These insects sling pee
with a tiny ‘catapult’
Some sap-sucking insects can “make it
rain,” flinging droplets of pee while feeding on plant juices. Now scientists have
explained how insects known as sharpshooters create the spray using a tiny
catapult-like structure on their rear that
propels the waste at extreme accelerations.
Engineer Saad Bhamla of Georgia
Tech in Atlanta and colleagues recorded
high-speed video of two species, the blue-green sharpshooter (three images at top
left) and the glassy-winged sharpshooter
(images at bottom left and below). Those
videos showed that a tiny barb called a
stylus at an insect’s rear end acts like a
spring. Once a drop collects on this structure, the “spring” releases, and the drop
flies off as if hurled from a catapult.
What’s more, tiny hairs at the end of
the stylus (seen in the bottom images)
increase its flinging power, Bhamla and
colleagues suggest, much like the sling at
the end of certain types of catapults.
As a result, the stylus launches liquid
waste with a maximum acceleration about
20 times that of Earth’s gravity, the
scientists report January 5 in Tampa, Fla.,
at the annual meeting of the Society for
Integrative and Comparative Biology.
A tree infested with sharpshooters
exudes a steady pitter-patter of pee,
which can dampen unsuspecting pass-ersby. “It’s crazy just to look at,” Bhamla
says. It’s not clear why the insects fling
their pee. Perhaps they avoid a bath in a
fluid that could attract predators, he says.
— Emily Conover