- Invited
Small fire ant rafts are unstable
Phys. Rev. Fluids 7, 090501 – Published 20 September, 2022
DOI: https://doi.org/10.1103/PhysRevFluids.7.090501
Abstract
In this combined experimental and numerical study, we film the formation of fire ant rafts to determine how they cohere together. Surprisingly, we discover that ants prioritize separation and exploration: they flail legs and bounce off neighbors when they collide. Despite the active repulsion, fire ants cohere by the Cheerios effect, a capillary force that attracts small floating objects such as breakfast cereal. Experiments reveal that rafts consisting of fewer than ten ants disintegrate within minutes. Predictions by a Langevin model reproduce the stability transition and the critical raft size, which emerges from the balance between their mutual repulsion and the Cheerios effect. This work may inspire physically grounded models for the behavior of natural swarms.
