Pair formation in insect swarms driven by adaptive long-range interactions
Swarming is a form of collective animal behavior that has caught the attention of physicists, as a self-organized non-equilibrium system that remains cohesive although it exhibits no clear order parameter, as opposed to "flocking" behavior. Such behavior is observed in a variety of species, such as fish, bats and flying insects. We proposed a model whereby the interactions between the flying insects (midges) are mediated by acoustics due to the sound they emit while flying, and this gives rise to long-range (power-law) interactions. Furthermore, the response of the midges was proposed to be adaptive, as most sensory systems in biology are. The model described many of the mean-field features of the observed swarms.
In addition to steady-state features, recent observations have found intriguing formation of synchronized pairs of midges, which typically oscillate with respect to each other at higher frequency and with a small distance between them, while they move together through the swarm. However, no mechanism for this phenomenon has been established. In particular, it is not known if pairing is a result of new behavioral rules, or whether it can arise naturally as a passive byproduct of swarming. Here we report that pairing is a natural byproduct of the same model of adaptive long-range interactions (ALRI), without any modifications. Rather, pairing can be viewed as an emergent phenomenon, which is a natural outcome of the same interactions that lead to swarm formation.
Department of Chemical and Biological Physics Weizmann Institute of Science Rehovot, Israel