Surface irregularity induced-tunneling behavior of the formosan subterranean termite

Subterranean termites forage from place to place by tunneling through soil. In order to examine termite-tunneling responses to external factors, we designed a square arena that contains five introduction chambers connected with narrow paths, which was filled with sand. Triangle-shaped indentation with width W and height H was provided as surface irregularity on the sand facing the introduction chambers by using templates. After termites were introduced into the chambers, we measured elapsed time, τ, for a tunnel to reach the point at 3 mm away from the apex of the irregularity. We found that for W = 0 mm (the absence of irregularity), termites (Coptotermes formosanus Shiraki) did not tunnel for ∼7 h, whereas, for W = 1, 2, 3, and 4 mm, they exhibited the tunneling behavior within 20 min. The result indicated that the presence of surface irregularity is essential to induce termite tunneling. In addition, we found that W was correlated with τ, whereas H did not influence τ. This was briefly discussed in the context of individual movement behavior.