In a study published today in the journal Royal Society Open Science, researchers examined the kinematics and functional morphology of the Dracula ant (Mystrium camillae), who use a snap-jaw mechanism to quickly slide their mandibles across each other similar to a finger snap. The analysis revealed that Dracula ant mandibles complete their strike in as little as 23 µsec and reach peak velocities of 90 m/s (more than 200 mph), making them the fastest known animal appendage.
The Dracula ant (Mystrium camillae) can snap its mandibles at speeds of up to 90 m/s. Image credit: Adrian Smith.
“The high accelerations of Mystrium strikes likely result in high-impact forces necessary for predatory or defensive behaviors,” said University of Illinois Professor Andrew Suarez and co-authors.
“These ants are fascinating as their mandibles are very unusual.”
“Even among ants that power-amplify their jaws, the Dracula ants are unique: instead of using three different parts for the spring, latch and lever arm, all three are combined in the mandible.”
Unlike trap-jaw ants, whose powerful jaws snap closed from an open position, Dracula ants power up their mandibles by pressing the tips together, spring-loading them with internal stresses that release when one mandible slides across the other, similar to a human finger snap.
“The ants use this motion to smack other arthropods, likely stunning them, smashing them against a tunnel wall or pushing them away,” Professor Suarez said.
“The prey is then transported back to the nest, where it is fed to the ants’ larvae.”
“Scientists have described many different spring-loading mechanisms in ants, but no one knew the relative speed of each of these mechanisms,” added study first author Dr. Fredrick J. Larabee, a postdoctoral researcher at the Smithsonian National Museum of Natural History.
“We had to use incredibly fast cameras to see the whole movement.”
The scientists also used X-ray imaging technology to be able to see their anatomy in 3D, to better understand how the movement works.
They then conducted computer simulations of the mandible snaps of different castes of Dracula ants to test how the shape and structural characteristics of the mandibles affected the power of their snap.
“Our main findings are that snap-jaws are the fastest of the spring-loaded ant mouthparts, and the fastest currently known animal movement,” Dr. Larabee said.
“By comparing the jaw shape of snapping ants with biting ants, we also learned that it only took small changes in shape for the jaws to evolve a new function: acting as a spring.”
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Fredrick J. Larabee et al. Snap-jaw morphology is specialized for high-speed power amplification in the Dracula ant, Mystrium camillae. Royal Society Open Science, published online December 12, 2018; doi: 10.1098/rsos.181447
