Like other insects, flies have compound eyes that are made up of thousands of smaller faceted eyes. Insects don't see one image per facet, they see objects in a distorted, somewhat blurred view. They are very sensitive to movement however, that's why it's so hard to swat a fly! It is interesting how the compound eyes refract the light into many different colors on some insects! This Deer Fly is probably a male, due to the fact the eyes nearly meet a the center of the head.