Construction of non-equilibrium structures by insect aggregations: the case of fire ants

Active matter networks are ubiquitous in nature and synthetic materials, ranging from molecular-scale polymers to macroscale swarms of social insects. These materials are characterized by their transient, reversible crosslinks and non-equilibrium state. Due to these reversible bonds and non-equilibrium states, active matter networks can exhibit directed viscous flow and morphogenesis. One such set of active matter networks is the aggregations formed by the bodies of red imported fire ant (Solenopsis invicta). These ants aggregate into floating rafts when placed in water, and will form steady-state, convective towers if given vertical rods around which to nucleate. In this presentation, we explore the mechanical rules individual fire ants follow on the surfaces of these towers by measuring their statistical velocity distribution, parking rates, and unparking rates, through imaging analysis. We then present and numerically employ a theoretical framework, that bridges these physical rules to the emergent behavior, to replicate the global morphologies observed. Thus, verifying that the postulated physical rules explain the global morphological response of this active matter system and generally informing our understanding of what drives these collective mechanical phenomena.