London - Spiders are able to travel across water using their legs as sails and silk as an anchor, scientists have found.
The revelations – bound to horrify arachnophobes – help to explain how the creatures can travel vast distances, even over seas.
And it solves the puzzle of how they survive if they accidentally land on water, as it is already known that they use strands of silk to catch the wind and “fly” up to 18 miles a day.
Researchers from the University of Nottingham collected 325 spiders from small islands in English nature reserves. The arachnids came from the linyphiid and tetragnathid families, which together represent around 13 percent of all known species. They were then blown across trays of water that were turbulent, still, fresh and salt.
Many lifted their legs to create “sails”, while dropping a length of silk slowed them down or fixed them to a rock. Some even used their abdomens to catch the breeze.
The findings could explain why spiders have been known to traverse long distances, often turning up on islands a considerable distance from the nearest shore. It could also increase their chances of survival after heavy rains or floods.
Morito Hayashi from the Natural History Museum said: “Even Charles Darwin noted that spiders kept dropping on the Beagle miles away from the sea shore.
“But given that spiders are terrestrial, and that they do not have control where they will travel when ballooning [flying], how could evolution allow such risky behaviour?
“We’ve now found that spiders actively adopt postures that allow them to use the wind direction to control their journey on water. They even drop silk and stop on the water surface when they want.”
He added that the ability to sail compensates for the risk of uncontrolled flights. Spiders which were particularly good at flying were also found to be the best sailors.
Study co-author Sara Goodacre said: “[Spiders] can move from one land mass to another, and potentially across huge spatial scales through the air. If landing on water poses no problem then in a week or two they could be a long way from where they started.”
The study is published in the journal BMC Evolutionary Biology.
Daily Mail