Airborne spiders dropping into a lake or sea aren't sunk, new research shows: in fact, they seem to take to water like old salts, setting sail with raised legs and using silk to slow or anchor themselves.
Many arachnids travel great distances by "ballooning.": They spin out a thread of silk and allow the wind to catch it — with them attached. The wind whisks the thread and the spider miles away, far from predators or competitors.
Scientists had thought that if the wind happened to carry the spiders onto a body of water, the bugs were at risk of drowning or being lost at sea. But a study led by Morito Hayashi of London's Natural History Museum shows otherwise.
Hayashi's team observed hundreds of spiders from dozens of common species as they made a water landing in a controlled environment.
"Spiders actively adopt postures that allow them to use the wind direction to control their journey on water," Hayashi said in a news release. "They even drop silk and stop on the water surface when they want. This ability compensates for the risks of landing on water after the uncontrolled spider flights."
Back in 1832, Charles Darwin marveled over the "Aeronaut spiders" that kept dropping on the deck of the HMS Beagle, miles and miles from shore. "How inexplicable is the cause which induces these small insects, as it now appears in both hemispheres, to undertake their aerial excursions," he wrote.
The newly published study explains the mystery that Darwin posed. More generally, it helps explain how the web-spinning species was able to spread across wide bodies of water — and how they survived unfavorable circumstances like floods.
The research was published Friday in the journal BioMed Central Evolutionary Biology.