Acarina
Amblypygi
Araneae
Opiliones
Palpigradi
Pseudoscorpionida
Ricinulei
Schizomida
Scorpiones
Solifugae
Uropygi
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.