Meeting Abstract

112.7  Tuesday, Jan. 7 11:45  Fire ants repair bridges in response to vibration PHONEKEO, S*; CANTOR, A; HUANG, Q; HU, D; Georgia Institute of Technology ; Georgia Institute of Technology ; Tsinghua University; Georgia Institute of Technology

To cross gaps in their path, fire ants link their bodies together to form a bridge. Ant bridges, like rafts and bivouacs are built without coordinated leadership, but instead using local rules from which the structure gradually emerges. Such bridges are sometimes built on unstable surfaces such as leaves or reeds, which can be perturbed by passing waters or winds. In this experimental study, we use time-lapse videography to visualize the self-repair of fire ant bridges in response to periodic shaking of the bridge's endpoints. Shaking causes ants in tension to contract their limbs, reducing the bridge's arc length and increasing its rigidity. Shaking also causes ants walking along the bridge to veer from points of high acceleration, congregating instead at the bridge's endpoints. The combined action of these behaviors reduces the amplitude of vibration of the bridge's midpoint, which decreases the bridge's internal stresses along its entire length, a consequence that is adaptive for all ants within the bridge.