Flying honeybees adjust their reaction times to enable group cohesion

Flying insects routinely demonstrate coordinated flight in groups. How they achieve this with very limited communication, vision, and neural systems remains an open question. We measured the visual reaction time in flying honeybees while they chased a moving target, and compared in-flight reaction times for solo animals with those flying in groups. Across 425 insects, the solo honeybees show diverse reaction times (an average of 30ms and a standard deviation of 50ms). The reaction times in groups are significantly more uniform (an average of 15ms and a standard deviation of only 7ms), indicating that honeybees in group flight adjust their reaction times to match their neighbors. To investigate the role of this adjustment, we curve fit the reaction time distributions and analyzed them in a mathematical model of swarming, finding that the reaction time increases the stable region of a cohesive swarm. To verify the stabilizing effect was not an artifact of curve fitting, we then inserted the measured delays in a swarm simulation, which breaks apart under the solo reaction times and achieves stable formations for the group reaction times. Together, our findings highlight how flying animals can synchronize their reaction times in group flights to improve group cohesion.