Arachnids are a class (Arachnida) of joint-legged invertebrate animals in the subphylum Chelicerata. Arachnids are named after the mythological figure Arachne. They are chiefly terrestrial arthropods, comprising some 65,000 to 73,000 named species including spiders, scorpions, harvestmen, ticks, and mites.CharacteristicsIt is commonly understood that arachnids have four pair of legs, and that arachnids may be easily distinguished from insects by this fact (insects have six legs or three