There are about 98,000 species of arachnids identified, and there may be many times more than that which remain unidentified. All arachnids have eight legs. They differ from insects by having no antennae or wings.

The true spiders (Order Araneae) account for about one-half of these. With so many species, there are many types, but some familiar ones include crab spiders, jumping spiders, orb-weavers and tarantulas.

Altogether, there are about a dozen Orders of arachnids. Besides the true spiders, that covers mites, ticks, solifuges, harvestmen, false scorpions, scorpions, whip scorprions and tailless whip scorpions. The harvestmen (Order Opiliones) includes the 6,600 spiders more commonly known as daddy-long-legs. There are about 1,800 scorpions (Order Scorpiones) and 150 tailless whip scorpions (Order Amblypygi). The former have stingers; the latter do not.