freefall, and an order of magnitude greater
than that of a sprinting cheetah.
Those eye-watering numbers led
Georgia Tech chemical engineer Saad
Bhamla to wonder: How the heck are
these tiny spiders achieving such fast
movements? Bhamla’s lab is “obsessed
with ultra-fast motions in biology,” he
says, so when he spotted one of these
spiders flying past his face a few years
ago while he was hiking through the
Peruvian rainforest, he knew he had to
investigate. He checked the literature
and found only a few papers on Therid-
iosomatidae, the arachnid family com-
prising spider species that use their webs
as slingshots. The papers were decadesold and only described the slingshot
motion, not the speeds or g-forces
the spiders experienced. So Bhamla
enlisted the help of his postdoc, Symone
Alexander, and together they “went out
hunting for spiders in the Amazon rain-
forest,” Alexander says.
After locating one of the spiders,
which measure roughly 2 millimeters
in length, the researchers would set up
portable high-speed cameras with mag-
nifying lenses to zoom in on and record
their motions. Then, either Alexander
or Bhamla would snap their fingers to
get the spider to catapult itself through
the air. Only later did the pair learn that
a human finger-snap closely matchesthe frequency of a buzzing mosquito—
and that seemed to be the only fre-
quency that set the spiders’ spring off.
“It’s just amazing that we can snap our
fingers and get this magical thing,”
Bhamla says.
Analyzing the footage, Alexander
and Bhamla could watch exactly how
the spiders oriented themselves on the
tension line at the front of their webs.The spider can usually sling-
shot itself several times
before the web is destroyed.ANDRZEJ KRAUZE
11.2020 | THE SCIENTIST 17