As if things couldn’t get worse for those suffering from arachnophobia. First we had the redback spider taking down a snake, then the massive web discovered in Texas. Now, researchers have found that not only can spiders cartwheel and sail, they can also “fly”. Steering themselves with their forearms, the large spiders of the Selenops genus can skillfully maneuver themselves mid-flight when falling from the canopy to land on a tree trunk 25 meters (82 ft) below.
The new study, published this week in the Journal of the Royal Society Interface, documents this unexpected finding, as spiders have no history of flight. How this gliding behavior came to occur remains a bit of a mystery, though it could be because tree trunks offer relative safety for the spiders compared with the forest floor, where they might get snapped up by other hungry creatures.
The flatties show quite an amazing degree of control as they fall from the canopy. Guardian Science and Tech/YouTube.
The researchers made their discovery in a rather unconventional way. For years they’ve been looking for insects that show a knack for gliding, and they test suspects in a fairly simple manner – by dropping them from a height. These experiments have allowed them to show how many species of insects can make controlled gliding descents, from praying mantises to grasshoppers, and they also found how many species of tree-climbing ants have also evolved this ability. But they then turned their focus onto the bigger creepy crawlies, settling on the large flat spiders imaginatively known as “flatties.”
After coating specimens with a fluorescent powder, researchers tipped them out of a cup while up in the canopy of a forest and monitored their descent. Out of the 59 flatties tested, 93% of them were successfully able to right themselves and then maneuver through the forest to a trunk without the use of anything else, such as silk. The arachnids manage this feat in a way not dissimilar to skydivers, by tucking their heads in and then using their limbs to direct their travel. They also reckon that the spiders' flat bodies also help them to glide. So if you're ever trekking through the forests of South America, you might want to keep an eye out for low-flying spiders.
Main image credit: Mark Yokoyama/Flickr (CC BY-NC-ND 2.0)