Insect that flings pee with a butt catapult is 1st known example of 'superpropulsion' in nature

Sharpshooters with glassy wings launch their poop in fast succession from butt catapults.

According to a new study, relatives of cicadas called sharpshooter insects can catapult urine droplets at extremely high speeds, providing the first documented instance of "superpropulsion" in nature.

In addition to enabling bugs to conserve energy while urinating, this newly found effect might also improve self-cleaning technology and soft robotic engines, according to researchers.

Researchers looked studied cousins of cicadas called glassy-winged sharpshooters (Homalodisca vitripennis) in the recent study. The xylem, a woody component of a plant that transports water and dissolved nutrients up from the roots as opposed to the phloem, which transports sugar down from the leaves, is where these insects, which are approximately half an inch (1.2 cm) long, feed on sap.

95% of the sharpshooter's diet consists of water, which is nutrient-poor. As a result, the bugs must continuously consume xylem sap to survive, and they can excrete up to 300 times their own weight each day. Humans, by contrast, urinate around one-fourth of their body weight each day.

The mechanics of feeding are well understood, but there is still much to learn about the physics of defecation, according to the experts. They concentrated on sharpshooters to examine if their little bodies had developed any ingenious strategies to deal with the continual "leafhopper rain" urination.

"I saw these insects peeing once and fell in love," said Saad Bhamla, a biophysicist at the Georgia Institute of Technology in Atlanta and the study's principal author, to Live Science.

The anal stylus, or "butt flicker," as Bhamla dubbed it, is a structure near the end of the sharpshooter that was examined by scientists using high-speed movies and microscopy. The stylus flexes downward to create room when the beetle squeezes out a droplet of urine when it is time to urinate. When the drop reaches the ideal size, the stylus bends even farther downward before launching the droplet with an acceleration of more than 40 g's, which is 10 times more than the acceleration of the quickest sports vehicles.

The stylus can move up to 0.75 feet per second (0.23 meters per second), according to the researchers. However, the propelled droplets travel at a rate of up to 1.05 feet per second (0.32 m/s), which is nearly 40% quicker.

The finding confirms the existence of the superpropulsion phenomenon, which was previously only seen in artificial environments. By matching its movements with those of its launchpad, similar to a diver timing their jump off a springboard, an elastic projectile using superpropulsion goes faster than its launchpad.

The researchers discovered that the droplets were squeezed by the stylus, storing energy in their surface tension immediately prior to launch to assist in catapulting them at high speeds. Because of how strongly the molecules in liquids cling to one another as opposed to something else, surface tension, which causes liquid surfaces to behave like flexible membranes, is what causes droplets of liquid to bead up.

According to research lead author Elio Challita, a biophysicist at the Georgia Institute of Technology, "often we overlook excretion because it's taboo or silly, but it's a critical biological function akin to feeding that has important energetic, ecological, and evolutionary implications." The first instance of superpropulsion in a living entity was discovered as a result of what began as a strange observation of an odd peeing mechanism.

The researchers utilized micro-CT scans to examine the architecture of the bugs and collect measurements from within the insects to understand why sharpshooters hurled pee droplets rather than spraying urine in jets. The scientists was able to use this information to compute the pressure and energy required for the insects to urinate, which showed that superpropulsion required four to eight times less energy than jets.

These discoveries might aid engineers in creating machines that need less energy to clean themselves. According to Challita, "water droplets frequently adhere to surfaces as a result of surface tension, which can be undesirable in a number of contexts, such as cleaning and preventing damage to electronics." Superpropulsion of droplets provides a method for ejecting droplets off surfaces by causing the surface to vibrate at the droplets' vibrational frequency.

Additionally, according to Challita, the findings could assist increase the effectiveness of the engines that propel soft, flexible robots. In conclusion, "we can discover some amazing things in our own backyards — we just have to look closely," Bhamla added.