Trap-jaw ants can use their powerful mandibles to hurl themselves out of harm’s way when an antlion stalks, says a team of entomologists at the University of Illinois, Urbana-Champaign.
A worker of the trap-jaw ant Odontomachus brunneus. Image credit: Larabee FJ / Suarez AV.
The mandibles of the trap-jaw ant Odontomachus brunneus can whip shut at speeds over 40 meters per second, and are used for capturing prey, protection, and more routine tasks, such as digging nests or tending to ant larvae.
“Previous studies have reported that trap-jaw ants sometimes jump with their jaws, but it was unknown whether this behavior was meant to help them get away from a predator, and it wasn’t clear that it actually improved their odds of surviving an encounter with a predator,” said Fredrick Larabee, a graduate student at the University of Illinois and the first author of a paper published in the journal PLoS ONE.
“Previous research has showed that Odontomachus brunneus sometimes adopts an unusual body posture just before jumping. It lowers its head, making contact with the ground, and occasionally raises a leg before deploying its mandibles to hurl itself into the air,” added Prof Andrew Suarez, head of the University of Illinois’s Animal Biology Department.
To see if, and how often, the ants used the jaw-jumping maneuver to escape from an actual predator, Larabee and Prof Suarez the dropped trap-jaw ants into pits of antlions Myrmeleon carolinus in the lab.
Pit-building antlions have a two-part strategy for capturing prey. First, they dig conical pits in the sand and bury themselves at the bottom of the pit to wait for a victim.
“The ants were able to jump out of the pits about 15% 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. In this case a tool that is very good for capturing fast or dangerous prey also is good for another function, which is escape,” Larabee said.
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Larabee FJ, Suarez AV. 2015. Mandible-Powered Escape Jumps in Trap-Jaw Ants Increase Survival Rates during Predator-Prey Encounters. PLoS ONE 10 (5): e0124871; doi: 10.1371/journal.pone.0124871
