Figure 1. Examples of field cricket courtship songs. Oscillograms of stereotypical, loud high-amplitude ‘ticks’ and softer lower-amplitude ‘chirps’ of (a) Gryllus texensis and (b) G. ovisopis. (c) Oscillogram of courtship song of Teleogryllus oceanicus showing stereotypical high-amplitude ‘chirps’, followed by lower-amplitude pulses, which make up the ‘trill’. These examples are not indicative of the relative differences in absolute amplitude between these MLN0128 individuals or species. (a) Entire recording available at http://macaulaylibrary.org/audio/130070. Recording made by T. J. Walker, Arkansas, August 1973. (b) Entire recording available at http://macaulaylibrary.org/audio/129871. Recording made by T. J. Walker, Florida, September 1972. (c) Entire recording available upon request. Recording made by S. L. Balenger, Minnesota, March 2013.Figure optionsDownload full-size imageDownload as PowerPoint slide
In a study designed to evaluate whether courtship song might be involved in reproductive isolation between the cryptic sister species G. texensis and Gryllus rubens, Fitzpatrick and Gray (2001) found that amplitude was the same on average (79.8 dB at 19 cm) for the high-frequency ticks, but significantly different between the two species for the low-frequency chirps (65.9 dB for G. texensis, 71.9 dB for G. rubens at 19 cm). The within-species CV for the amplitudes of both ticks and chirps were relatively low (4.4–8.2%), but it remains unclear whether amplitude in this case would be more likely to indicate species identity than male quality because there was no information regarding within-male variability. Subsequent studies of these two species have evaluated both within-species and within-individual song properties, but have focused on calling song and ignored amplitude ( Higgins & Waugaman, 2004).