Tunnel geometry of the Asian subterranean termite, Coptotermes gestroi (Blattodea: Heterotermitidae) in large arenas.

The Asian subterranean termite, Coptotermes gestroi (Wasmann), has never been intercepted in wooden stakes or in‑ground (IG) bait stations in South Florida. We used a large arena to test whether laboratory colonies of C. gestroi could intercept baits placed 3 m apart, following label specifications. In contrast to our field observations, these laboratory colonies readily intercepted baits in 13.1 ± 3.2 d, a rate not statistically different from the Coptotermes formosanus Shiraki (20.5 ± 3.5 d). The cause of this discrepancy between laboratory and field behavior is still under investigation. There were no significant differences in most tunnel‑geometry parameters between C. gestroi and C. formosanus. However, the secondary‑tunnel length distribution differed significantly, with C. gestroi constructing a greater number of shorter secondary tunnels than C. formosanus. Fractal analysis showed that C. formosanus produced more abundant and more complex tunnel networks than C. gestroi. A distinctive behavior in C. gestroi was observed when a tunnel approached within 17.8 ± 6.8 cm of a bait, at which point the tunnel shifted direction toward the bait. GC‑MS analysis and the use of new Plexiglas arena ruled out any involvement of trail‑following pheromones. Follow‑up experiments evaluating light, magnetism, bait odor, temperature gradients, colony age, and substrate type also failed to identify a causal mechanism. Despite clear behavioral evidence of short‑range bait detection, the sensory basis underlying this response in C. gestroi remains unresolved.