Bilateral symmetry of sound production in the mole cricket, Gryllotalpa australis

Abstract

1. Males of the mole cricket, Gryllotalpa austrails (Orthoptera, Gryllotalpidae), produce their calling song from a specially constructed burrow, which has four horn-shaped openings at the surface of the soil. 2. Males will also call from an artificial burrow with dimensions similar to the natural burrow, making it possible to study their wing movements during singing in the laboratory (Fig. 3). 3. The calling song of G. australis is a continuous train of sound pulses with a mean frequency of 2.5 kHz (Fig. 4). The mean pulse repetition rate at 23°C is 70 Hz. Calling songs produced in the artificial burrows are similar to those produced in natural burrows. 4. More than half the males studied in the artificial burrows sang with forewings arranged both right-overleft and left-over-right. Usually, males kept to one or other arrangement for the duration of a given calling song, but some males showed a propensity for changing wing arrangement during the song (Fig. 6). 5. There was no significant difference between calling songs produced with the wings arranged right-over-left and those with the wings left-over-right, with respect to all major parameters including intensity (Fig. 5). 6. The file and scraper structures are equally well developed on both left and right forewings of male G. australis (Fig. 7). The forewings lack the conspicuous group of sensory hairs that function to prevent a change of wing arrangement in field crickets. 7. We conclude that mole crickets normally use both right-over-left and left-over-right wing arrangements in singing and that both are equally efficient at producing sound.