18 THE SCIENTIST | the-scientist.com
Facing away from the web, the spider
grips its silk net with its four back legs
and pulls itself up the tension line with
its four front legs, bundling it up in two
front appendages called pedipalps as
it goes. On sensing the sounds of prey
nearby —most likely via its web, which
appears to act like a small antenna—
the spider releases the tension line.
Although researchers had previously
assumed it let go of the silk thread
altogether, Alexander and Bhamla’s
videos show that the spider in fact only
releases some of the line while keeping
hold of a part of it with its pedipalps,
making it easier to reset its sling-
shot to trap its next victim (Curr Biol,
30:R928–29, 2020). Again and again,
the spider captures an insect, wraps it
in silk for later, then “comes right back
to that tension line and bundles it up
again. That allows it to reset and reload
pretty quickly,” Alexander says. The spi-
der can usually slingshot itself several
times before the web is destroyed.
The speeds and accelerations of this
spider are impressive, but so is the fact
that, unlike most web-building spiders,
it’s actively hunting, Bhamla says. “It’s
changed the function of its web,” he
says. “Instead of waiting for something
to collide with it, the spider is going
after things... actually catching flying
insects in midair.”
To see the video of this little spider
pull on its line, load its web, sense its
prey, and then fly through the air to trap
it is humbling, says Sheila Patek, a biolo-
gist at Duke University who studies tiny
spring mechanisms across the natural
world but was not involved in this work.SETTING UP: Chemical engineer Saad Bhamla
(left), postdoctoral researcher Symone
Alexander (center), and Peruvian field guide
Jaime Navarro adjust an ultrafast camera in
preparation for imaging a slingshot spider.GEOFF GALLICE; LAWRENCE E. REEVESREADY, SET... A slingshot spider prepares to
launch its cone-shaped web at a flying insect.
To do so, the spider will release a bundle of silk,
catapulting both the spider and the web.