An Adaptive Gravity Model for Interactions in Insect Swarms

The collective motion of groups of animals emerges from the net effect of the interactions between individual members of the group. In many cases, such as birds, or fish, these interactions are mediated by sensory stimuli that predominantly arise from nearby neighbors. But not all stimuli in animal groups are short range. Here, we consider mating swarms of midges, which interact primarily via long-range acoustic stimuli. We exploit the similarity in form between the decay of acoustic and gravitational sources to build a model for swarm behavior. By accounting for the adaptive nature of the midges’ acoustic sensing, we show that our “adaptive gravity” model makes predictions that agree well with experimental observations of laboratory swarms. Our results highlight the role of sensory mechanisms and interaction range in collective animal behavior. They also open a new class of adaptive forces. We find that adaptivity endows swarms with a natural mechanism for stabilization, allowing them to avoid the equivalent of gravitational collapse.