The dynamics of microjet spitting in termite soldiers

Tropical cone-head termite soldiers (Nasutitermites sp.) spit a sticky, noxious liquid jet through their nozzle-shaped heads to defend their nests from invaders. While previous work qualitatively described these insects' spitting behavior, how their jets' fluid dynamics aid them in 'fortress defense' is still unknown. In this talk, we uncover the fluid dynamics and physical properties of these minute jets (V ~10 nL, D ~ 10 μm) taken in the Peruvian Amazon rainforest with high-speed imaging and micro-rheological experiments. We mathematically and experimentally show that these termites exploit head oscillations to transition from generating liquid rope coils to producing large lasso-like viscous threads (x 2-3 body length) to ward off larger predators. Combining micro-CT scans with computational fluid dynamic simulation, we model the pressure-driven flow across their pointed head (nasus) and show how its geometry influences the jet dynamics. Understanding the biomechanics of these termites and the fluid mechanics of the microjets ejected by them will not only advance the knowledge of the biophysical limits of these termites' defensive behavior but might also guide the design of jet extrusion nozzles at the microscale.