Insect Gears

Insect Gears Cog wheels connecting the hind legs of the planthopper.
Photo Credit: Burrows/Sutton

Some insects’ legs have gears that look and function like the classic man-made invention.


Insects that get in gear. I'm Bob Hirshon and this is Science Update.

Humans have been building gears into machines since ancient times. But insects called planthoppers may have developed gears long before us.

British researchers Malcolm Burrows and Gregory Sutton found that immature planthoppers, or nymphs, have toothed gears built into their hind legs. Burrows, a neurobiologist at the University of Cambridge, says the gears look and function just like the man-made kind.

There’s nothing like it being reported in animals at all. It’s never been thought that it’s something that animals ever use. So this is quite a surprising finding.

The gears synchronize the hind legs with remarkable accuracy, on the scale of microseconds. That helps the nymphs make quick, powerful jumps. Burrows was struck by how closely humans unintentionally copied nature in the invention of gears. I’m Bob Hirshon for AAAS, the Science Society.

Making Sense of the Research

Scientists and engineers often look to nature for inspiration. That's because living things have, through millions of years of natural selection, gradually adapted to their environments in ways that are often potentially useful to human technologies. In other words, we like to try and steal Nature's secrets.

In this case, humans may have stolen a secret without even knowing it. Gears—toothed, interlocking rings that turn together—have been used in machines going back to ancient China and Greece, and remain an essential building block of machines today. Now, these researchers have found the same mechanism in the legs of an insect.

The planthopper nymph's natural gears are found on its hind legs. The gears coordinate the legs so that when the nymph jumps, its legs push off the surface at almost exactly the same time. The researchers found that the gears coordinate the legs even more accurately than its brain could, because they cut out the (incredibly short!) time that it takes for nerve signals to travel from the brain to the legs.

Interestingly, adult planthoppers' legs don't have gears. In the juvenile stage, planthopper nymphs molt, or grow a new exoskeleton, every few days, and with each molt comes a brand-new set of gears. But when nymphs molt for the last time and become adults, their final exoskeleton lacks gears. That may be because the gears' teeth are too small and delicate to last more than a few days without breaking. 

Although humans probably can't learn anything more about gears from these insects, it shows us that Nature, too, figured out that gears can be useful tools—probably long before we did.

Now try and answer these questions:

  1. How do the planthopper nymphs use their gears?
  2. Why is this finding significant?
  3. What does it tell us that the insect gears are so similar to gears that humans have designed?
You may want to check out these related resources:

For examples of engineers trying to deliberately copy nature, see the Science Updates Super Water Repellent, Sea Sponge Fibers, and Ultra-White Beetle.

Going Further

For Educators

For examples of engineers trying to deliberately copy nature, see the Science Update lessons Super Water RepellentSea Sponge Fibers, and Ultra-White Beetle.

In the Science NetLinks Lesson Organisms in Motion: Practical Applications for Biological Research, students explore the ways in which a scientist is applying research on animal locomotion for practical human uses, examine the locomotion of microscopic protists, and propose potential practical applications of their observations.

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