Collective mechanical properties of insect swarms*

Social animals routinely form groups, which are thought to display emergent, collective behavior. This suggests that animal groups should have properties at the group scale that are not directly linked to the individuals, much as bulk materials have properties distinct from those of their constituent atoms. We show that laboratory insect swarms possess emergent mechanical properties, displaying a collective viscoelastic response to applied oscillatory visual stimuli. We find that the swarms strongly damp perturbations. Thus, unlike bird flocks, which appear to use collective behavior to promote lossless information flow through the group, our results suggest that insect swarms use it to stabilize themselves against environmental perturbations.