out in the sticks has added a photo to the pool:
People are often surprised to learn that (most) spiders have eight eyes. Although once a friend did ask me, WHY do they have eight eyes. Honestly, I have no idea. In some, like jumping spiders, where all the eyes serve a different purpose, I can understand, but many spiders, suh as this Tegenaria house spider, can barely see at all, their eyes are much less useful to them than those thick spines on their legs which do far more to help them sense what is going on around them. As all spiders have either six or eight eyes (although interestingly most other arachnids only have two), I can only assume that they must have evolved from an ancestral invertebrate with a large number of eyes, even though those eyes may not have been of a huge amount of use.
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