Nature
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Cicada season is coming up soon, and you’d better make sure you grab your raincoat if you’re planning on heading outside. Why, we hear you ask? Not because of April showers, it turns out, but because you might just get hit by a jet stream of cicada pee – and this unusual trait has helped researchers disprove widespread beliefs about how insects urinate.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Researchers have long been baffled by the way that cicadas urinate and not just because it’s a pretty bizarre sight to behold. It goes against two insect pee paradigms and a team from Georgia Tech set to figuring out why.
The first widely accepted theory involves how cicadas eat. Cicadas feed on sap from a plant’s xylem (the tissue that carries water through a plant) and most insects that do the same pee in droplets in order to save energy.
For cicadas, however, the researchers discovered that peeing in droplets would actually be less energy efficient. When you’re a beefed-up insect like a cicada, you have to eat a lot, and that means peeing a lot too – flicking away that many droplets would be far too taxing. After all, they need as much energy as they can muster to make incredibly irritating levels of noise.
We had to see a cicada peeing and now you do too.
The second paradigm is that smaller animals also normally pee in droplets, because they tend to have smaller orifices, which aren’t energy conducive to shooting out a stream of pee at high speeds.
“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. This is due to surface tension and viscous forces,” explained study author Elio Challita in a statement.
But because cicadas are on the larger side when it comes to insects, the researchers found that they actually use less energy to pee in jets. “A larger animal can rely on gravity and inertial forces to pee,” said Challita.
Since cicadas appear to be the smallest animal that urinates in such a way, the researchers believe that studying how they wee could have real-world applications, potentially informing the development of tiny robots and small nozzles.
“This work shows that even the way in which organisms get rid of waste can provide new insights into fluid dynamics that spur innovation in soft robotics and ways to handle fluid at small scales in all manner of manufacturing,” said Miriam Ashley-Ross, program director at the U.S. National Science Foundation, which provided funding for the research.
Who knew we could learn so much from high-speed insect piss?
The study is published in PNAS.
