Effect of soldiers on vibroacoustic alarm response in workers of subterranean termites (Blattodea: Rhinotermitidae)

Abstract

Subterranean termites rely on chemical and vibroacoustic communication as they live enclosed in tunnels in the soil or wood. While social context is known to influence colony-level behaviors in many social insects, its influence on alarm communication remains unstudied. We tested the influence of the soldier caste on worker behavioral plasticity for subterranean termites: two species of Reticulitermes and Coptotermes formosanus. We altered the group composition according to soldier proportion or their replacement by chemical signals (hexane extracts). The responses of termites to stimuli known to provoke alarm responses, such as human breath simulating a breech in the nest or crushed soldier head (CSH) containing the chemical alarm cues, comprised increased movement and increased vibroacoustic alarm signaling. Species differed in the intensity of their responses, which were generally stronger in Reticulitermes. Groups of Reticulitermes with soldiers responded more strongly to CSH, while groups of R. virginicus only responded to human breath in the presence of soldier extracts. The responses of Coptotermes formosanus showed no effect of group composition on responses to stimuli, suggesting that soldier presence does not affect vibroacoustic behavior in this species. Our results highlight how alarm behavior changes quickly in closely related species as part of finely tuned behavioral mechanisms optimizing a species’ response in each environment including in the presence of natural predators and competitors.