Compound eye of a Cuckoo’s Wasp (Chrysis ignita). Eyes are generally adapted to the environment and life requirements of the organism which bears them. For instance, the distribution of photoreceptors tends to match the area in which the highest acuity is required, with horizon-scanning organisms, such as those that live on the African plains, having a horizontal line of high-density ganglia, while tree-dwelling creatures which require good all-round vision tend to have a symmetrical distribution of ganglia, with acuity decreasing outwards from the centre.
However, it is not only the shape of the eye that may be affected by lifestyle. Eyes can be the most visible parts of organisms, and this can act as a pressure on organisms to have more transparent eyes at the cost of function. Eyes may be mounted on stalks to provide better all-round vision, by lifting them above an organism’s carapace; this also allows them to track predators or prey without moving the head. The Cuckoo’s Wasps are excellent flyers and have very efficient eyes with plenty of densely packed single lenses.