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There are over 100,000 species of arachnids in the world. These include spiders, scorpions, harvestmen, ticks and mites. The word arachnid is from the Greek word arachne meaning spider. Arachnids are not insects, but they are related. Arachnids and insects are both arthropods. It is easy to tell the difference between an arachnid and an insect. Arachnids have eight legs and insects have only six legs. Another difference is that arachnids don't have antennae or wings like insects. Check out these videos to learn more about arachnids of North America and other parts of the world.