Spiders Can Fly Thousands Of Miles By Harnessing Earth's Electric Fields, Research Finds
Spiders can float for thousands of miles using their silk, but there's more to it than just using their intricate web like a parachute.
Ballooning: The Basics
In a process called ballooning, arachnids go airborne by climbing to a relatively high point, raising their abdomen, producing silk, and floating away for miles and miles.
An easy explanation is that the wind simply carried the "balloon" away, but as the Atlantic notes, this makes little sense since spiders only take to the air during gentle winds. It's unlikely these light breezes can provide ample lift and acceleration for adult spiders, especially over great distances.
Now, new research provides a clue to the answer: it turns out the Earth's electric field is closely intertwined with the arachnid's ability to fly.
Spiders Fly With Some Electric Help
The study, published in the journal Current Biology, reveals that spiders can respond to the electric field and use it during the ballooning process.
"We don't yet know whether electric fields are required to allow spider ballooning," Erica Morley from the University of Bristol explains in a statement. "We do, however, know that they are sufficient."
Earth's electrical circuit is ever present, caused by the thunderstorms occurring throughout the world every day. On a sunny, clear day, the charge or atmospheric potential gradient can be around 100 volts per meter above the ground. During thunderstorms or when there are charged clouds, this can shoot up to 10 kilovolts per meter.
To see whether spiders respond to this electrically charged field, Morley and colleague Daniel Robert took spiders from the Erigone genus to the laboratory where there's no other stimuli that can spur its flight such as air movement. Then the team turned the electric fields on and off in order to see the spiders' reaction to it.
They found that spiders respond to the APG-like electric fields by ballooning. In particular, the tiny sensory hairs on the spiders' exoskeleton called trichobothria move in response to the electricity in the air. Morley and Robert suggest these allow the spiders to actually detect the electric field.
Once the spiders are in the air, turning the electric field on and off drove them to float up and down, respectively.
These new findings can help scientists more accurately predict ballooning behavior in spiders as well as other animals who exhibit the ability such as caterpillars and spider mites.
Fibers Also An Important Factor
Aside from the electric circuit of the Earth, the fibers that spiders spin are also a significant part of being able to fly.
A study published in PLOS Biology last June explains that contrary to the belief that adult spiders only use a few thick fibers for ballooning, they actually produce two different kinds: a few strands of thick one and dozens of a far thinner fiber. This unique combination is enough to carry a heavy spider over miles and miles.