The effect of noise on sexual behaviour of the southern green stink bug Nezara viridula

Stink bugs of the pentatomid family communicate using substrate-borne vibrational signals transmitted through host plants. Specific signal length and repetition rate are critical for mate recognition and are susceptible to masking by simultaneous conspecific and congeneric signals. We tested whether overlapping conspecific signals interrupt Nezara viridula (L.) sexual behaviour with playback of continuous vibration (disturbance). The disturbance decreased the number of males responding to simultaneously presented female signals, but it did not influence the time they needed to find the source of female signals. N. viridula females proceeded with mate calling during disturbance playback, but most of them paused for one or more signal intervals and/or emitted socalled repelling signals. The proportion of females that changed the dominant frequency of their calls decreased with increasing difference between the dominant frequency of the disturbance signals and the emitted female calling song. There was no equivalent change in other call parameters, or in the proportion of females that changed rhythm or song type. This indicates that female calling frequency shift is the main method of reducing the effect of signal masking in N. viridula vibrational communication.