Abstract

Male field crickets generate calls to attract distant females through tegminal stridulation: the
rubbing together of the overlying right wing which bears a file of cuticular teeth against the
underlying left wing which carries a sclerotised scraper. During stridulation, specialised areas of
membrane on both wings are set into oscillating vibrations to produce acoustic radiation. The
location of females is unknown to the calling males and thus increasing effective signal range in all
directions will maximise transmission effectiveness. However, producing an omnidirectional sound
field of high sound pressure levels may be problematic due to the mechanical asymmetry found in
this sound generation system. Mechanical asymmetry occurs by the right wing coming to partially
cover the left wing during the closing stroke phase of stridulation. As such, it is hypothesised that the
sound field on the left-wing side of the animal will contain lower sound pressure components than
on the right-wing side as a result of this coverage. This hypothesis was tested using a novel method
to accurately record a high resolution, three dimensional mapping of sound pressure levels around
restrained Gryllus bimaculatus field crickets singing under pharmacological stimulation. The results
indicate that a bilateral asymmetry is present across individuals, with greater amplitude components
present in the right wing side of the animal. Individual variation in sound pressure to either the right
or left-wing side is also observed. However, statistically significant differences in bilateral sound field
asymmetry as presented here may not affect signalling in the field.