Video: ‘Trap-jaw’ spiders chomp down with surprising force

Many spiders spin webs to capture their quarry—but that’s not the only strategy hungry arachnids employ. When a tasty target is near, Mecysmaucheniidae spiders (Semysmauchenius sp., video; Mecysmauchenius sp., photograph) spread their jaws open, stalk their prey, then seize it by snapping their powerful mandibles shut. (The strike in this slowed-down video would be 150 times faster if played at full speed.) In the lab, scientists teased the arachnids, which are mere millimeters long, with an eyelash affixed to a pin. The researchers recorded the spiders’ reactions with high-speed cameras, then calculated the speed and power of their bites. Four out of 14 tested species clamp their jaws together in about half a millisecond or less, faster than muscle power alone would allow, and the swiftest strikes required about 200 times more power than the peak of what human leg muscles exert when their owner jumps. Although some ants also exhibit these “power-amplified” jaw snaps, scientists hadn’t previously witnessed arachnids producing them. The spiders must be storing energy, the researchers say, then releasing it when they strike—the same way the spring in a mousetrap stows energy until the trap snaps, and with similarly lethal results. The authors of the study, published online today in Current Biology, aren’t sure where in their bodies the spiders are tucking away that energy reserve, but they report that the species capable of the fastest chomps have thicker tendons and facial plates than their slower relatives.

(Video credit: H. Wood)