Spiders can also "take off" when there is no wind, relying on the "electric field"

Spiders' aerodynamic abilities have plagued scientists for hundreds of years. Scientists define the flight behavior of these wingless arthropods as "ballooning," in which spiders can use spider silk to push themselves into the wind and migrate thousands of miles. However, "balloon driving" can also be seen when there is no wind, cloudy days or even rain, which begs the question: how do spiders "take off" at very small aerodynamic resistance?

In a paper published July 5 in the journal Current Biology, biologists from the University of Bristol in the United Kingdom believe they have found the answer. "Many spiders release multiple silks during 'takeoff', and these silks are fanned out, which means that there may be a repulsive electrostatic force between them." Dr. Erica Morley, an expert in sensory biophysics and principal investigator, said, "Existing theories cannot predict the 'balloon driving' pattern of spiders that use only wind as power. Why do some days there are a large number of spiders taking off, but in other days there is not a single one? We wondered if there were any other external forces besides aerodynamic drag that triggered 'balloon driving' and what kind of sensing systems spiders used to detect these forces? ”

The mystery could be an atmospheric potential gradient (APG). Insects can detect atmospheric potential gradients and electric fields around all matter. For example, bumblebees can detect the electric field that appears between themselves and the flowers, and the bees can communicate with the hive with an electric charge. Spider silk has long been thought to be an effective electrical insulator, but until now, it was not known that spiders are able to detect and respond to electric fields in a manner similar to bees.

In their study, researchers at the University of Bristol exposed the spider to an experimentally controlled electric field (in proportion comparable to the electric field present in the atmosphere) and found that when the electric field was turned on or off, the spider would move up (on) or down (off), demonstrating that in the absence of wind, the spider could "take off" in the electric field.

"Previously, scientists thought that the dragging force from the wind and the spider itself was the driving force of this dispersion, but our research showed that the electric field can cause 'balloon driving' and provide lift for spiders when the air is not flowing." Dr Morley added.

The scope of application of these discoveries is not limited to the arthropod world, and airborne dispersion is also a very important biological process for many animals such as caterpillars. A better understanding of the mechanisms behind this mode of dispersal is important for the global ecology to better describe population dynamics, species distribution, and ecological restoration. "In the next step, we will investigate whether other species of animals can also detect and use electric fields to travel through the air." Dr. Morley said.

Editor: Sky Reviewer: alone Editor: Zhang Meng

Source: https://phys.org/news/2018-07-spiders-ballooning-electric-fields.html