Decentralized Traffic Flow and Congestion in Termite Collectives

Collective movement in social insects provides valuable insights into the physics of traffic flow and congestion. This study investigates the traffic dynamics of tens of thousands of subterranean termites navigating congested pathways and bottlenecks within narrow tunnels dug in a thin layer of sand. Observations reveal that individual termites align their movements along a common direction, analogous to molecules in a nematic liquid crystal phase. This collective alignment leads to oscillatory traffic patterns characterized by alternating densely packed clusters and sparse distributions, resembling the stop-and-go waves observed in human vehicular traffic. Such behavior mirrors the "glug-glug" phenomenon in fluid mechanics, where intermittent flow arises due to pressure fluctuations and bottleneck constraints. Remarkably, termites in congested conditions demonstrate significant flexibility, effortlessly bending and executing U-turns, which enhances their ability to navigate crowded spaces. In contrast, ants often form well-organized, bidirectional trails with adaptive behaviors like lane formation and speed adjustments to minimize congestion. These observations highlight how physical form and structural flexibility influence function in eusocial collectives, providing insights into the physics of flow in complex systems.