5 Fun Facts About the Spider 1. There are approximately 40,000 known species of spiders,…

5 Fun Facts About the Spider 1. There are approximately 40,000 known species of spiders, which may be only one third of the actual number of spider species living on the planet. 2. Though spiders have simple eyes, they usually are not well developed. Instead, spiders use vibrations, which they can sense on the surface of their web. 3. Spiders are arthropods, so their skeletal system of their body is the outermost layer. The hard exoskeleton helps the spider maintain moisture and not dry out. 4. Although insects and spiders belong to the same taxonomic phylum, Arthropoda, they look very different from one another. These physical differences are what separate them in to two classes: Insecta and Arachnida. 5. The word spider is from an Old English verb spinnan, meaning "to spin." Web weavers use the tiny claws at the base of each leg, in addition to their notched hairs, to walk on their webs without sticking to them.