Spatial vision in the course of an insect's life.

Praying mantises are considered to be phylogenetically ancient insects with their roots in the palaeozoic Protoblattoidea. They have evolved two mechanisms for spatial vision: (a) estimating the distance to moving prey objects with the use of binocular disparity [Rossel, 1983] and (b) estimating the distance to stationary target objects with motion parallax produced by head movements [Poteser and Kral, 1995]. There is no doubt that the ability to use both visual cues is congenital, but the degree to which either mechanism is developed and its significance to the individual depends to some extent upon the animal's age and exposure to prey species and environmental cues. Experience and learning play an important role. It appears that young mantises can perform both binocular and monocular calculations of distance but they grow to depend more on the binocular mechanism. Motion parallax plays an important role in movement strategy throughout the course of a mantis's life, but this mechanism appears to be particularly in early life.