The class Arachnida is divided into 12-13 different orders including the major groups:

• Acari (mites and ticks – often classified into a superorder and divided into two or more orders)
• Amblypygi (tailless whip scorpions)
• Araneae (spiders)
• Opiliones (harvestmen or daddy longlegs)
• Palpigradi (micro whip scorpions)
• Pseudoscorpiones (pseudoscorpions)
• Ricinulei (hooded tick-spiders)
• Schizomida (short-tailed whip scorpions)
• Scorpiones (scorpions)
• Solifugae (camel spiders)
• Thelyphonida (whip scorpions or vinegaroons)

In addition, some recent research also places the Xiphosura (horseshoe crabs) into the class Arachnida.

The links provide additional information about each of the major groups of arachnids.

If you have general questions about arachnids that are not answered via our website resources, you can contact Dr. Jerry Rovner at jsrovner@~@gmail.com. See Ask a question for more details.