STIMULUS DISCRIMINATION AND WAVE SOURCE LOCALIZATION IN FISHING SPIDERS (DOLOMEDES TRITON AND D-OKEFINOKENSIS)

We have studied the behavioral responses of fishing spiders (Dolomedes triton and Dolomedes okefinokensis) to water surface wave stimuli. D. okefinokensis responded to click-like wave stimuli (Fig. 3C) in less than 15% of the cases. Responsiveness did not increase if up to 20 cli cks were elicited in quick succession from the same spot (Fig. 5). If longer lasting concentric stimuli were offered, the spiders determined the direction (Fig. 6) and the distance (Fig. 8) to the wave source. This was true for monofrequency stimuli and for narrow-band and broadb and noise stimuli. If concentric multifrequency surface waves were off ered, even a fivefold decrease in stimulus amplitude did not significa ntly change the mean running distance of D. triton. However, if multif requency wave stimuli with a flat wave front were presented, the spide rs (D. triton) no longer determined the source distance precisely (Fig s. 11, 12). Our results indicate that fishing spiders of the genus Dol omedes mainly use the curvature of a concentric wave stimulus for dist ance determination.