Auditory behavior of the cricket

Summary

• 1. Many one-eared female crickets (Gryllus campestris andGryllus bimaculatus), whether the loss is due to surgery or to developmental accident, can maintain characteristic, stable courses with respect to the direction of male calling song, when tested on the Kramer spherical tread-mill. The error angles are usually less than 90°, so that Regen's (1924) remark about the success of such females in finding singing males is supported.

• 2. Some females with developmental unilateral hearing deficit, confirmed both histologically and by sparing of tracking after removal of the suspect leg, track nearly as accurately as normal animals with two ears.

• 3. Experiments in which tympana were immobilized with wax, whether tracking behavior or interneuron responses were monitored, show that the anterior tympanum — considered for some time to be irrelevant to hearing — mediates appreciable sound input to the auditory receptors, at least when the posterior tympana are blocked.

• 4. The above results resolve two current paradoxes regarding comparison of tympanum immobilization in behavior with the mechanics of receptor excitation:

  First, because even unambiguously one-eared animals can maintain stable sound-oriented courses, such tracking performance with waxed tympana does not argue that total tympanal immobilization spares some auditory function of that ear (cf. Schmitz et al. 1983). The argument assumes that tracking would not be expected if one ear were silenced; the assumption is evidently false.

  Second, it has been unclear why waxing of both posterior tympana raises tracking threshold only ca. 20 dB (Schmitz 1983) whereas the tympanalmechanics studies of Kleindienst et al. (1983) have suggested a much greater deficit. Our finding that one must wax the anterior tympana as well, in order to produce deficit greater than ca. 20 dB, clarifies the situation. That is, in the biophysical experiments both tympana of the leg were immobilized by the procedures used (pressure matching and water immersion), whereas in most current behavioral tympanum-waxing experiments (but not in those of Bailey and Thomson 1977) the anterior tympana have been ignored.

• 5. A novel behavioral effect was observed with all four tympana blocked. Thresholds for orientation were ca. 90–100 dB, but in every case the animals tended to walk away from the loudspeaker.

• 6. The search for an explanation of one-eared tracking leads us to analogies with the recovery from imbalance following such surgery as hemilabyrinthectomy in vertebrates. A ‘phantom tympanum’, on the side with deficit, could in principle participate in corrective tracking, by the usual notions of bilateral comparison.