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article imageIn a pinch: Trap jaw ants use powerful jaws to escape death traps

By Megan Hamilton     May 17, 2015 in Science
The trap-jaw ant has earned the reputation of making short work of its prey. With herculean, spring-loaded mandibles, it crushes its prey with ease and defends its nests.
Scientists have recently discovered it has another nifty use for those jaws.
In a study published in PLOS ONE, entomologists Fredrick Larabee and Andrew Suarez provided evidence that trap-jaw ants can also use their high-velocity mandibles for "ballistic jaw propulsion." In other words, they can open their jaws to 180 degrees before snapping them shut at 140 miles per hour, arstechnica reports.
"They produce so much force that when they strike [a part of the ground] that's relatively immovable, that force gets projected back on the ant and they go flying through the air," Suarez told National Geographic, which helped fund the study.
At first, the scientists didn't know if the insects were doing this to intentionally fling themselves to safety, or if it was a lucky misfire when fighting a predator. Now, after studying the critters, it seems that trap-jaw ants really do resort to acrobatics as a way of hurling themselves to safety, and that comes in handy when they have to deal with their fiercest predator, the antlion.
"Previous research has showed that Odontomachus brunneus [trap-jaw ants] sometimes adopts an unusual body posture just before jumping," said Suarez, head of the University of Illinois's Animal Biology Department, per Sci-News.com. "It lowers its head, making contact with the ground, and occasionally raises a leg before deploying its mandibles to hurl itself into the air."
The scientists wanted to see if the ants really did use the jaw-jumping tactic to escape from trouble, and how often they did this, so Larabee and Suarez dropped the ants into pits of antlions in the lab.
Now, antlions have a two-part strategy for capturing dinner. They start out by digging conical pits in the sand. Then they bury themselves at the bottom of the pit to wait for their meal ticket.
"The ants were able to jump out of the pits about 15 percent of the time in their encounters with antlions," Larabee said. "But when we glued their mandibles shut before dropping them in the pits, they couldn't jump at all. It cut in half their survival rate."
"This study may show how a trait or capability that evolved for one purpose can be adapted for different uses," he said. "In this case a tool that is very good for capturing fast or dangerous prey also is good for another function, which is escape."
So how do these formidable jaws work?
Well, the jaws work like a trigger. Tiny muscles in the head of these ants pull the mandibles back into position, where they are locked in place by a latch that's part of the mandible joint, Understanding Evolution reports. When the ant is about to bite, it contracts large muscles in its head. These muscles pull against the latch and once they are contracted, the ant's jaws are cocked. When the trigger muscle releases the latch, the jaws are snapped together.
O. brunneus is native to Central and South America.
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