Physics: Sharpshooter insects catapult pee droplets to save energy

Sharpshooter insects use droplet superpropulsion to eliminate high volumes of their waste, up to 300 times their own body weight per day, a Nature Communications paper reports. This mechanism allows sharpshooters to catapult droplets, forming ‘leafhopper rain’ as a strategy to conserve energy, the findings suggest.

Millimeter-scale sharpshooter insects have a diet that is 95% water and poor in nutritional components. They eliminate up to 300 times their body weight per day, compared to about 2.5% of body weight per day in humans. To survive on this diet, these insects use large muscles and an efficient digestive system to extract and filter large volumes of plant fluid.

Saad Bhamla and colleagues found that sharpshooter insects form pee droplets through superpropulsion as a strategy to conserve energy compared to other mechanisms of waste disposal, such as producing a jet stream, as seen in Cicadidae. Superpropulsion is a phenomenon where an oscillating surface can propel a drop of liquid upward at a speed higher than that of the oscillating surface. In a series of experiments the authors demonstrate that these insects temporally tune the frequency of their anal stylus to the frequency of their pee droplets as a single-shot mechanism.

The findings may inform insect-inspired engineering designs of energy-efficient self-cleaning structures and soft robotic engines, the authors suggest.