How is the vision of insects and arachnids different?

Most Spiders have four pairs of simple eyes, usually grouped into two or three rows, an arrangement that gives them a wide field of vision. Insects have one pair of compound eyes, each made up of individual hexagonal-shaped facets and each facet has its own optic nerve. Their compound eyes allow them to see all around themselves without moving, and this ability makes them very sensitive to seeing any nearby movement.