This summer, if you're walking under trees filled with the buzzing songs of cicadas, you might want to carry an umbrella. Not for rain, but for cicada pee.
Unlike most small insects that politely excrete droplets, cicadas dramatically expel jets of urine, according to new research from Georgia Tech published in PNAS. As assistant professor Saad Bhamla explains, "Cicadas are the smallest animal to create high-speed jets, so they can potentially inform applications in making jets in tiny robots/nozzles."
The research team had a lucky break observing the elusive cicadas in action while doing fieldwork in Peru. As Bhamla notes, "seeing a cicada pee is an event." I knew entomologists led exciting lives, but I had no idea it incuded thrills of this magnitude.
From Georgia Institute of Technology:
This moment of observation was enough to disprove two main insect pee paradigms. First, cicadas eat xylem sap, and most xylem feeders only pee in droplets because it uses less energy to excrete the sap. Cicadas, however, are such voracious eaters that individually flicking away each drop of pee would be too taxing and would not extract enough nutrients from the sap.
"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 Elio Challita, a former Ph.D. student in Bhamla's lab and current postdoctoral researcher at Harvard University.
Second, smaller animals are expected to pee in droplets because their orifice is too tiny to emit anything thicker. Because of cicadas' larger size — with wingspans that can rival a small hummingbird's — they use less energy to expel pee in jets.
"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," Challita said.
Cicada pee streams could inspire advances in fields like soft robotics, manufacturing, and drug delivery. "Biology and the diversity across forms of life have the potential to drive advances in fields from healthcare to manufacturing," said Miriam Ashley-Ross, program director at the U.S. National Science Foundation.
See also: Parasite fills cicadas with amphetamines and mind-altering drugs
