SPRAYBERRY, J. D. H.*; DANIEL, T.; Univ. Washington, Seattle; Univ. Washington, Seattle: Control of left-right steering in Manduca sexta

Motor behaviors are influenced by the properties and constraints of the mechanical systems in which they operate. Hawkmoths feeding from moving flowers exhibit a visually guided tracking behavior. Given the visual stimulus of a flower oscillating left and right, we would expect a feeding hawkmoth to also fly left and right. Hawkmoths, like other lepidopterans, have an indirect flight mechanism in which two sets of power muscles (the dorsolongitudinals and the dorsoventrals) move the wings up and down by deforming the thorax. Subtle changes in wing kinematics, which are largely responsible for maneuvering, are controlled by steering muscles that alter the mechanical behavior of the thorax and wing hinge. These steering muscles consist of three functional groups: the axillary, basalar, and subalar muscles. We used EMG recordings from tethered Manduca sexta subjected to left-right visual motion stimuli to investigate the role of the subalar steering muscles in maneuvering flight. The subalar muscles demonstrate small but significant phase shifts in average timing of activation (1.1-6.2%) correlated with changes in horizontal motion. These phase shifts are very consistent within individuals, but the direction of phase shift varies between individuals. However, multiple motor forcing functions could result in similar cuticular deformations that are required for appropriate changes in wing kinematics. Our results indicate that the subalar steering muscles are likely involved in, but not the sole controllers of, left-right maneuvering.