For many people, the sight of a spider is not a welcoming experience. The long legs, fast pace in dim light and their ability to make their often unwelcome presence known just as you are ready to take a nap or sleep is unmatched. But if you take a little time to get to know them, how they look, how they behave and what they do, they can give a sense of curiosity, and wonder.
When asking the average person how many eyes do spiders have, the most common answer you get back is two. Because despite all the fear, the apathy or even hate, most people don’t pay that much attention to the details of how these creatures actually look. In most cases, spiders have much more than two eyes, and this is the theme we are exploring in this post.
How Many Eyes Do Spiders Have On Average?
The vast majority of spiders have 8 eyes, and given that there are over 34,000 species of spider known to exist, that’s a lot of 8 eyed arachnids out there! But spiders don’t see like we do. Their eyes generally are not nearly as good as human eyes. While most have 8 eyes, they don’t all work in the same way. They will usually work in pairs (left and right) but each pair may perform a different function or see if a different way.
For spiders that have eight eyes, they are usually categorised as two rows of four, then into pairs. The two rows are known as the Anterior and the Posterior rows, and the pairs are known as Median or Lateral based on their location. So they will have a set of Anterior Median Eyes (AME), and a pair of Anterior Lateral Eyes (ALE) and the same for the Posterior sets (PME), (PML).
Examples Of Spiders With 8 Eyes
Examples Of Spiders With 6 Eyes
Some examples of spiders with 6 eyes include:
What’s The Least Amount Of Eyes A Spider Has?
Some spiders have no eyes at all! There are only a few species with no eyes, but those that are blind utilise their other senses for hunting, and for alerting to danger. Those that have no eyes, are usually found in cave or underground environments where the function of an eye is greatly redundant.
Examples Of Spiders With No Eyes
- Sinopoda Scurion
- Kauaʻi Cave Wolf Spider
Some spiders have two eyes, but the species that fall into this category all belong to one family – Caponiidae. There are 124 know species in this family.
What’s The Most Eyes A Spider Has?
There are some sources that claim spiders have up to 10 – 12 eyes, but this would appear to be false. Of all the spider species documented so far, 8 eyes appears to be the most that a spider has. The fewer the eyes, the fewer the species that fall into that category.
What Type Of Eyes Does A Spider Have?
Not all spiders eyes are the same. For those with multiple pairs of eyes, each pair may perform a different function. The Australian Jumping Spider for example, has two very large front eyes that perceive color and images with depth of field, with six smaller side eyes to detect movement. These different types of eyes are known as Principal and Secondary eyes.
All spiders (with exception to those with no eyes) have a set of principal eyes. These are the main set of eyes, usually larger than any secondary eyes they may have. The principal eyes are those responsible for producing color for those that are able to perceive this. They also produce the depth of field that spiders have. They do however have short lenses and a short focal length.
There are three types of secondary eyes that a spider may have. These are:
- Primitive Type
- Canoe Type
- Grate Type
It is only the Grate Type of secondary eye that can produce sharp, in-focus vision. These types of eyes are usually found on a select few hunting spiders.
How Good Is A Spider’s Eyesight?
While some spiders such as the wolf spider, rely on good eyesight for catching food, most spiders don’t have good eyesight at all. In fact many can only differentiate between light and dark, and do not see in color.
On the other hand, according to the national geographic, there are some spiders that have very good vision, to the extent of being able to react to shapes on a television monitor. That kind of vision allows for spiders to determine movement of 2D images on the surface of a 3D shape. It’s rare in arachnids to have this quality of visibility. Jumping spiders are perhaps the best example of this.
Why Do Spiders Have So Many Eyes?
Spiders can’t move their necks like we can. They can’t more their head from side to side without moving their entire body So to be able to see a wider range of vision, they need more eyes. Jumping spiders for example can cover 360 degrees across their range of eyes, something we can only do by rotating our heads from side to side.
How Spiders Compensate For Poor Vision
For species that have bad eyesight, spiders can utilise other senses to compensate for poor vision. The are able to acutely sense vibrations though hairs (trichobothria) and tiny slits that cover their bodies. This allows them, with their limited vision to produce a greater sense of any movement, be it prey or predator, or even the wind.
If you are a fan of the Spiderman comics or films, you will recognise this is a real world ‘spidey sense’ where these sensitive hairs act as a sixth sense. They can also taste and smell through their legs!
While most spiders have 8 eyes, they don’t all have good vision. There are a variety of different types of eye that spiders can have, that determine how good they are at perceiving light, colour, shape and distance. Some spiders are know to have 6, 4, 2 or even no eyes at all. But the fewer the number of eyes, the fewer the species.