Fig. 3. Modelling damping coefficient in Drosophila. (A) During yaw turning, stroke amplitude changes due to an active component (_A) caused by the fly's steering muscles, and passive changes (_P) due to body rotation. Note the different contribution of passive components during the stroke cycle (downstroke, top; upstroke, bottom). (B) Turning rate of a fruit fly in response to the impulsive start of yaw torque. Data were modelled at different frictional damping coefficients, at a constant torque of 0.29 pNm, and 0.52 pNm s² moment of inertia. Numbers in parentheses (1–8) correspond to damping coefficients 52, 156, 208, 260, 520, 1040, 2080 and 5200 pNm s, respectively. The shaded area indicates the maximum threshold range for visual motion detection (cf. Fig. 1E).