Effect of soldier proportion on tunneling behavior of Formosan subterranean termite Coptotermes formosanus (Blattodea: Rhinotermitidae)

Termites are eusocial insects that live in organized colonies consisting of reproductives, workers, and soldiers. The soldier caste is morphologically specialized for colony defense, but their morphology prevents them from feeding, tunneling, and self-grooming. The soldier caste is energetically expensive to maintain as the worker caste is responsible for grooming and feeding the soldiers. The Formosan subterranean termite, Coptotermes formosanus Shiraki, maintains a higher proportion of soldiers (about 10%) than the subterranean termites in Reticulitermes (< 2%). The high soldier percentagemay suggest that soldiers have roles in the colony other than defense. Previous studies have shown soldiers mediate food exploration in a higher termite (Nasutitermes costalis) and subterranean termite (C. intermedius), and we have observed soldiers of C. formosanus often located at the distal end of foraging tunnels, suggesting a potential role in foraging behavior. In this study, we tested the hypothesis that different soldier proportions influence the efficiency of tunneling activity and food collection in C. formosanus. Using two-dimensional foraging arenas (30 × 30 cm), we analyzed the foraging behavior of groups of 100 workers with the addition of 0, 2, 10 or 30 soldiers. We found that different soldier proportions did not significantly affect tunnel length, tunnel intersections, feeding station interception, and food consumption over 96 hours. The results imply that soldiers do not directly influence foraging behavior of workers. Further studies are needed to investigate the effect of soldiers in other social contexts, such as the presence of reproductives and predator/competitor stress.