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.
