for National Geographic News
With Spider-Man, the world's most famous web-slinger returning to the movie screens today, spiders everywhere may be readying their webs for a bit more attention. But how do our red-and-blue hero's capabilities compare with the superpowers of real spiders?
Spiders aren't swinging their way through the skyline or facing up to crazed criminals like Doc Ock, the villain in Spider-Man 2. But they've got the wherewithal to survive in a range of environments that gives them their own extraordinary edge.
Many species of jumping spider, found all over the world, can bound as much as 50 times their body length. Right now, U.S. long jumper Mike Powell holds the world's record with a jump of 8.95 meters (29 feet, 4.5 inches). If the six-foot-two (1.9-meter) Powell had a jumping spider's hopping capability, he might be able to leap 300 feet (90 meters).
Jumping spiders use these fantastic leaps to snatch unsuspecting insects. "They hunt down prey, and then they'll pounce on it," said Andrew Martin, from the Institute of Technical Zoology and Bionics at the University of Applied Sciences in Bremen, Germany.
How Spiders Walk on Ceilings
Some spiders have another seeming superpower: an ability to adhere to sheer surfaces, even when upside down. To find out how they do this, Martin and colleagues studied the foot of a jumping spider, Evarcha arcuata, through an atomic force microscope.
The spider's foot is covered with hairs, or setae, that branch into ever smaller hairs, or setules. Through their powerful microscope, the team studied the forces acting on a single seta. They calculated that the grip of the jumping spider is so strong that it could hold 170 times the spider's own body weight before coming unstuck. That would be the same, Martin said, as Spider-Man lugging 170 people from danger while clinging to a building with his fingers and toes.
What's at work in real spiders are van der Waals forces, caused by moving electrons that create hot spots of attraction between nearby molecules. With these miniscule charges acting on the 600,000-plus setules in each furry seta, a spider can hang upside down on a leaf or a wall with ease.
The unusual thing, Martin said, is that the spider's clinging ability resembles that of a gecko more than that of an insecteven though eight-legged spiders are much more closely related to six-legged insects than to lizards. "From a biological point of view, that was pretty astonishing," he said.
The team, which published its findings this spring, hopes the secret of the spider's stickiness can be adapted for human usessticky notes, boots for astronauts, even gloves for soccer goalies.
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