Visual deprivation and distance estimation in the praying mantis larva

Abstract. Young larvae of the praying mantis, Tenodera sinensis Saussure, were placed on an off-centre island surrounded by a round arena with six black bars painted on a white inner wall. In this situation, it was shown that the horizontal peering movements of the head often seen in mantids are in fact used to measure distances; motion parallax may be involved in this process. Aimed jumps that followed peering were taken to be the distinct result of an absolute distance measurement. Specific visual deprivation such as painting over of certain parts of the eye with opaque black varnish or degeneration of the fovea with sulforhodamine showed that: absolute evaluation of distance is only possible with two fully intact eyes; the peering mechanism is under visual control; and visual experience has a long-term effect on distance measurement involving peering movements.