Variation in the stridulatory apparatus in Mycotrupes beetles (Coleoptera: Geotrupidae)

The pars stridens of the coxo-abdominal stridulatory apparatus is described for the first time in Mycotrupes. Located on the hind coxa, the pars stridens consists of an elongate, raised area covered with ribs. These ribs are scraped with a plectrum, producing a rasping or squeaking sound. Variation in the pars stridens was studied across all five known species of Mycotrupes. Species-specific differences were discovered in the numbers of ribs contained on this structure, while no sexual differences were observed. Stridulations produced by the pars stridens were found to be extremely variable both within individuals and across species. The possible behavioral significance of these signals in Mycotrupes is discussed.