Brownian motion of fire ants hinders raft formation

When flooded, fire ants aggregate and form rafts to avoid drowning. Finding neighbors and attaching to them is a critical first step for raft formation. In this study, we observe individual fire ants perform random walk on the water surface. We characterize this exploratory behavior by measuring the orientational and translational diffusivity. Brownian motion of fire ants can be considered as thermal fluctuations which in turn inhibit the assembly of small rafts. Our results suggest that this repulsive mechanism is balanced by the attractive surface tension effect in the formations of larger rafts.