Spiders are arthropods, but they lack the antennae of insects and crustaceans and possess a set of feeding structures called “chelicerae.” They are 8-legged arachnids, in the same family as ticks, mites, and scorpions. The largest spider by mass is the Goliath Birdeater tarantula, which can have an 11-inch leg span. Officially, the largest spider leg span belongs to the Giant Huntsman, at 12 inches. There are at least 40,000 species of spiders, and almost all of them are harmless to humans.