Arachnids have 8 legs and do not have wings. They have 2 body parts: the front part (cephalothorax or "head/thorax") has the mouth, eyes, and legs, and the back part (abdomen) is the rest of the body.

Spiders Araneae The two body parts are distinct and narrow where they join; body does not have segments	Scorpions Scorpiones The two body parts are distinct, but thick where they join; pincers in front, stinger behind.	Harvestmen Opiliones The two body parts are joined thickly, giving the appearance of a single segmented body.
Pseudoscorpions Pseudoscorpiones The two body parts are distinct, but thick where they join; pincers in front, no stinger.	Mites and ticks Acari The two body parts are joined thickly, giving the appearance of a single body; body does not have segments.	Wind Scorpions Solifugae Large mouthparts (chelicerae) in front; long pedipalps (similar to insects' antennae) resemble an additional pair of legs.

Arachnid Orders: Acari; Araneae; Amblypygi; Opiliones; Palpigradi; Pseudoscorpiones; Ricinculei; Scorpiones; Solifugae; Thelyphonida