Kinematic and aerodynamic aspects of ultrasound-induced negative phonotaxis in flying Australian field crickets (Teleogryllus oceanicus)

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Abstract
Negative phonotaxis is elicited in flying Australian field crickets,Teleogryllus oceanicus, by ultrasonic stimuli. Using upright tethered flying crickets, we quantitatively examined several kinematic and aerodynamic factors which accompany ultrasound-induced negative phonotactic behavior. These factors included three kinematic effects (hindwing wingbeat frequency, hindwing elevation and depression, and forewing tilt) and two aerodynamic effects (pitch and roll). Within two cycles following a 20 dB suprathreshold ultrasonic stimulus, the hindwing wingbeat frequency increases by 3–4 Hz and outlasts the duration of the stimulus. Moreover, the relationship between the maximum increase in wingbeat frequency and stimulus intensity is a twostage response. At lower suprathreshold intensities the maximum wingbeat frequency increases by approximately 1 Hz; but, at higher intensities, the maximum increase is 3–4 Hz. The maximum hindwing elevation angle increases on the side ipsilateral to the stimulus, while there was no change in upstroke elevation on the side contralateral to the stimulus. An ultrasonic stimulus affects forewing tilt such that the forewings bank into the turn. The forewing ipsilateral to the stimulus tilts upward while the contralateral forewing tilts downward. Both the ipsilateral and contralateral forewing tilt change linearly with stimulus intensity. Flying crickets pitch downward when presented with a laterally located ultrasonic stimulus. Amputation experiments indicate that both the fore and hindwings contribute to changes in pitch but the pitch response in an intact cricket exceeds the simple addition of fore and hindwing contributions. With the speaker placed above or below the flying cricket, the change is downward or upward, respectively. For all cases, the magnitude of the pitch change is linearly related to stimulus intensity. Ultrasound induces flying crickets to roll away from the stimulus source location. The dynamics of the changes in roll are similar to the changes in pitch. That is, the change in roll is a function of both wing pairs and the magnitude is stimulus intensity dependent. Thus ultrasound-induced negative phonotaxis in flying crickets is a complex behavior involving several kinematic and aerodynamic changes. This behavioral complexity lends further credence to the hypothesis that cricket negative phonotaxis provides a valuable function, perhaps as a bat avoidance response.