title: On the tensile strength of insect swarms.
abstract: Collective animal groups are often described by the macroscopic patterns they form. Such global patterns, however, convey limited information about the nature of the aggregation as a whole. Here, we take a different approach, drawing on ideas from materials testing to probe the macroscopic mechanical properties of mating swarms of the non-biting midge Chironomus riparius. By manipulating ground-based visual features that tend to position the swarms in space, we apply an effective tensile load to the swarms, and show that we can quasi-statically pull single swarms apart into multiple daughter swarms. Our results suggest that swarms surprisingly have macroscopic mechanical properties similar to solids, including a finite Young's modulus and yield strength, and that they do not flow like viscous fluids.
authors: Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors: Rui
authors: R
authors: Ni
authors: Nicholas T
authors: NT
authors: Ouellette
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002683:Chironomidae / Q000502:physiology*; D055119:Elastic Modulus; D005260:Female; D008297:Male; D012726:Sexual Behavior, Animal; D012919:Social Behavior; D013718:Tensile Strength; D014796:Visual Perception