Multifunctionality and mechanical origins: Ballistic jaw propulsion in trap-jaw ants

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 103; no. 34; pp. 12787 - 12792
• Main Authors: Patek, S.N, Baio, J.E, Fisher, B.L, Suarez, A.V
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 22-08-2006; National Acad Sciences
• Subjects: Animals; Ants; Ants - anatomy & histology; Ants - physiology; Beginning teachers; Behavior, Animal; Biological Sciences; Biology; Biomechanical Phenomena; Bouncers; feeding behavior; Formicidae; Insect behavior; Insect traps; Jaw; Jaw - anatomy & histology; Jaw - physiology; Jumping; kinematics; locomotion; Mandible; mandible strike kinematics; mechanical properties; mouthparts; Movement; Odontomachus bauri; physical activity; Predation; Propulsion; Speed; Time Factors; Trajectories; trap-jaw mechanism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0604290103

Extreme animal movements are usually associated with a single, high-performance behavior. However, the remarkably rapid mandible strikes of the trap-jaw ant, Odontomachus bauri, can yield multiple functional outcomes. Here we investigate the biomechanics of mandible strikes in O. bauri and find that the extreme mandible movements serve two distinct functions: predation and propulsion. During predatory strikes, O. bauri mandibles close at speeds ranging from 35 to 64 m·s⁻¹ within an average duration of 0.13 ms, far surpassing the speeds of other documented ballistic predatory appendages in the animal kingdom. The high speeds of the mandibles assist in capturing prey, while the extreme accelerations result in instantaneous mandible strike forces that can exceed 300 times the ant's body weight. Consequently, an O. bauri mandible strike directed against the substrate produces sufficient propulsive power to launch the ant into the air. Changing head orientation and strike surfaces allow O. bauri to use the trap-jaw mechanism to capture prey, eject intruders, or jump to safety. This use of a single, simple mechanical system to generate a suite of profoundly different behavioral functions offers insights into the morphological origins of novelties in feeding and locomotion.