You might often find spiders making a nest or web in high places at homes or trees to catch their prey. However, do you know that some spiders walk on the ground while hunting? Have you ever looked closely to their heads? Also, can you guess how many eyes do spiders have?
You would not bother thinking how many eyes spiders have if you are arachnophobia because their heads are somewhat creepy to look. You would not even dare to zoom in.
How Many Species Are There?
Spiders have more than 43,000 different species worldwide. They are grouped to the class arachnid, including spiders, scorpions, ticks, and mites. To distinguish arachnids and insects, you can look at their legs. Arachnids have eight legs, while insects only have six.
There are mainly two groups of spiders, which are weaving spiders and hunting spiders. Weaving spiders would make a web and wait for their prey. Nevertheless, they possess rather terrible eyesight, so they rely on vibration and touch.
On the other hand, hunting spiders, such as wolf spiders, jumping spiders, and bolas spiders, have exceptional eyesight that tremendously helps them find insects and protect themselves from predators.
Again, how many eyes do spiders have? Well, around 99% of them have eight eyes, some only have six, some others have four, and there are even spiders with vestigial eyes or no eyes at all.
Spiders have two main types of eyes, and they are the primary eyes called ocelli and secondary eyes. Most spiders have poor eyesight, but the primary eyes of jumping spiders are far better than insects with the best vision, dragonflies.
The primary eyes have muscles to move the retina to bring a focus and track images while the secondary eyes are for tracking movements and gauging distances, and they are usually smaller than the primary eyes. They also lack muscles and are stationary.
Spider Eyes of Row
The ocelli are facing to the front and are also referred to as Antero-media eyes or AME for short. You can identify a spider’s eyes due to their placement. There are two rows of spider eyes arrangement.
On the side of the head are called the anterolateral eyes (ALE), which is on the top row. For the second row located on the site of the head are called the postero-lateral eyes (PLE) and the posteromedial eyes (PME) which are located in the middle of the head.
From the number and arrangement of spider eyes, arachnologists can classify what species they belong to because spiders have many eyes with different numbers and locations on their heads.
These spiders are identified to have eight eyes including wolf spiders (Lycosidae), jumping spiders (Salticidae), flower spiders (Thomisidae), orb weavers (Araneidae), and cobweb weavers (Theridiidae).
Moreover, this list belongs to the group of spiders, which have six eyes such as recluse spiders (Sicariidae), the spitting spiders (Scytodidae), and some of the cellar spiders (Pholcidae).
Those spiders that come from the Symphytognathidae family and some spiders in the Necticidae family have four eyes.
As I mentioned above, some spiders only have two eyes, and they belong to the family Caponiidae.
There are some spiders with vestigial eyes or no eyes at all. These spider species only live in caves or underground that may cause to lose their sight. They typically belong to the eight-eyed spider or six-eyed spider family.
Those are some facts about spiders’ eyes that may solve the question of “how many eyes do spiders have?”