Nature

13
Sep

This Insect Jumps Using Built-In Gears

Biomimicry—the use of nature to inspire design—is widely used by cutting-edge technologists to design everything from bullet train noses, new X-ray machines, and lighter and safer cars. But let’s take a moment to flip that idea on its head. Are there things we thought humans invented that have been later discovered in nature?

As a matter of fact, yes. Nymphs of a common insect found in Britain—Issus coeleoptratus, a species of planthopper—has what were presumably a very human creation—gears. While working at the University of Cambridge, Greg Sutton noticed a strange mechanism on the insect’s back legs. Here’s Adam Cole reporting for NPR’s Morning Edition:

There was a tiny row of bumps on the inside of each leg where it met the insect’s body. The bumps looked just like the teeth of gears. And when the planthopper jumped, they acted like gears too — as teeth meshed, the legs turned in synchrony. Sutton says his finding, published this week in Science, is the first mechanical gear system ever observed in nature.

insect-gears
Trochanters found in the nymph stage of Issus coeleoptratus

The small bumps—called trochanters—are incredibly well suited to the planthopper, which springs away from danger in the blink of an eye. Sutton filmed the bugs hopping with a high-speed camera and noticed that both leaping legs moved almost simultaneously—the difference between the two was as short as 30 millionths of a second. That’s much shorter than the time it takes for a neuron to execute even the smallest, most rudimentary task. The synchrony propels the insect faster, farther, and straighter.

Ed Yong, writing for Not Exactly Rocket Science, has more background on Sutton’s research:

The planthopper nymphs lose them when they become adults. But the adults don’t shoot off in uncoordinated spins—if anything, they’re better jumpers than the youngsters. Their hind trochanters make much closer contact with each other, and Sutton thinks that the friction between them helps to keep them in time. “We’re kind of sure about that, but not entirely sure,” he says.

Issus coeleoptratus‘s gears work similarly to their human-designed counterparts, but they have a leg up at smaller scales. Sutton—a mechanical engineer—thinks the trochanters could help us build more efficient machines:

Modern machines, such as 3-D printers, could easily create gears with these shark-fin teeth. Sutton is really excited by the prospect, and suspects that they may perform better in very small machines. “Modern machinery often doesn’t work at very small scales,” he says. “Friction doesn’t matter so much when you have two big gears next to each other but when you get small, friction starts killing you.”

The planthoppers might help to solve that problem. “We’re still being impressed and shocked by what we find in the back garden,” says Sutton.

For more bioinspired technologies, watch “Making Stuff Wilder”, airing October 23 at 9/8 central on PBS.