Leg over leg, a furry brownish—black spider pulls on a single silk thread, tightening the frame of its web. It pulls and pulls and it waits. Minutes pass, sometimes hours. Then, when an unsuspecting insect flies by, the spider releases the thread, springing itself and its satellite dis—shaped web toward its prey. All of this happens in the blink of an eye.
Those eye—watering numbers led Georgia Tech chemical engineer Saad Bhamla to wonder：How are these tiny spidersachieving such fast movements？Then he started to investigate. He checked the literature and found only a few papers. The papers were decades old and only described the slingshot motion, not the speeds or G—forces the spiders experienced. So Bhamla enlisted the help of his assistant, Symone Alexander, and together they "went out hunting for spiders in the Amazon rainforest, " Alexander says.
After locating one of the spiders, which measures roughly 2 millimeters in length, the researchers would set up portable high —speed cameras with special lenses and record its motions. Then, either Alexander or Bhamla would snap their fingers (打响指) to get the spider to launch itself through the air. Only later did the pair learn that a human finger-snap closely matches the frequency of a buzzing mosquito—and that seemed to be the only frequency that set the spiders' spring off. "It's just amazing that we can snap our fingers and get this magical thing, "Bh am la says. Analyzing the footage, Alexander and Bhamla could watch exactly how the spider adjusted itself on the tension line at the front of its web. "The speed and acceleration of this spider are impressive, but so is the fact that, unlike most web-building spiders, it's actively hunting, "Bhamla says. "It's changed the function of its web, " he says. "Instead of waiting for something to bump into it, the spider is going after things. . . actually catching flying insects in midair. "
