How Many Eyes Does a Fly Have?
The head of a fly is almost “all eyes.” Most flies have four eyes—two large compound eyes and two tiny simple ones called “ocelli.” But the housefly has five eyes! Each of a fly’s enormous compound eyes is made up of 4,000 small lenses.
Everything a fly looks at appears as thousands of tiny images. In addition to its big eyes, there are those tiny ones on top of the fly’s head. Most flies have just two of these ocelli. The housefly has three, making a total of five eyes.
They are set in a triangle between the pair of big compound eyes. Since they are slightly domed, he gets a view from several directions at once. With its many eyes watching, a wide awake fly is usually able to dodge your swatter safely.