Tunnel volume regulation and group size of subterranean termites

Tunnel volumes excavated by laboratory groups of the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the eastern subterranean termite, Reticulitermes flavipes (Kollar), were measured by using 2-dimentional foraging arenas. Group sizes of 20, 40, 60, 80, 100 and 200 termites were used for the study. Analysis of the images of tunnels taken hourly showed tunnel volume increased and eventually reached the equilibrium for both termite species, but C. formosanus reached the equilibrium faster at lower level than R. flavipes. C. formosanus constructed fewer primary tunnels with less branching than R. flavipes, and no additional tunneling activity was observed once the tunnel volume reached the equilibrium. R. flavipes, on the other hand, continued tunnel excavation even after reaching the equilibrium, but the equilibrated volume was maintained by filling unused tunnels with sand excavated from newly dug tunnels.