Moving animals orchestrate myriad motor systems in response to multimodal sensory inputs. Coordinating movement is particularly challenging in flight control, where animals deal with potential instability and multiple degrees of freedom of movement. Prior studies have focused on wings as the primary flight control structures, for which changes in angle of attack or shape are used to modulate lift and drag forces. However, other actuators that may impact flight performance are reflexively activated during flight. We investigated the visual–abdominal reflex displayed by the hawkmoth Manduca sexta to determine its role in flight control. We measured the open-loop stimulus–response characteristics (measured as a transfer function) between the visual stimulus and abdominal response in tethered moths. The transfer function reveals a 41 ms delay and a high-pass filter behavior with a pass band starting at ~0.5 Hz. We also developed a simplified mathematical model of hovering flight wherein articulation of the thoracic–abdominal joint redirects an average lift force provided by the wings. We show that control of the joint, subject to a high-pass filter, is sufficient to maintain stable hovering, but with a slim stability margin. Our experiments and models suggest a novel mechanism by which articulation of the body or ‘airframe’ of an animal can be used to redirect lift forces for effective flight control. Furthermore, the small stability margin may increase flight agility by easing the transition from stable flight to a more maneuverable, unstable regime.
J.P.D., T.L.D. and N.J.C. conceived and and designed the experiments. J.P.D. performed the behavioral experiments. J.P.D. and N.J.C. developed the model and performed the analyses. J.P.D., T.L.D. and N.J.C. interpreted the results. J.P.D., K.A.M., T.L.D. and N.J.C. wrote the paper.
Supplementary material available online at http://jeb.biologists.org/cgi/content/full/216/9/1523/DC1
No competing interests declared.
This material is based upon work supported by the National Science Foundation under a Postdoctoral Research Fellowship in Biology [no. 1103768 to J.P.D.] and grant nos EEC-1028725 (to T.L.D.) and CISE-0845749 (to N.J.C.); the Office of Naval Research under grant no. N000141010952 (to K.A.M. and T.L.D.); the Air Force Research Laboratory as part of the DARPA HI-MEMS program (T.L.D. and J. Voldman); and a Komen Endowed Chair to T.L.D.
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