All creatures and practically everything have the urge to urinate. However, certain entities have a unique way of doing so, which involves expelling liquid at great velocity with the use of an anal stylus. This peculiar phenomenon is what a group of experts from the Georgia Institute of Technology have uncovered in their study on the defecation process of a leaf-jumping insect called the glassy-winged sharpshooter. Although it may appear niche, the knowledge they have gained could in the future offer practical applications such as rapidly ejecting water from delicate electronic devices.
The inquiry into the excretion process of the sharpshooter initiated from sheer inquisitiveness, as with many scientific explorations. Saad Bhamla, who works as an associate professor in chemical and biomolecular engineering, observed that one of these insects frequently produced a perfectly circular liquid droplet on its tail, which it would then propel at a remarkable velocity.
“We have limited knowledge regarding the fluid dynamics involved in excretion and its effects on an animal’s morphology, energetics, and behavior,” stated Bhamla. “Our objective was to explore any possible engineering or physics advancements adopted by this small insect to urinate in this manner.”
By studying the insect with high-speed video and microscopes, it was discovered that the sharpshooter has a specific anatomical structure that allows it to urinate with great precision and speed. This structure is called an “anal stylus” by Bhamla, who referred to it as the insect’s “butt flicker.”
Bhamla likens this characteristic to the flippers present in a pinball machine, which a proficient player employs to eject urine droplets at an astounding velocity. The flicker is capable of propelling the fluid at a speed exceeding that of the swiftest sports cars by over ten times.
According to Elio Challita, a bioengineering graduate student who collaborated with Bhamla, the team discovered that the insect had evolved a spring and lever similar to a catapult, allowing it to repeatedly launch droplets of urine at high speeds.
The research conducted by the team has been published in the current edition of the journal Nature Communications. During their experimentation, the researchers observed that the speed of the expelled droplets exceeded that of the stylus flicking them, indicating the possibility of superpropulsion – a phenomenon previously unobserved in natural systems.
Super propulsion occurs when an elastic projectile receives an increase in energy by synchronizing compression and launch timings. To illustrate this, think of a diver jumping off a springboard at precisely the right moment to obtain the maximum boost from the spring’s effect. In a similar manner, the sharpshooter’s stylus appears to compress the droplet before launching it, storing extra energy through surface tension in the liquid which then propels it forward at a higher velocity.
The scientists theorize that urination flicking is the most effective method for sharpshooters to digest the copious amounts of plant sap they consume daily in order to stay alive, which can be up to 300 times their own body weight.
Studying the restroom behaviors of sharpshooters may offer concrete advantages to humans as this insect is a significant pest causing extensive harm worth millions of dollars to crops, notably in vineyards and citrus orchards situated in California and Florida. With the anticipation of the species’ proliferation due to climate change, this fresh revelation could aid in monitoring its diffusion and facilitate valuable insights that assist in governing their procreation.
Nevertheless, valuable insights can be gained by engineers from the biology of sharpshooters, thereby enabling them to create innovative systems for expelling water from wearable technology. Miriam Ashley-Ross, a program director at the US National Science Foundation, which partly financed the research, stated that “What the sharpshooters are dealing with would be like us trying to fling away a beachball-sized globe of maple syrup that was stuck to our hand. The efficient method these tiny insects have evolved to solve the problem may lead to bio-inspired solutions for removing solvents in micro-manufacturing applications like electronics or shedding water rapidly from structurally complex surfaces.”
Taking a moment to contemplate a droplet of bug urine can lead to surprising discoveries. “This study supports the notion that science driven by curiosity is meaningful,” remarked Challita. “The revelation of the biological system’s ability for droplets to exhibit superpropulsion, along with its remarkable feats of physics that have far-reaching applications, makes the study all the more intriguing.”
