Geometric difference between shelter tubes and tunnels of the Asian subterranean termite, Coptotermes gestroi (Wasmann) (Blattodea: Heterotermitidae)

Termites construct diverse foraging structures adapted to their environment. Subterranean tunnels are built through excavation in soil, while aboveground shelter tubes are constructed by depositing soil to traverse exposed surfaces safely. While tunneling behavior has been extensively studied, little is known about how termites construct shelter tubes above ground and how these structures may differ geometrically from subterranean tunnels. This study investigated whether differences in their environment affect the geometry of aboveground and underground foraging structures in the Asian subterranean termite, Coptotermes gestroi (Wasmann). We hypothesized that shelter tubes, built in exposed environments, would differ significantly in their geometry from tunnels due to building strategies and increased predation and desiccation risk. Using mature laboratory colonies (over seven years old), we compared five geometric components—total length, branching frequency, construction speed, orientation, and branch angle—between shelter tubes and subterranean tunnels. Shelter tubes were significantly longer and more highly branched than subterranean tunnels, despite no difference in orientation, branch angle, or construction speed. These results suggest that termites construct more expansive and denser networks when operating above ground, possibly to ensure protection during exploration in exposed environments. Overall, our findings indicate that C. gestroi modifies its foraging architecture based on their environment, but retains shared construction rules such as radiating paths and rounded corners across tunnels and shelter tubes. These behaviors reflect a flexible, yet conserved, foraging strategy shaped by ecological pressures.