Meeting Abstract
Flies rely heavily on retinal image motion to control their flight speed. In the presence of changes in wind speed or background visual motion, they are able to uphold a consistent retinal image velocity within their locomotor constraints by varying their airspeed. Flies regulate flight speed primarily by adjusting their body pitch – a mechanism frequently characterized as helicopter model. However, it is unknown whether the flies are able to regulate their speed via only the modulation of wing kinematics in the absence of pitch maneuver, or to what extent the visual control can regulate speed under this locomotor constraint. In this study, we investigated the visual speed control of blue bottle flies (Calliphora vomitoria) flying at zero body pitch in a magnetically-levitated flight mill, with motorized cylindrical walls displaying grating patterns. We perturbed the flies’ retinal image motion via spinning the grating patterns of different spatial frequencies (22, 11, and 0 1/rev) at different angular velocities. Results showed that at a fixed body pitch flies were able to compensate the image-motion perturbation by adjusting their airspeed up to 20%, thereby to maintain the retinal image velocity relatively constant (0.47+/-0.03 rad/s). However, the compensation weakened as their airspeed plateaued when the image-motion perturbation became large, indicating that flies were unable to further increase or decrease their speed due to locomotor constraint. The compensation gain, i.e., the ratio of airspeed changes and image-motion perturbation, was largest at the intermediate spatial frequency.
