How Well Can Jumping Spiders See? Big Eyes and Color Vision

Eight eyes with different jobs

All jumping spiders have eight eyes, arranged so that the spider can see almost 360 degrees around itself. Each pair has its own role:

The secondary eyes, the six smaller ones, detect movement and trigger the spider to turn. Once it faces the object, the principal eyes take over and identify it. Experiments have shown that a jumping spider with only its anterior lateral eyes uncovered can still detect, stalk and catch flies, so even the “secondary” eyes are surprisingly capable.

Telescope eyes with movable retinas

The principal eyes are the stars of the system. Each one is built like a small telescope: a lens at the front, a long tube, and a second lens near the back that magnifies the image onto the retina. The retina is not a broad sheet as in our eyes but a narrow, boomerang-shaped strip.

The lens is fixed in the body wall, so the spider cannot move its eyes as we do. Instead, muscles move the retinas behind the lenses, sliding and rotating them to scan an object piece by piece. In young spiders with translucent bodies, and in some species with pale heads, you can actually see the dark retinas shifting as the spider looks around.

The sharpest region of the retina is tiny, only a few receptor rows wide, and the field of view of each principal eye is just a few degrees. The spider makes up for this by scanning, much as we move our eyes to look at different parts of a scene.

How sharp is jumping spider vision?

For an animal a few millimeters long, very sharp. Jumping spiders resolve details far finer than most insects, whose compound eyes are limited by the size of each tiny facet. The best-studied species, such as those in the genus Portia, have eyesight that is still several times coarser than human vision, but outstanding for an animal with a brain smaller than a pinhead.

This sharp vision lets them recognize prey, rivals and mates by their shape and markings. Jumping spiders can distinguish a fly from an ant, can follow moving targets, and in lab tests have learned to tell apart shapes and colors.

How do jumping spiders judge distance?

To jump accurately, a spider must know exactly how far away its target is. Its two principal eyes are too close together for the kind of depth perception humans use. A 2012 study on the jumping spider Hasarius adansoni proposed an elegant answer.

The principal retina has four layers. Because the lens focuses different colors at slightly different depths, green light is sharply focused on the deepest layer, while the layer just above it, which also responds to green, always receives a blurred image. The amount of blur changes with distance, so comparing the sharp and blurred images tells the spider how far away the object is. When researchers lit the spiders with red light, which changes the blur, the spiders misjudged distance and fell short in their jumps.

The anterior lateral eyes, which are wider apart, may also help judge distance. Read how this feeds into the leap itself in how jumping spiders jump.

Can jumping spiders see color?

Yes. Their principal retinas contain receptors sensitive to ultraviolet and green light, and many jumping spiders appear to have good color vision. Some species have red filters in front of some of the green-sensitive receptors, giving them sensitivity to red as well. Ultraviolet patterns play a role in courtship in some species, with males showing markings that are visible only in UV light.

This helps explain why many male jumping spiders are so colorful and perform elaborate visual dances to attract females.

Vision in the zebra jumping spider

The zebra jumping spider of walls in Europe and North America is a good example. It turns toward a moving object once it appears large enough to its side eyes, studies it with its principal eyes, and stalks prey, slowing down as it gets close. Its black-and-white pattern also plays a part in courtship, when males display to females by sight.

How do jumping spider eyes compare with other spiders?

Most spiders have poor vision. Web-building spiders rely on vibrations in the silk, and many hunting spiders see little more than light, shadow and movement. Wolf spiders have better night vision, helped by a reflective layer that makes their eyes shine in a flashlight beam, as explained in why wolf spider eyes glow. Jumping spiders are the daytime specialists: their eyes work best in bright light, and they rest at night.