With the help of high-speed cameras, scientists have finally solved the mystery of how some ants can snap their jaws shut in half a millisecond—700 times faster than the blink of an eye.
Two species of Myrmoteras trap-jaw ant use a special set of joints and muscles to spring-load their massive mandibles before releasing them to slam shut on prey, according to a new study.
“Think of it like a giant crossbow, ready to fire,” says co-author Andrew Suarez, an entomologist at the University of Illinois. (See "Ant With Lightning Jaws Makes World's Fastest Strike.")
This system is completely different from the four other groups of trap-jaw ants, which use a simple combination of latch, spring, and trigger to catch their prey. The latch holds their jaws open so that the ants can use their muscles like a spring. This loads the jaws with tremendous amounts of power that are released when triggered.
Though the jaws look similar among the five types, Myrmoteras has its own mechanism—an example of what's called convergent evolution.
"These ants are nothing like the other species of trap-jaws,” says Suarez, who has nicknamed them monster ants. “They’re completely unique.” (Watch a trap-jaw spider move as quickly as the world's fastest runner.)
Adds Magdalena Sorger, an entomologist at North Carolina State University, “I don’t know that there’s another species of ant that’s as strange-looking as these."
Jaws at the Ready
While scientists have studied other groups of trap-jaw ant in detail, the rarely seen Myrmoteras, native to the Southeast Asian tropics has remained a mystery.
Suarez and study leader Fred Larabee, an entomologist at the Smithsonian's National Museum of Natural History, recorded the ants catching springtails, their primary prey, using video cameras that record at 50,000 frames per second.
The team noticed that while hunting, the ants keep their jaws open at a 280-degree angle—a strategy that stores elastic energy and allows them to shut their mandibles in a fraction of a second, according to the study, published August 30 in the Journal of Experimental Biology.
Reviewing the footage, the scientists calculated the jaws move at about 50 miles per hour.
That's actually slower than other trap-jaw ants, such as Odontomachus, which make among the fastest animal movements on Earth. It's likely that Myrmoteras don't need that kind of speed to catch springtails, the authors note.
Reviewing the footage, the scientists saw something peculiar: A small divot that formed at the back of the ants’ heads when the insects opened their jaws.
To investigate this further, the team put ant specimens through a micro CT scanner designed to pinpoint anatomical details in animals. (Also read "The High-Flying Ant With a Bite Like a Bear Trap.")
The scans revealed two crucial, never-before-seen sets of muscles: A large set that load the jaws with potential energy—generating enough force to create that small indentation on the back of the head—and a smaller set that releases the jaws when it senses the trigger.
“We know pretty little about these ants—that’s why this paper is kind of a big deal," says Sorger, who studies Odontomachus ants but wasn't involved in the new study.
"They used really cutting-edge techniques to study a beautiful example of convergent evolution."