Drift compensation and its sensory basis in waterstriders (Gerris paludum F.)

Summary Watestriders (Gerris paludum F.), displaced by flowing water or wind, compensate for this by periodic jumps against the direction of drift so that they keep their average position — relative to the river bank, for instance — constant over long periods of time. To identify the cues used by the animals to compensate for drift, they were kept on an artificial stream with visual patterns along one or both sides. The velocity of the water flow and the pattern motion were varied. It is not possible to induce compensatory jumps in darkness by water or air current alone. Visual cues are indispensable for the reaction. The product of jump amplitude and jump frequency equals the drift velocity on average. The jump amplitudes are more or less independent of the flow velocity while the jump frequency is adjusted to it.