Factors that possibly influence variation in the calling song of field crickets: temperature, time, and male size, age, and wing morphology

Abstract

The structure of the calling song of the Texas field cricket, Gryllus integer, was studied. Pulse rates, percentage of missed pulses within a trill, numbers of pulses per trill or trill lengths, and intertrill intervals were measured for males singing in the field and in the laboratory. All song parameters were variable and were distributed normally. Intertrill intervals were longer in the laboratory, but all other parameters were similar in laboratory and field populations. Pulse rates varied in a linear fashion with ambient temperature in the laboratory and field. The percentage of missed pulses in a trill decreased with increasing temperature in the field and in the laboratory; intertrill intervals varied inversely with temperature only in the field. In field populations, immediately before and after sunrise male songs had fewer pulses per trill and a greater frequency of missed pulses than songs produced for a few hours following sunset. Song structure did not vary with age, weight, or hind-wing dimorphism. Most song parameters were correlated with each other. The data are discussed in terms of female choice and attraction to male song, male competition by way of acoustical interaction, and underlying genetic variation in G. integer.