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Cicada urination defies what scientists thought was possible

The serene buzz of cicadas often heralds the arrival of summer, yet it’s their unique method of urination, rather than their iconic sound, that has piqued the interest of researchers at Georgia Institute of Technology

Unlike the typical droplets excreted by many insects, cicadas expel powerful jets of urine. This phenomenon has intrigued study senior author Professor Saad Bhamla and his team for its uncommon fluid dynamics.

Observing cicada urination 

Despite the prevalence of cicadas and their unmistakable chorus, observing them in action is challenging due to their penchant for remaining hidden within the foliage. 

The team’s breakthrough came during fieldwork in Peru, where they observed numerous cicadas engaging in their distinctive urination process directly, a rarity that had previously been limited to online video observations.

Jetting urine for nutrient extraction 

This direct observation debunked two longstanding beliefs about insect urination. Traditionally, it was thought that insects feeding on xylem sap, such as cicadas, would naturally excrete in droplets to conserve energy, as xylem sap is not nutrient-rich. 

Cicadas, however, consume sap so voraciously that jetting urine becomes a more efficient method for nutrient extraction. 

New insights on insect urination 

“The assumption was that if an insect transitions from droplet formation into a jet, it will require more energy because the insect would have to inject more speed,” said study lead author Elio Challita, a former Ph.D. student in Bhamla’s lab and now a postdoctoral researcher at Harvard University.

“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. But a larger animal can rely on gravity and inertial forces to pee,” explained Challita.

However, the recent cicada study challenges the notion that smaller animals are constrained to droplet urination due to the size of their orifices, which would supposedly make jetting biologically expensive. 

Broader understanding of fluid dynamics 

Cicadas, with their relatively large size compared to other insects, leverage their physical dimensions to minimize energy expenditure while expelling urine in jets.

This insight into cicada urination provides a broader understanding of fluid dynamics across the animal kingdom, from minuscule insects to large mammals. Professor Bhamla’s group has extensively studied fluid ejection in various species, uncovering applications ranging from soft robotics to drug delivery, based on the mechanics of fluid expulsion observed in nature.

Implications of cicada urination 

Cicadas, being among the smallest creatures capable of generating high-speed fluid jets, offer a model for developing efficient jet mechanisms in microscale applications like robotics and spray nozzles. 

Furthermore, with cicada populations reaching into the trillions, the ecological ramifications of their urination habits remain a largely unexplored area with potential implications for bio-monitoring and environmental science.

Excretory patterns of animals

The research transcends mere academic curiosity, providing a window into the excretory patterns of life forms as varied as cicadas and elephants. 

“Our research has mapped the excretory patterns of animals, spanning eight orders of scale from tiny cicadas to massive elephants,” said Bhamla.

“We’ve identified the fundamental constraints and forces that dictate these processes, offering a new lens through which to understand the principles of excretion, a critical function of all living systems.” 

“This work not only deepens our comprehension of biological functions but also paves the way for unifying the underlying principles that govern life’s essential processes.”


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