Meeting Abstract
Like many synchronous and asynchronous flying insects, steady flight in Manduca sexta typically occurs in a narrow band of wingbeat frequencies. However context can modulate this range. Artificial reduction of wing inertia causes a compensatory increase in wingbeat frequency of roughly 10%. Similarly, load lifting experiments increased wingbeat frequency by 20%. These results highlight the capacity for Manduca sexta to change wingbeat frequency to compensate for steady state changes in flight requirements. We hypothesize that Manduca sexta might also utilize rapid wingbeat frequency modulation to recover from large transient perturbations. To address this hypothesis, we recorded high speed video of hawkmoth flight at 2000 fps (n = 7). After each moth established stable hovering to feed in front of an artificial flower, we perturbed their flight by shooting the moths laterally with vortex rings. We estimated instantenous phase and wingbeat frequency via a Hilbert transformation on wing kinematics. Prior to the perturbation, the moths had an average wingbeat frequency of 24.7 +/- 1.4 Hz. In comparison, average wingbeat frequency over ten wingbeats during perturbation and recovery was 21.5 +/- 6.4 Hz. Although we found no change in mean wingbeat frequency (p = 0.25), there was a substantial increase in wingbeat frequency modulation. Pre perturbation, the frequency range was 2.6 +/- 1.0 Hz, which increased to 16.2 +/- 3.9 Hz post perturbation (p < 0.01). This range corresponds to roughly 65% of average wingbeat frequency. Furthermore, EMG recordings of the downstroke flight muscles corroborate that changes in wingbeat frequency are driven by changes in neural stimulation rate . These results suggest that synchronous flying insects may have wide control affordance in frequency when challenged with extreme conditions.
