Well, I'm not sure there'd be much benefit to spending energy on a 3rd eye. You can already achieve stereoscopic vision with just two eyes, why waste the energy on a third? It probably doesn't increase fitness enough to be worth the energy spend.

Yet some creatures have many more than two eyes. Spiders, for example.

Those are not eyes though. Animals eyes always come in a pair and whether it’s a human, dog, cat, mouse etc they are Gods gateway to the soul. It’s self evident.

It might be too hard to parse, but an eye on each arm would give variable baseline and potentially 360° stereoscopic coverage.

Different sets for different wavelength ranges

>Most spiders have eight eyes. Some have no eyes and others have as many as 12 eyes.

https://www.nationalgeographic.com/animals/article/spider-se...