Figure 2.

Overview of the experimental set-up and digging arena. (a) Time lapse images were collected from eight arenas simultaneously using a rotating camera. (b) Quasi-two-dimensional digging arenas were filled with a substrate of wetted 0.25 ± 0.04 mm diameter glass particles. Tunnels extend downwards vertically from the surface and branch subsurface forming a connected network of paths. Excavated material was deposited by the ants in a loosely packed pile on the surface. (c) Tunnel networks were represented as binary image masks. (d) The network representation considers tunnels as edges and the branch and endpoints as vertices. (Online version in colour.)