The auditory system of last instars in Gryllus bimaculatus DeGeer

Aspects of the auditory development of Gryllus bimaculatus are compared with those of other Orthopterans and Mantodea. Auditory receptor cell branching patterns and first‐order auditory interneurones of last‐instar crickets are morphologically very similar to adult cells; auditory thresholds are 30–45 dB higher in last instars than in adults; the ears of most ultimate nymphs lack directionality; and the tympana of last instars are not set apart clearly from the surrounding cuticle, are still thick, backed by a thick layer of epithelium, and lack microtrichia. Thus, the development of the auditory system from last‐instar to adult shows close similarities between G. bimaculatus and Teleogryllus commodus but not to other Orthopteran or Mantid species. This supports the hypothesis that the pattern of post‐embryonic development of the auditory system in crickets differs significantly from that in other Orthopterans and in Mantodea.