What a ridiculous question, how many eyes does a spider have. Spiders have eight eyes, right? Or do they? Well, to an extent, that is correct. But wait! Not ALL spiders have eight eyes, did you know that? Read on to find out more.
In general, yes, spiders have eight eyes. In fact, 99 percent of spiders have eight eyes. There are a few however, that have 2, 4 or even 6 eyes. There are even some spiders that have no eyes at all.
So yes, the vast majority of spiders do in fact have eight eyes. But why so many? They’ve already got all the legs, why do they need all the eyes too? Let’s have a closer look…
Why Eight Eyes?
Spider’s eyes are completely fixed. That is, they’re unable to give you the side-eye or glance up or down. So, they need eight eyes to be able to see all around.
The front eyes focus on hunting prey, whilst the eyes on the side of their head are used primarily for detecting motion.
This is imperative as without being able to detect motion, they could end up as a larger predator’s dinner or even worse, squished.
As you may or may not be aware, despite all these eyes, spiders have pretty rotten eyesight.
They can only see the difference between light and dark most of the time and can only actually visibly SEE if things are extremely close-up to them.
There are a few exceptions to this that includes the jumping spider and flower spider.
These spiders hunt during the day and use mainly their eyesight to hunt prey (they don’t build webs like most spiders).
The wolf spider hunts at dawn or dusk, in a similar fashion to tarantulas, again, not by utilising a web but by actively stalking and catching its meals.
Two Eyed-Spiders
Most species of the Caponiidae spider have only two eyes, however some species of Caponiidae can have four, six or even the standard eight eyes.
In some species the number of eyes will increase when the spiderling changes its skin as it grows towards adulthood.
In some species of the Caponiidae, a pair of eyes meet in the midline, giving the spider in effect, an odd number of eyes. The following genera have eyes as follows:
Eight eyes: Calponia, Caponia (but latter may also have two, three, four or ‘five’ eyes)
Six eyes: Iraponia
Four eyes: Nopsides, Notnops
Two eyes: Cubanops, Diplogena, Laoponia, Medionops, Nops, Nopsma, Nyetnops, Orthonops, Taintnops, Tarsonnops, Tisentnops.
In this they surpass even the family Cybaeidae in which some species have two eyes, some six, and some eight eyes.
The net-casting spider – family Deinopidae – has two huge rear eyes that are very efficient when it comes to seeing in low light.
Every night, a new light-sensitive membrane is produced in the eye, and every morning, the previous night’s membrane is destroyed.
The net-casting spider uses its extraordinary eyesight to track and “net” its prey. The appearance of the two large rear eyes gives these spiders another nickname – the ogre-faced spiders.
Four Eyed Spiders
The cutest spider of them all has four eyes. Yes, it’s the jumping spider. I’m just going to gratuitously put a massive picture of one here….
Isn’t it adorable?!
Actually, I’ve just told you a little fib. These guys have eight eyes but it just appears that they have four.
Here’s another image that shows the eyes on the side of their head proving they do in fact have eight.
*ahem* Moving on…..
Four or Less Eyes
There are a few species of spiders – like Sinopoda scurion, a cave-dwelling huntsman – that have no eyes at all. This part of the Sinopoda genus was spotted in Laos by Senckenberg Research Institute zoologist Peter Jäger, who has been studying the country’s arachnids since 2003.
It has been suggested that cave-dwelling creatures that evolve without eyes do so to allow for conservation of energy, using their antennae and chemical touch receptors to hunt instead.
The Kauai cave wolf spider (Adelocosa anops) lost its eyes after living in a series of Hawaiian caves. The endangered species hunts by sensing chemical compounds in the earth.
Finally, the Braken Bat Cave mesh-weaver was on the endangered list but has been synonymized with the Madla Cave meshweaver. However, it is still an eyeless spider.
So there you have it. Whilst the majority (99 percent) of spiders have eight eyes, there are a few variations, albeit slim.
Now you’ve read how many eyes a spider has, maybe you’d be interested in reading about their heart, here? Until next time, stay tuned for more interesting facts on Spider Advisor!