Sailing Spiders?! Young Arachnids Eschew Flight For the Sea

Arachnophobics beware: the deepest moat between you and your eight-legged nemeses will not keep you safe. Experts have recently determined that some species of spider can travel across water, using their bodies like sail-boats in order to reach new places where they can thrive and terrify.

If you're familiar with Charlotte's Web than you already know that many spiders can fly, at least when they're young. Tiny arachnids will take to the air in a process called 'ballooning,' casting kite-like silk structures to catch the wind and carry them to new destinations. Experts have estimated that ballooning spiders can travel up to 20 miles a day (~30km) under the right conditions, allowing young to quickly colonize new habitats and discover new resources.

However, there has always been one problem with this strategy (aside from spiders in your hair).

"Given that spiders are terrestrial, and that they do not have control over where they will travel when ballooning, how could evolution allow such risky behavior to be maintained?" Morito Hayashi from the Natural History Museum, London, UK, asked in a recent statement, noting that even Charles Darwin wondered about this when he encountered flying spiderlings during the historic voyage of the Beagle.

"We've now found that spiders actively adopt postures that allow them to use the wind direction to control their journey on water," he added. "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." (Scroll to read on...)

Morito only determined this after observing the behavior of a whopping 325 adult spiders belonging to 21 common species, as found on protected islands around Nottinghamshire, UK.

Aside from field observations, the researcher exposed these collected spiders to trays of water and pump-generated air - simulating the same travel conditions they'd encounter when ballooning.

The result, as detailed in the journal BMC Evolutionary Biology, showed that sea-stranded spiders could often adapt elaborate postures, lifting their spindly legs to create what essentially functioned as sails. This allowed them to maintain a steady course even on turbulent waters, increasing the chances that they would find new land despite their unfortunate fall from the sky.

Interestingly, Morito and his colleagues found that the spiders most adapted for air travel were also the best 'sailors.'

"Being able to cope with water effectively 'joins the dots' as far as the spider is concerned," study co-author Sara Goodacre of the University of Nottingham added. "If landing on water poses no problem then in a week or two they could be a long way away from where they started."

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