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In the Amazon rainforests of Peru, a tiny slingshot spider has adapted a less passive form of hunting, using its web as a slingshot to trap unsuspecting flies and mosquitos. Blown away by the strength exhibited by a spider that's around 1 millimeter in size, researchers decided to take a closer look at the mechanics of this unusual feeding strategy to find out how something so small could spring a web with an acceleration 100 times faster than a cheetah. Their findings were published in the journal Current Biology.
Carried out by a team from the Georgia Institute of Technology, the research is the first kinematic study into how these spiders can store enough energy to fling their webs with such ferocity. Their slingshots accelerate at approximately 1,300 meters per second (4,260 feet per second), subjecting the spider to forces of approximately 130 Gs. For context, that’s more than 10 times the force fighter pilots can tolerate before blacking out.
"Unlike frogs, crickets, or grasshoppers, the slingshot spider is not relying on its muscles to jump really quickly," said Saad Bhamla, an assistant professor at Georgia Tech's School of Chemical and Biomolecular Engineering who studies nature’s speedy elite, in a statement. "When it weaves a new web every night, the spider creates a complex, three-dimensional spring. If you compare this natural silk spring to carbon nanotubes or other human-made materials in terms of power density or energy density, it is orders of magnitude more powerful."
As part of the genus Theridiosomatid, slingshot spiders catch their prey using their conical webs as tools. The web has a tension line running through the center, which the tiny spider pulls using its rear legs until it's taught. When a meal is in reach, the spider catapults its web quickly, wrapping the prey in silk.
What’s so hard to understand about this is how such a small spider has enough energy to hold the web in place as it waits for food. Bhamla and colleagues estimated that stretching the web requires at least 200 dynes, a tremendous amount of energy for a tiny spider to generate.
"Generating 200 dynes would produce tremendous forces on the tiny legs of the spider," Bhamla said. "If the reward is a mosquito at the end of three hours, is that worth it? We think the spider must be using some kind of trick to lock its muscles like a latch, so it doesn't need to consume energy while waiting for hours."
The researchers' work has been cut short due to the coronavirus, but when they are able to start again they hope to get back to the rainforest and find out more about how these tiny animals maintain such strength for so long. They hope that understanding how the web’s silk stores energy could lead to novel power sources for tiny robots and other devices, and lead to new applications for super-strong silk.
