Trap-Jaw Ants Go Ballistic

Aug. 21, 2006 — The horn-like jaws of the trap-jaw ant snap shut at a speed of 78 to 145 mph, qualifying as the fastest known moving body parts, according to new research.

The jaws snap together with a force strong enough to hurl the ant 3 inches into the air and 8 1/2 inches away, the equivalent of a 5’6" human jumping 44 feet in the air and soaring for 132 feet.

"The ants generate their extreme (jaw) speeds through the use of power amplification – a combination of springs and latches which allow the animals to store up and release energy within their own body," said lead author Sheila Patek, who indicated that the system has an "internal damping" mechanism that prevents the powerful snap from crushing the ant.

"Trap-jaw ants slowly contract large muscles while a pair of latches keep the jaws open. Once the muscles are fully contracted, the latches are released and the jaws close explosively," she explained to Discovery News.

The findings are published in this week’s Proceedings of the National Academy of Sciences.

Patek and her team at the University of California at Berkeley studied worker ants of species Odontomachus bauri, collected in Costa Rica. Co-author Andrew Suarez told Discovery News that similar ants live in Florida and Arizona, but this particular species is only found in Central America and northern South America.

Using a high-speed video camera filming at 50,000 frames per second, the researchers also learned that the jaws serve at least two purposes.

The most frequent is "bouncer defense." Here, the ants – alone or cooperatively – attack an intruder, such as another ant or spider, with a snap of their jaws. The resulting force propels the trap-jaw ants into the air and away from any reciprocating attack.

Another tactic is called the "escape jump," in which an ant fires its mandibles against the ground, sending itself flying. The researchers don't think an ant can control the direction of a landing, but the impressive jumps and falls cannot injure the insects.

"It’s a simple rule of physics," Patek told Discovery News. "Small animals are not injured when they fall – they just don’t weigh enough to generate much force!"

When the insects employ the tactic in a group, it's called a "popcorn effect," confusing the lizards or other predators that feed on the ants in the leaf litter where they live.

Wulfila Gronenberg, associate professor of neurobiology, ecology and evolutionary biology at Arizona Research Laboratories, told Discovery News, "To my knowledge, the mandibles of these ants are the fastest moving body parts yet described."

A previous speed record, 2.7 milliseconds, was set by the kick of a mantis shrimp, but the trap-jaw snap clocked in at .13 milliseconds.