Bugs and beetles can’t hold their breath underwater like we do. But some aquatic insects can spend their whole adult lives underwater. How do they do it? Meet nature’s Scuba divers. They carry their air with them—in some cases, for a lifetime.
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--- How do some insects breathe underwater?
Air-breathing aquatic bugs and beetles don’t hold their breath the way sea mammals do, nor do they have gills like fish.
So how do they do it? The answer lies in their small size. Insect scuba strategies hinge on a property of water that relative giants like us usually overlook: surface tension.
People first crossed the line between land and sea to become scuba divers more than 70 years ago, when Jacques Cousteau pioneered the Aqua-Lung in Nazi-occupied France.
But some species of aquatic insects have been doing it for millions of years.
“Water beetles have been breathing underwater since before the dinosaurs existed,” said Crystal Maier, an entomologist at The Field Museum in Chicago. “It has evolved at least 10 times across the insect tree of life.”
--- What is surface tension?
Surface tension is the property of any liquid that describes how its particles stick together. In the case of water, surface tension is especially strong, enough to form a kind of film where it meets the air, whether at the surface or in a bubble.
The film is so strong, in fact, that a paper clip, which should sink because of its density, will float.
Surface tension is a delicate force, vulnerable to changes temperature, turbulence or the introduction of contaminants, like soap. A sudden drop in surface tension can drown a whole insect community in an instant.
Though it might not seem to affect our world to the same degree, surface tension is active all around us. It allows raindrops to form, trees to bring water to their leaves and ice to float. So in a sense, we too live on a thin boundary, ruled by the same subtle properties of water.
--- How do beetles use surface tension to breathe underwater?
If you’re a bug the size of a paperclip, in other words, surface tension makes a difference. Harnessing it, some aquatic beetles carry the oxygen they need underwater in the form of a temporary bubble, sort of like a natural scuba tank. Others encase themselves in a layer of air and draw oxygen from it their whole lives.
“It’s a pretty successful group of insects. They’re on every continent, except Antarctica,” said Cheryl Barr, collection manger emeritus at the Essig Museum of Entomology at UC Berkeley.
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