Vibrational communication along plants by the stink bugs Nezara viridula and Murgantia histrionica

The velocity and spectral characteristics of vibrational signals of Nezara viridula (L.) and Murgantia histrionica (Hahn) (Heteroptera: Pentatomidae) were analyzed as the signals were transmitted through different plants. The velocity parameter of the body vibrations ranges from 0.1 to 1 mm/s. According to the mechanical properties of different substrates, the signal is attenuated or amplified during transmission from the insect's body to the substrate. Attenuation of up to 20 dB occurs during transmission of signals from leaves to stalks or stems. The velocity decrease with distance is below 0.5 dB/cm during transmission through less dense green stems, whereas it ranges between 0.6 and 1.6 dB/cm during transmission through more dense, woody stems. Signal velocity decreases non-linearly with increasing distance from the signal source. Regularly repeated velocity minima (nodes) and maxima (internodes) spaced 10–15 cm apart are characteristic of signal transmission through green plants but not woody stems. The signal velocity at some internodes exceeds the input value for N. viridula but not M. histrionica signals. The relative amplitude of the dominant frequency spectral peak varies with distance, along with overall signal velocity. Variable ratios of spectral peak amplitudes are characteristic for signals recorded at different distances from the source.