Effect of soldiers on collective tunneling behavior in three species of Reticulitermes (Blattodea: Rhinotermitidae)

In social insects, behavioral changes are shaped by social context which includes the presence of other castes. Soldiers play a critical role in the defense of a termite colony, although their role beyond defense is less understood. Termites tunnel to safely acquire resources, producing an extended phenotype of the colony shaped by various environmental and genetic factors. In this study, we investigated the indirect influence of the soldier on worker tunneling behavior for three species of Reticulitermes subterranean termites. Groups of 50 worker termites containing either three, one, none, or the cuticular extract of soldiers were placed into planar arenas and allowed to tunnel. The speed and morphology of tunnel construction were determined for the first 36 h of tunneling. We found tunneling differences among species: R. flavipes (Kollar) produced more branches and tunneled faster than both R. hageni Banks and R. virginicus (Banks). Trials with live soldiers produced more branches in R. flavipes , while trials with live soldiers or even the chemical extract of a soldier increased tunnel speed in R. flavipes and accelerated tunnel initiation in R. hageni . In R. virginicus , there was little impact of soldiers. These behavioral changes in R. flavipes and R. hageni may reduce the chance of tunneling workers encountering enemies without soldiers present. All three species used dead reckoning to maintain a straight direction after being forced through two sharp turns, but the presence of soldiers had no influence on this ability. This study, showing that soldiers can influence tunneling behavior in workers in some species, provides additional evidence of the keystone role of soldiers in termite colonies, and demonstrates that this influence can be exerted through chemical cues alone in some species.