Tooth impact rate in the song of a shorthorned grasshopper: A parameter carrying specific behavioral information

Summary Receptive females of the gomphocerine grasshopperOmocestus viridulus L. were offered different artificial grasshopper songs in a one- or two-channel test situation. In the computer generated songs the tooth-impact-rate and the amplitude functions of the chirp were varied.The results of the one-channel experiments showed that the grasshoppers preferred signals with normal tooth-impact-rate to signals with half the rate. The amplitude function seems to play a minor role in the recognition process, unless this parameter is changed very radically.The results of the two-channel tests were ambiguous. A third test series was developed to interpret these results. It was found that female grasshoppers once excited by an acceptable signal afterwards responded to former unacceptable signals. Accordingly, if just one of the two signals is able to excite the female, the female may subsequently choose randomly between the signals. If the signals are of different sound levels, the louder is preferred.The shorthorned grasshopper may interpret the tooth-impact-rate as a frequency. It is proposed that the grasshopper may use the four sense cell groups of the ear as a simple sort of a spectral analyzer. These cells are tuned to different frequencies and/or differently tuned.The running Root Mean Square value of a grasshopper signal, its dependence on the applied integration time and its possible relation to perceived energy are reported in an appendix.