Do bugs really have a thousand eyes?
(Lansing State Journal, November 25, 1992)
Most insects have what are called compound eyes. This means that instead of using a single set of lenses to form an image, as do humans, there are many sets of lenses. Although these sets of lenses do indeed look like thousands of tiny eyes, they do not each form a separate image. Instead the lenses work together to form a single image. This means that when a fly sees a swatter coming at it, it sees a single fly swatter, not hundreds or thousands.
The eyes of most insects do a very poor job of creating an image. A fruit fly would need to be closer than three centimeters from another fruit fly before it would look like anything more than a small blob.