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Dracula Ant - Mystrium camillae
Dracula Ant - Mystrium camillae

[Image: camillae1-L.jpg]

Scientific classification
Kingdom:  Animalia
Phylum:  Arthropoda
Class:  Insecta
Order:  Hymenoptera
Family:  Formicidae
Subfamily:  Amblyoponinae
Tribe:  Amblyoponini
Genus:  Mystrium
Species:  Mystrium camillae

Mystrium is a rare genus of ants in the subfamily Amblyoponinae. First described by Roger (1862) with the description of the queen of M. mysticum, the genus contains 14 species, all of which occur in the rainforests of the Old World with over half of the species endemic to the Malagasy region.

According to the revision of Mystrium in the Indo-Australian region (Bihn and Verhaagh 2007), Mystrium camillae is widely distributed in the Indomalaya, and Australian regions: from Australia to Brunei, China, India, Indonesia, Malaysia, Myanmar, Papua New Guinea, the Philippines and Singapore. We find that specimens currently determined as M. camillae display remarkable morphological variation, some of which appears not to be intra-specific but rather due to differences among species. For example, we found a small-sized queen with vestigial wings in Indonesian material, workers with longer setae on the anteromedial portion of the clypeus in specimens from New Guinea, a large queen with simple setae on the pronotal dorsum in specimens from China, and a strange yellow male from Australia. A reexamination of the species boundaries of Mystrium camillae based on a detailed comparative study using comprehensive colony samples from each local region is needed. (Yoshimura and Fisher 2014)

Mystrium are predators that specialize on capturing large centipedes. The long mandibles appear to be adapted to gripping what can be fast moving centipedes, and hold them in place to allow their being stung in the softer areas between their body segments. Foragers carrying out this task also need to have strong mandibular muscles that combined with their long mandbiles may compromise their efficiency in regards to brood care. Mystrium rogeri exhibits caste polymorphism where large workers appear to be specialized for foraging while smaller workers are adapted to specialize on brood care. Colonies of Mystrium oberthueri have large workers and many small reproductives. The vast majority of the the latter do not mate, do not leave the nest and both care for brood and are active in cleaning their nests. Colony size tends to be small (< 200 workers) and in some species, e.g., Mystrium rogeri, reproduction is based on having a single large queen morph that found nests independantly. In others, intermoph queens exist and colony founding can occur via fission.

Dracula ants possess fastest known animal appendage: The snap-jaw

December 11, 2018, University of Illinois at Urbana-Champaign

[Image: draculaantsp.jpg]
The mandibles of the Dracula ant, Mystrium camillae, are the fastest known moving animal appendages, snapping shut at speeds of up to 90 meters per second. Credit: Adrian Smith

Move over, trap-jaw ants and mantis shrimp: There's a faster appendage in town. According to a new study, the Dracula ant, Mystrium camillae, can snap its mandibles at speeds of up to 90 meters per second (more than 200 mph), making it the fastest animal movement on record.

"The high accelerations of Mystrium strikes likely result in high-impact forces necessary for predatory or defensive behaviors," the researchers wrote in a report of their findings in the journal Royal Society Open Science.

"These ants are fascinating as their mandibles are very unusual," said University of Illinois animal biology and entomology professor Andrew Suarez, who led the research with Fredrick J. Larabee, a postdoctoral researcher at the Smithsonian National Museum of Natural History; and Adrian A. Smith, of the North Carolina Museum of Natural Sciences and North Carolina State University, Raleigh. "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 researchers said.

"The ants use this motion to smack other arthropods, likely stunning them, smashing them against a tunnel wall or pushing them away. The prey is then transported back to the nest, where it is fed to the ants' larvae," Suarez said.

"Scientists have described many different spring-loading mechanisms in ants, but no one knew the relative speed of each of these mechanisms," Larabee said. "We had to use incredibly fast cameras to see the whole movement. We also used X-ray imaging technology to be able to see their anatomy in three dimensions, to better understand how the movement works."

The team also 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," 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."

The team's future work includes examining how the ants use their mandibles in the field.

"Their biology, how they capture prey and defend their nests, is still in need of description," Smith said.

Journal Reference:
Fredrick J. Larabee, Adrian A. Smith and Andrew V. Suarez Snap-jaw morphology is specialized for high-speed power amplification in the Dracula ant, Mystrium camillae, Royal Society Open Science

What is the limit of animal speed and what mechanisms produce the fastest movements? More than natural history trivia, the answer provides key insight into the form–function relationship of musculoskeletal movement and can determine the outcome of predator–prey interactions. The fastest known animal movements belong to arthropods, including trap-jaw ants, mantis shrimp and froghoppers, that have incorporated latches and springs into their appendage systems to overcome the limits of muscle power. In contrast to these examples of power amplification, where separate structures act as latch and spring to accelerate an appendage, some animals use a ‘snap-jaw’ mechanism that incorporates the latch and spring on the accelerating appendage itself. We 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. Kinematic analysis of high-speed video revealed that snap-jaw ant mandibles complete their strike in as little as 23 µsec and reach peak velocities of 90 m s−1, making them the fastest known animal appendage. Finite-element analysis demonstrated that snap-jaw mandibles were less stiff than biting non-power-amplified mandibles, consistent with their use as a flexible spring. These results extend our understanding of animal speed and demonstrate how small changes in morphology can result in dramatic differences in performance.
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