Researchers reveal the fluid dynamics behind cicadas’ ‘unique’ urination

16 Mar 2024 Michael Banks

This year promises to be a bumper one for cicadas, given that 2024 marks the first time in more than 200 years that two broods belonging to two species will emerge simultaneously.

Now, researchers at Georgia Institute of Technology in the US say we might have more to worry about than just the cacophony the insects are famous for.

They have studied cicadas’ “unique” ability to produce jets of urination from their tiny bodies.

Most insects urinate via droplets because it takes less energy, and their orifices are too small to do anything else.

Cicadas, however, are such voracious eaters of tree sap that individually flicking away each drop would be too taxing and result in being unable to extract enough nutrients.

They pee via short jets to get around this problem (see video above).

“Previously, it was understood that if a small animal wants to eject jets of water, then this becomes a bit challenging because the animal expends more energy to force the fluid’s exit at a higher speed,” notes Elio Challita, currently based at Harvard University. “This is due to surface tension and viscous forces. However, a larger animal can rely on gravity and inertial forces to pee. ”

Due to the cicadas’ larger size, they use less energy to expel a jet, and indeed, it turns out that cicadas are the most miniature animals to create such high-speed jets.

The team thinks a greater understanding of cicada's urination could help design better nozzles and robots.

And with a double brood emerging this year, it could be a noisy and wet summer.

Michael Banks is the news editor of Physics World magazine.

FROM PHYSICSWORLD.COM     30/3/2024