Insects which turn and look

Abstract

The compound eyes of insects and crustaceans are not uniform: regions which look in different directions become specialized for different functions. Some regions have larger facets and smaller angles between adjacent visual axes. Larger facets allow greater resolution for individual ommatidia of the eye; smaller angles between their axes allow a greater density of sampling stations. Many insects have one or more foveas, together with specialized visual habits, but even without a fovea, turning to look is probably a basic part of insect behaviour. Accurate alignment of the head axis then allows the estimation of distance without necessity for stereopsis. The form of the eye in many insects strongly suggests that they measure range over long distances by parallax rather than by binocular overlap.