Close encounters among flying locusts produce wing-beat coupling

Any flying animal leaves behind a wake of turbulent air. Thus, a closely tailing neighbor may be buffeted by complex aerodynamic forces. We report here that pairs of tethered locusts (Locusta migratoria) flying in tandem in a wind tunnel, couple their wing-beats to one another. Wind-receptive hairs on the rear partner's head provide the main sensory input that produces the coupling. The phase angle of coupling depends upon the distance between the individuals. By phase-coupling to a forward neighbor's wake, a locust may turn this turbulence to its own aerodynamic advantage. Moreover, within a large swarm local groups of locusts may fly in a functionally integrated manner.