Bioacoustics of Trachymyrmex fuscus, Trachymyrmex tucumanus, and Atta sexdens rubropilosa (Hymenoptera: Formicidae)

The capability to produce species-specific sounds is common among ants. Ants of the genus Trachymyrmex occur in an intermediate phylogenetic position within the Attini tribe, between the leafcutters, such as Atta sexdens rubropilosa, and more basal species. The study of stridulations would provide important cues on the evolution of the tribe’s diverse biological aspects. Therefore, in the present study, we described the stridulation signals produced by Trachymyrmex fuscus, Trachymyrmex tucumanus, and A. sexdens rubropilosa workers. Ant workers were recorded, and their stridulatory organs were measured. The following parameters were analyzed: chirp length [ms], inter-chirp (pause) [ms], cycle (chirp + inter-chirp) [ms], cycle repetition rate [Hz], and the peak frequency [Hz], as well as the number of ridges on the pars stridens. During the inter-chirp, there is no measurable signal for A. sexdens rubropilosa, whereas for Trachymyrmex fuscus and Trachymyrmex tucumanus, a low intensity signal was detected. In other words, the plectrum and the pars stridens of A. sexdens rubropilosa have no contact during the lowering of the gaster. Principal component analysis, to which mainly the duration of chirps contributed, showed that stridulation is an efficient tool to differentiate ant species at least in the case of the Attini tribe.