Original Paper

Journal of Comparative Physiology A

, Volume 200, Issue 2, pp 139-148

Open Access This content is freely available online to anyone, anywhere at any time.

Out of phase: relevance of the medial septum for directional hearing and phonotaxis in the natural habitat of field crickets

  • Stefan HirtenlehnerAffiliated withDepartment of Zoology, Karl-Franzens-University
  • , Heiner RömerAffiliated withDepartment of Zoology, Karl-Franzens-University
  • , Arne K. D. SchmidtAffiliated withDepartment of Zoology, Karl-Franzens-University Email author 


A modified tracheal system is the anatomical basis for a pressure difference receiver in field crickets, where sound has access to the inner and outer side of the tympanum of the ear in the forelegs. A thin septum in the midline of a connecting trachea coupling both ears is regarded to be important in producing frequency-dependent interaural intensity differences (IIDs) for sound localization. However, the fundamental role of the septum in directional hearing has recently been challenged by the finding that the localization ability is ensured even with a perforated septum, at least under controlled laboratory conditions. Here, we investigated the influence of the medial septum on phonotaxis of female Gryllus bimaculatus under natural conditions. Surprisingly, even with a perforated septum, females reliably tracked a male calling song in the field. Although reduced by 5.2 dB, IIDs still averaged at 7.9 dB and provided a reliable proximate basis for the observed behavioural performance of operated females in the field. In contrast, in the closely related species Gryllus campestris the same septum perforation caused a dramatic decline in IIDs over all frequencies tested. We discuss this discrepancy with respect to a difference in the phenotype of their tracheal systems.


Directional hearing Cricket Acoustic tracheal system Sound localization Pressure difference receiver