Kinematics of phonotactic steering in the walking cricket Gryllus bimaculatus (de Geer)

Female crickets, Gryllus bimaculatus, are attracted by the male calling song and approach singing males; a behaviour known as phonotaxis. Even tethered females walking on a trackball steer towards a computer-generated male song presented from their left or right side. High-speed video analysis showed how this auditory-evoked steering was integrated with walking. Typically all the front and middle legs showed kinematic adjustments during steering, with the trajectories tilted towards the side of acoustic stimulation. Furthermore, the average speed of the tarsi contralateral to song increased relative to the ipsilateral tarsi. Kinematic changes of the hind legs were small and may be a consequence of the front and middle leg adjustments. Although phonotactic steering generally led to stereotyped adjustments there were differences in the specific combination of kinematic changes in leg trajectories. The most reliable kinematic steering response was by the contralateral front leg, such that, during its swing phase the tarsus moved towards the side of acoustic stimulation through an increased forward rotation of the femur and an increased extension of the tibia. Relating the changes in tarsal positioning of each leg to the steering velocity of the animal indicated that typically the front and middle legs contralateral to song generated the turning forces. Phonotactic steering was integrated into forward walking without changes to the walking motor cycle.