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• Physical characteristics
• Scorpions
• Spiders
• Mites and ticks
• Harvestmen (daddy longlegs)

Arachnids (pronounced uh-RACK-nidz; class Arachnida) form the second-largest group of land arthropods (phylum Arthropoda) after the class Insecta. There are over 70,000 species of arachnids that include such familiar creatures as scorpions, spiders, harvestmen or daddy longlegs, and ticks and mites, as well as the less common whip scorpions, pseudoscorpions, and sun spiders. The marine horseshoe crabs and sea spiders are near relatives.

Physical characteristics

Arachnids have paired, jointed appendages (parts that are attached to the main body), a hardened exoskeleton (exo means "outer"),...