric field to balloon. Pictured, a ballooning spider showing a tiptoe stance on a daisy. Michael Hutchinson

Over the years, scientists thought some external force might be helping the creatures fly even without suitable aerodynamic drag. Several theories were proposed but the exact answer wasn’t found until a group of researchers from University of Bristol conducted a series of experiments with spiders.

“Why is it that some days there are large numbers that take to the air, while other days no spiders will attempt to balloon at all?,” Erica Morley, the lead author of the work, said in a statement. “We wanted to find out whether there were other external forces as well as aerodynamic drag that could trigger ballooning and what sensory system they might use to detect this stimulus.”

Among different theories explaining spiders’ weird capabilities, one suggested the creatures might be using some kind of electrostatic force prevailing in the atmosphere to propel themselves. The idea was posited some five years ago and was put to test by Morley and team.

As it was already well established that some insects can detect atmospheric potential gradient (APG), which serves as a global circuit and is always present in the atmosphere, the group collected a few spiders using a trap and exposed them to controlled electric fields to see their response.

The electric field from APG maintains potential of 120 volts per meter on a clear day, but gets 10 times stronger during thunderstorms. So, the group went ahead with that potential and created an electric field very similar to that the found in nature.

In the test, as they switched the field on, the spiders started ballooning and went airborne, a fact that suggested electrostatic forces from the field was enough to propel them. When the field was turned off, the spiders came gliding down and couldn’t take off.

The researchers also used lasers to show the spiders could be using the hairs present on their legs to detect the field and use it to their advantage.

“Previously, drag forces from wind or thermals were thought responsible for this mode of dispersal, but we show that electric fields, at strengths found in the atmosphere, can trigger ballooning and provide lift in the absence of any air movement,” Morley concluded. “This means that electric fields as well as drag could provide the forces needed for spider ballooning dispersal in nature.”

The study titled, “Electric Fields Elicit Ballooning in Spiders,” was published July 4 in the journal Current Biology.