Control of the horizontal flight-course by air-current sense organs in Locusta migratoria

ABSTRACT. The role of the air-current sense organs of Locusta migratoria (the antennae and the hair fields on the frons and vertex of the head) in control of the horizontal flight-course in relation to the air was investigated in locusts flying tethered on a torque gauge. The antennae were apparently not of importance in the control of flight direction in the horizontal plane. If the hair fields were stimulated by an air current from either side, however, a torque on the vertical body axis was generated by the beating wings after a reaction time of at least 0.1 s. In free flight this would result in a yaw, bringing the animal back in line with the air stream. This torque reaction will stabilize the flight direction in the horizontal plane via a negative feedback mechanism, the hair fields above the lateral ocelli being the feedback receptors. In free flying locusts a torque on the vertical body axis can be generated by both the beating wings and the abdomen working as a rudder when bent to either side. The wings, however, are dominant in the reflex stabilization of the flight-course.