The Vertical Migration of Infective Larvae of Strongyloid Nematodes

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Abstract
Using a technique to reduce the possibility of establishing gradients of temperature, illumination, etc., it has been shown that infective larvae of T. retortaeformis, sheep trichostrongyles and horse trichonemes move in random directions when on a vertical plane at temperatures of 16°–17°C. and at 27°C.In a horizontal plane the same randomness was shown.Larvae moving in channels of different widths moved different distances along the channels in the same time. In narrow channels the distance moved was approximately proportional to the time (T) of movement. In wide channels the distance was approximately proportional to ✓T.The effect of a drying water film on the movements of larvae of T. retortaeformis are described.It is concluded that vertical migration of the larvae may be described in terms of normal larval movements without reference to geotropism or undescribed special receptors in the larvae.