Resonance in herbaceous plant stems as a factor in vibrational communication of pentatomid bugs (Heteroptera: Pentatomidae)

Pentatomid bugs communicate using substrate-borne vibrational signals that are transmitted along herbaceous plant stems in the form of bending waves with a regular pattern of minimal and maximal amplitude values with distance. We tested the prediction that amplitude variation is caused by resonance, by measuring amplitude profiles of different vibrational pulses transmitted along the stem of a Cyperus alternifolius plant, and comparing their patterns with calculated spatial profiles of corresponding eigenfrequencies of a model system. The measured distance between nodes of the amplitude pattern for pulses with different frequencies matches the calculated values, confirming the prediction that resonance is indeed the cause of amplitude variation in the studied system. This confirmation is supported by the resonance profile obtained by a frequency sweep, which matches theoretical predictions of the eigenfrequencies of the studied system. Signal bandwidth influences the amount of amplitude variation. The effect of both parameters on signal propagation is discussed in the context of insect vibrational communication.