Asymmetrical "snapping" mandibles in termites converge in form with composite bows developed by archers of the Eurasian steppe

Arthropods make use of the gradual loading of energy onto elastic springs to perform motions that are far more swift and powerful than can be achieved by direct muscular action.  Termite soldiers of a morphological group known as "symmetrical snapping" contract a pair of long, slim mandibles against each other which deform gradually storing energy until a rapid release as they slip past each other and strike a lateral foe.  Mechanically, this process resembles the deformation and release of a simple human longbow, the length of which adds the mechanical advantage of a long lever arm to facilitate drawing.  Another morphological type of soldier with “asymmetrical snapping” mandibles has originated at least four times from symmetrical snapping ancestors.  The function of the mandibles has been poorly understood.  Early speculation ranged from the production of alarm vibrations to aiding in tunneling by pulverizing hard soil.  While the most comprehensive modern treatments of comparative termite soldier morphology have recognized that across the group the left mandible functions as a spring to store potential energy, they incorrectly identified the striking mandible as the inflexible right mandible, which would strike a foe laterally to the left.   In fact, the striking mandible is the flexible left mandible, with the right simply plucking the “bow” to deform it.  Moreover the complex “S” shaped curve of the left mandible is a means of transforming what would have been a lateral blow to a strike directly ahead of the termite.  In the confines of a tunnel this would be a devastating weapon, striking a foe without allowing it to come to grips.  The mandible resembles in form and function the complex architecture of the most highly advances human composite bows.  These were developed over a process that took millennia that maximized the weight or energy the bow could store while still being able to be drawn by hand.  Like these bows, the mandible consists of a short section of spring and a long lever arm that aids in bending it.  The potential energy stored in the mandibles of different species of asymmetrical snapping termites is presented, along with the force-draw curves.