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Beetle Filmed Walking Underwater On The Underside Of A Puddle's Surface


Rachael Funnell

Social Editor and Staff Writer

clockJul 1 2021, 16:59 UTC
Beetle Filmed Walking Upside-Down Underwater Using Puddle Surface's Underside As Floor

It's exactly as bizarre as it sounds. Image courtesy of Dr John Gould

The longer you look at nature, the weirder it gets. From self-decapitating sea slugs who can grow a new body to lacewings who can take out six termites with a single fart, there’s some pretty freaky stuff going on out there. Spending a lot of time amidst the action, field researchers are often uniquely placed to spot bizarre and previously unknown to science behaviors, though waiting for them to happen can be a little perilous.

For Dr John Gould and Dr Jose Valdez, however, the wait paid off. While searching for tadpoles in pools in the Watagan Mountains, Australia, they spotted something unusual moving through the water. About the size of a fingernail, a beetle was scurrying along the water’s surface. However, instead of using the upside – that is, where the air is – it was scurrying along the water’s surface while itself underwater. A baffling concept, we’ll agree, but fortunately, the two snapped a video of the animal as well as publishing their findings in the journal Ethology.



The footage constitutes the first time this behavior has been captured in any detail being practiced by a beetle. So, who was this wonder wanderer?

“Since there are many similarly looking beetles that live in water and the fact that it was upside down, made this beetle very difficult to identify,” said Valdez to IFLScience. “However, we received some help from Martin Fikáček, an entomologist specializing in beetles, which later helped to identify it as belonging to the aquatic beetle family Hydrophilidae, otherwise known as a water scavenger beetle.”


A beetle specialist indeed, Fikáček’s own paper recently went live detailing a new genus and species of beetle found hidden within the fossilized dung of a reptile that lived 230 million years ago.

Scavenger beetles spend almost their entire lives underwater if they can help it, only surfacing for oxygen. Their unique morphology means oxygen can be trapped in their body hairs to keep them oxygenated underwater for long, while others have been seen carrying bubbles with them for the same purpose. One such bubble can be seen being held by the beetle in the video, and Gould and Valdez suspect that it may play a role in keeping the insect stuck to the underside of the water’s surface.

Being such a novel observation, there are many questions about the behavior that remain unanswered. How the action is even possible is something of a puzzle itself, as these beetles have water-repellent bodies. It would stand to reason, then, that when affixed to the water surface’s underside the insect would be flipped surface-side by buoyancy. But this was not the case, the researchers urge, as not only could the beetle walk in this way but it could sit at rest on the water surface’s underside, too.


“That means it can remain at the water's surface without expending any energy,” said Gould to IFLScience. “This is in contrast to large animals that move across the water's surface, such as lizards, which need to keep running in order not to sink through the surface.  This ability could also mean that it could avert predation by minimising the amount of noise it makes while remaining still.”

It seems we have some ways to go in understanding the hows and whys behind this strange behavior, but Valdez is satisfied that unraveling the puzzle will prove an insightful quest for the pair.

“That is why observations like this are so important besides the wow factor,” he said. “It can lead to further questions down the road and a better understanding of the natural world around us. All we need is a curious mind and a discerning eye.”




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