Abstract

Male field crickets (Orthoptera: Gryllidae) produce acoustic signals by wing stridulation, attracting females for mating. A plectrum on the left forewing’s (or tegmen) anal margin rapidly strikes along a serrated vein (stridulatory file) on the opposite tegmen as they close, producing vibrations ending in a tonal sound. The tooth strike rate of the plectrum across file teeth is equal to the sound frequency produced by the cricket (i.e., ~5k teeth/s for ~5 kHz in field crickets) and is specific to the forewing’s resonant frequency. It is subsequently amplified using specialised wing cells. Anatomically, the forewings appear to mirror each other: a file and plectrum exist on both tegmina; however, most cricket species stridulate using right-over-left wing overlap making the stridulatory mechanism directionally asymmetrical by default, rendering the left tegmen’s file unused. Therefore, we hypothesise structural differences between the functional and unfunctional files. Three-dimensional images were used to accurately measure the stridulatory file structure in Gryllus bimaculatus wings. It was found that the left file shows significantly greater variation in inter-tooth distance than the right file, both over the entire file and especially the first sixty teeth (the functional part). Advantages of this modern method over scanning electron microscopy are discussed.