July 20, 2018
spiders adopt a posture
shown here called "tiptoeing."
Did you know that spiders can fly? Biologists call it "ballooning"...
Spiders spin a strand of silk, it juts into the air, and off they go. Airborne arachnids have been found as high as 4 km off the ground. Originally, researchers thought spiders were riding currents of air, but there's a problem with that idea. Spiders often take flight when the air is calm, and large spiders fly even when air currents are insufficient to support their weight.
It's a mystery...
In a paper (Electric Fields Elicit Ballooning in Spiders) published in the July 5th edition of Current Biology, they proved that spiders can propel themselves using electric fields.
This diagram, borrowed from K.A. Nicoll's review paper
illustrates the role of thunderstorms and cosmic rays
in creating Earth's electric fields.
A remarkable below video of their experiment shows one spider flying when the fields were switched on, then sinking when the fields were off again.
In a nutshell, thunderstorms help build up a charge difference between the ground and the ionosphere 50 km overhead. The voltage drop is a staggering 250,000 volts.
This sets up electric
fields linking Earth to the edge of space.
Cosmic rays ionize
Earth's atmosphere, turning it into a weak conductor that allows
currents to flow through the GAEC.
Peter W. Gorham of the Dept. of Physics and Astronomy at the University of Hawaii notes that,
a spider flying in respond to laboratory electric fields.
Charles Darwin may have been the first. He wrote about it during his voyages on the HMS Beagle (1831-1836).
One day, the ship was 60 miles off the coast of Argentina when the deck was inundated by ballooning spiders.
He was particularly struck by spiders using multiple strands of silk that splayed out in fan-like shapes. Instead of tangling as they moved through the air, the strands remained separate.
Were they repelled by an electrostatic force? Darwin wondered in his writings.
The work (Electric Fields Elicit Ballooning in Spiders) of Erica
Morley and her collaborator Daniel Robert closes the loop
on a train of thought almost 200 years old.
twitch when electric fields are present
– a signal to the spider that ballooning may commence.
"Electric Fields Elicit Ballooning in Spiders"
Research groups have demonstrated connections between space weather and atmospheric electricity on a variety of time scales:
Could the migration patterns of ballooning spiders be affected by space weather?