How many eyes do most spiders have?

Most spiders have eight eyes. These eyes are simple eyes, each with a single lens, rather than the compound eyes found in insects. They are usually arranged in two rows of four on the front part of the cephalothorax, and their positions help scientists identify spider families and species.

Eight eyes does not mean eight equally useful eyes. In many spiders, the eyes mainly detect brightness and movement, while vibrations through webs and surfaces provide more important information. Jumping spiders are an impressive exception: their large front eyes provide unusually sharp vision, and some species can distinguish colors and estimate distance while hunting.

The number varies widely among spiders. Many haplogyne spiders have six eyes, some caponiid spiders have only two, and certain cave-dwelling species have lost their eyes entirely. A common mix-up is confusing eyes with ocelli: spider eyes are often called ocelli because they are single-lens eyes, but they are still functional visual organs.