How Do Spiders See?
WouterSpiders see well enough to catch prey, but they don’t see much else. They have two large front eyes, one small side eye, and four secondary eyes. The principal eyes are able to detect color, but the rest are just good at detecting movement and motion.
The principal eyes are arranged in an “X” pattern. The X-shaped structure has six muscles that enable the eyes to move independently, allowing spiders to rotate and scan a narrow boomerang-shaped strip of their environment.
The secondary eyes are located on either side of the head and are used to detect motion. These tiny sensors pick up the slightest changes in air pressure. In addition, they can also sense vibrations.
Some species of spiders have a layer of iridescent material behind their retinas, which provides an iridescent glow. This helps them to see the colors of light, even in dark areas. The iridescent layer is called the tapetum.
Jumping spiders have two huge front eyes, which are used to judge distance, and a pair of smaller side eyes, which are used to detect motion. The largest front eyes provide a clear telephoto image, while the side eyes give a blurry wide-angle view. The jumping spider’s primary and secondary eyes are designed to take in red, green, and ultraviolet wavelengths of light.
A scientist at the University of Pittsburgh discovered that some spiders have a red filter in their principal eyes. This enables them to detect red light, which adds red hues to their world.
