How Many Eyes Does a Spider Have?
Most spiders have eight simple eyes. The two main eyes of a spider each have a simple lens, and a retina which is made up of light sensitive cells whose surfaces point toward he light as it enters the eye. These main eyes have a small field of vision with high resolution. They are especially well developed in jumping spiders.
A spider’s secondary eyes also have a lens but the light sensitive cells of these eyes point away from the light as do the similar cells in a human eye. The secondary eyes detect shadows and the difference between light and dark.
There are also six-eyed, four-eyed and two-eyed spiders. Some species of spiders that live in caves and other dark places have no eyes at all. A spider’s eyes are on the top and near the front of its head.
Even though a spider has so many eyes, it can only see things a few inches from its face. To make up for their nearsightedness, spiders have a very strong sense of touch and taste. Special hairs on the spider’s body contain nerves. These nerves act as “ears, nose and tongue” to sense danger, as well as to locate food.
Web-spinning spiders are nearly blind, navigating their world mostly by touch and smell. Some spiders, such as those in the family Sicariidae, have only six eyes. Cave-dwelling species, and those which live their entire lives in the soil, may have no eyes at all.
There are also some spiders that fall between these extremes, but always with an even number of eyes. Those spiders which hunt their prey “on foot” can have very keen eyesight. Among those sharp-eyed hunters are the jumping spiders and the wolf spiders, both of which have at least one pair of very large, forward-facing eyes.