Orientation to Calling Song by Female Crickets, Scapsipedus Marginatus (Gryllidae)

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Abstract
Video-tape recordings of the orientation behaviour of female crickets Scapsipedus marginatus in response to the calling song of conspecific males demonstrate that turning and locomotion of the animal toward a target are determined by the sensory information received before the movement is initiated and are unaffected by auditory input received during movement, i.e. the control system is an open-loop type. Sound location comes about through the animals’ ability to turn toward the sound source. The probability of turning in the correct direction is maximal when the sound source lies in the lateral quadrant with respect to the longitudinal body axis, and it is symmetric about the perpendicular to the body axis. The correlation between the angle of the turning response and that of the direction of the sound stimulus is very small. Animals tend to make smaller turns when the target angle is less than 60° than when it is greater than 6o°. Sound which is incident from the posterior direction elicits larger turns than sound which is incident from the anterior direction. Thus, the cricket can tell whether sound is coming from the forward or backward direction and respond accordingly. One-eared animals usually turn toward the intact ear in response to auditory stimulation. The orientation behaviour therefore depends on a comparison of stimuli incident at the two ears. This result contradicts the findings of Regen who claims that one-eared animals can locate a sound source. The leg movements demonstrated by video close-ups of single turns show varying patterns. The pattern postulated by Autrum, however, is not among these.