New Zealand

Sharpshooter a wee champion at sending urine on its way

Mon, Mar 6

The sharpshooter insect, sweet and unassuming, has a skill unlike any other. It can fire droplets of pee using a little catapult built into its bum.

By Asia Martusia King of

Not only that, but sharpshooters catapult up to 300 times their own body weight of wee per day.

Researchers from the Georgia Institute of Technology, who have been spying on glassy-winged sharpshooters urinating, refer to this fancy phenomenon as superpropulsion.

It is a phenomenon which has not been observed in any other living creature.

Superpropulsion occurs when an object shoots out of a moving surface (such as a wiggly insect bottom) faster than the thing that propelled it.

The insect's urine spouts from a pointy tube on the backside known as an 'anal stylus'. The anal stylus flicks away at the perfect moment, sending pee blobs flying into the air, resulting in its eponymous sharp-shooting accuracy.

The sharpshooter isn't just pissing about — there's a biological reason for its unique skill.

"It helps the sharpshooters conserve energy," Saad Bhamla, who worked on the project, said.

At its 1mm size, smaller than a human pinky, excretion is challenging due to surface tension. Too little to produce a hearty stream, the sharpshooter instead fires off a series of blobs.

Why the need to conserve energy? Sharpshooters feed mostly on xylem, a type of sap which is almost entirely made up of water, not unlike celery. To survive on this diet, the insects use large muscles and an efficient digestive system to extract and filter massive volumes of plant fluid.

Because of xylem's low nutrients, Saad explained, the superpropulsion principle helps them to eliminate astronomical amounts of urine.

"Since [sharpshooters] do this often and in huge multitudes, it could also prevent them from peeing on each other," Saad said.

Animals, like most humans, do not like being peed on. "Waste accumulation in one place could also attract predators."

Saad has two favourite moments from his studies: "When I first saw sharpshooters pee, I fell in love," he said.

This was closely followed by the moment when fellow researcher Elio Challita proved that they were doing superpropulsion. "That just blew my mind."

The team is fiercely passionate and their effect is contagious.

"Kids love to hear about insect pee. Adults are amazed that there is so much rich physics and engineering."

Saad's paper suggested that by looking at sharpshooter butts, engineers might get some inspiration for energy-efficient robot designs.

"We can discover amazing things even in our backyard," he said. "We just have to look closely."