12 September 2022
Mainland spiders are found on remote islands 400 miles from the nearest land and have been noted by ships 1,000 miles at sea. How did they get there?
When baby spiders (spiderlings) disperse and when lightweight species really want to go places they wait for a light wind and electrically charged air. When conditions are right they stand on a high exposed spot on extended legs, tip up their back ends, and eject several gossamer threads from their spinnerets.
The silk automatically forms a lightweight triangular shaped parachute and, because its electrical charge matches the ground and is opposite to the air, it’s repelled from below and pulled into the sky. The gossamer parachute rises up and away and drags the spider with it. And he’s off! Flying backwards thanks to static electricity.
This action, called ballooning, can carry an individual spider at least 1,000 miles on a light wind and two to three miles above the earth (10,500-16,000 feet). The spider can stay airborne over open ocean and thus colonize an island.
Not all spiders go ballooning but the species that do, like the trashline orbweaver (Cyclosa turbinata) pictured at top, have quite a wide distribution.
How can you tell that tiny spiders have been flying? When you see lots of spider silk clinging to branches in a light breeze you’ve found the aftermath of a mass ballooning event.
Read more about spider ballooning at Ask Nature: Spiders Fly Riding Electric Current and at Spiders Colonized A Remote Pacific Island By Flying There.
See the original University of Bristol study, July 2018, at Science Direct: “Electric Fields Elicit Ballooning in Spiders”.
(photo credits are in the captions, click on the captions to see the originals)