The compound eyes of insects typically exhibit hexagonal packing schemes. This can be clearly seen in
some of the examples here.
No doubt the same criteria of maximising light-sensitive area coverage while
minimising the volume of inert edge-cell material that are familiar from honeycombs apply here.
Nature may also have had some other design criteria in mind:
- Hexagonal cells have the shallowest sharp corners of any regular tesselating
shape - this may mean that cells can be built with the minimum internal
reinforcing at their corners.
- Hexagonal packing schemes mean that each cell has the maximum numbers of
close neighbours, and the maximum rotational and reflectional symmetries. These
properties may be important when linking several cells together to form
edge-detector and motion-detector cell clusters.