Fast and slow flight torque responses in flies and their possible role in visual orientation behaviour

Abstract

The flight torque responses of tethered flying houseflies to motion and presentation or removal of a vertical dark stripe on a bright background were recorded in real time. Motion with constant speed of 100° s-1 from front to back elicits a strong fast response following the diraction of the stimulus motion. Motion from back to front elicits a weaker response. Instantaneous presentation and removal of a stationary stripe elicit weak, slow response. Apparent motion from front to back and from back to front elicit weak responses with a fast, directionally selective, transient peak followed by a slow response component oriented towards the stripes position. The fast transient peak response is not elicited if the animals were stimulated before with real movement of the stripe. The results are discussed and an earlier proposed model for free flight tracking and fixation is extended.