Specificity of the calling song and short term changes in the phonotactic response by female cricketsScapsipedus marginatus (Gryllidae)

Summary

• 1. The calling song of the male cricket Scapsipedus marginatus consists of a long series of chirps. Each chirp consists of 4–6 sound pulses separated by alternating shorter and longer intervals (Fig. 3). The dominant frequency of the song is approximately 5 kHz (Fig. 6) and the chirp interval is 1.6 sec (Fig. 4).

• 2. As measured by the ability of conspecific females to locate the sound source when they are allowed to respond by freely walking, the pulse interval pattern is the only species-specific characteristic of theS. marginatus calling song. The other characteristics of the song-chirp interval, fundamental frequency, number of pulses per chirp-may be severely altered without affecting the phonotactic response, e.g. the phonotactic response is elicited by an artificial song with the specific pulse pattern but with fundamental frequency of 18 kHz (Fig. 7).

• 3. The phonotactic response to continuous stimulation by natural calling song is characterized by short-term changes: an initial period of arousal followed by a highly active steady state which declines after a short period (Fig. 11).

• 4. A non-specific stimulus, the calling song of a sympatric species will elicit locomotion in female crickets. The initial incremental period before locomotion begins is significantly greater than that which occurs when the stimulus is the species-specific calling song (Fig. 12).

• 5. Although motor output (walking) can be driven by non-specific acoustical stimuli, the species-specific sensory input is required for locomotion to be directed to the sound source.