Spider Rain

Riding the Wind?

Terrifying or beautiful… or possibly both… no matter how you describe it, it’s nothing if not an utterly draw dropping experience. “Spider rain” is a rare occurrence in which thousands of spiders miraculously float through the air with their tiny strands of webbing floating just above them. The spiders can reach a height of up to 3 miles and can travel several hundred miles using this method. If you ever happen to experience the phenomenon it can be rather shocking as well as confusing. Spiders are flightless creatures, so how are they managing to rain down from the sky as though they were flying?

It was believed for a long time by curious onlookers and scientists alike that the sky-bound venture was possible due to wind currents creating enough lift beneath the spider silk that it allowed the spiders to ride air waves. However, this theory was recently disbanded when it was observed that spider rain can occur without even a slight breeze.

An Electric Journey

Upon further examination, it was discovered that electricity may in fact be the power behind the flight of these traveling arachnids. When preparing to take flight, the spiders will raise their rears and cast a sail-like formation of webbing into the sky. Wind or no wind, the spider will then shoot off at a rapid speed, climbing into the air.

Studies regarding this phenomenon started in the 17^th century along with some of the first documented cases of such terrifying occurrences. Shortly after, it was theorized that electrostatic forces may be behind the propulsion of the webbing, providing the necessary lift for the spiders to become airborne. This wasn’t considered in depth until 2013 in which a professor at the University of Hawaii looked into the logistics of the theory and formulated a detailed basis behind the claims.

This well-developed theory in accordance with future field studies on the subject hinge on the fact that the electric charge in the sky and on the ground differ from one another, forming an electric field regardless of the weather at the time (which would explain why spider rain can occur simultaneously with actual rain). This difference in electric charges at optimum levels can create the electric propulsion that affects the spiders’ webs similar to how your hair may stand on its end when introduced to static electricity.

The Study

In order to put this “shocking” theory to the test, scientists placed the spiders in two different controlled environments. The first environment purposely lacked any electric field and had no breeze disturbances of any kind, whereas the second environment introduced electric fields into the area. When they observed the spiders that were experiencing the induced electric fields, they noticed that the arachnids began raising their rears as they did when preparing to take off into the sky. The induced electric fields were then adjusted to different magnitudes and, once the field reached what the spiders appeared to deem as “optimal levels,” they shot out their silken sails and took flight.

The most incredible and irrefutable evidence from this study was observed once the spiders were airborne. The researchers began adjusting the electric magnitudes once again and were able to make the spiders rise higher into the air with increased electricity or lower them by turning the electric field down or even off.

Why do they do this?

Oddly enough, the spiders appear to test the wind with their legs prior to casting their silk to take flight. The hairs on the spiders’ legs are disturbed by electric fields in a unique fashion so as to differentiate the sensation from any wind interreference. This means that the spiders actively prepare for the flight and intend to make a journey when the conditions are optimal. Due to the drastic numbers that typically travel in a balloon of spider rain, it is assumed by scientists that the migration may be linked to a spreading out of adolescent spiders following their hatching.

Further Questions 

Several mysteries still surround the spider rain phenomenon including:

-Does wind still play a role in the spiders’ decisions to take flight even if it isn’t what causes them to lift into the air?

-How is spider silk electrically charged?

-Can the spiders control their flight in any way, and do they decide where to land?

It may be several more years before we are able to answer these questions. But the more we understand about the phenomenon, the easier it will be for scientists to predict when and where spiders will rain down from the sky next.

Citations

Green, H. (2018) Turns Out, Spiders Use Electricity to Fly, YouTube. SciShow. Available at: https://www.youtube.com/watch?v=x4ed7Y5Xffg&list=PLB3FCEEAC84884760&index=262 (Accessed: 2020).