Trap-jaw ants are fearsome predators with jaws that can snap closed at speeds near 100 miles per hour. It's one of the fastest animal movements that's ever been recorded.
But when forced to go head-to-head with hungry antlions, they use their jaws not to fight, but for flight instead, according to a study published today in the journal PLOS One.
"Trap-jaw ants can use their mandibles not just for prey capture, but also for escaping predators," lead author Frederick Larabee of the University of Illinois, Urbana-Champaign, said in an interview.
To other ant-sized creatures, antlions are as menacing as they sound. These predatory insects dig pits in sandy soil, bury themselves in the bottom, and wait with open jaws peeking out for unsuspecting insects to fall into their trap.
While Larabee points out that "trap-jaw ants are also fearsome predators in their own right," antlions are formidable opponents. Trap-jaw ants have a tough time climbing out of antlion pits, as they often end up causing miniavalanches and falling back in toward the antlion's maw.
When Larabee and his colleague Andrew Suarez observed how the trap-jaw ant Odontomachus brunneus defends itself against antlions, they found that they frequently use their jaws to catapult themselves out of the pit.
"They orient their open jaws toward the side or center of the pit and then release the strike against the sand," Larabee says. "All that force then gets reflected back at them and their head jerks back and they are flung into the air and end up doing these somersaults as they fly out of the pits."
Here's a video of a trap-jaw ant saving its life with this technique.
...and one that wasn't so successful.
Gluing the mandibles of some trap-jaw ants shut made it clear that this strategy is key to surviving antlion encounters. Trap-jaw ants with working mandibles survived twice as often as those whose jaws were glued shut because they were able to fling themselves out of danger.
The findings illustrate evolution's thriftiness, constantly repurposing structures and behaviors to benefit organisms in new ways.
"These findings show that complex multifunctional behaviors like spring-loaded, power-amplified jaws can be co-opted from one purpose, in this case prey capture, to another, defense," says Larabee.
The PLOS One article can be found here.
Photo: Bernard Dupont | Flickr
