52.4 Thursday, Jan. 5 The control of saccades in hoverflies WALKER, SM*; TAYLOR, GK; University of Oxford, UK; University of Oxford, UK email@example.com
Saccades are fast turning manoeuvres, characteristic of dipteran flight. The wing kinematic parameters controlling these rapid turns have been investigated for several species, with changes in stroke amplitude and angle of attack being principal contributors to the generation of the required torques. However, the precise changes in wing kinematics that are used to control the duration and total angular displacement of saccades are not well known. We used high-speed digital video of free-flying hoverflies (Eristalis tenax and Eristalis pertinax) and automated tracking to reconstruct the body and wing kinematics of insects performing spontaneous saccades. We recorded more than 250 saccades, with angular displacements ranging from 10° to 115°. The total angular displacement is proportional to the maximum angular acceleration of the body, suggesting that Eristalis adjust the torque produced by asymmetries in the left and right wings to control turns rather than applying a constant torque and modulating its duration. We measured wing kinematic parameters, calculated separately on each downstroke and upstroke, and fitted them to an analytical model to test their association with the body’s angular accelerations. A range of kinematics parameters contribute to the control of saccades, with stroke amplitude and angle of attack being important, but also the timing of wing rotation and the stroke plane angle. During the second half of saccades, when the body decelerates, there is an asymmetry in the kinematics of the wings of opposite sign to that used in the first half of the turn. These reverse asymmetries are of similar magnitude to those used in the acceleration phase indicating that active production of a counter-torque is the main method used to terminate saccades, rather than a passive flapping counter-torque.