Arachnid : Arachnida

The arachnids, Arachnida, are a class of invertebrate animals in the subphylum Chelicerata. They are chiefly terrestrial arthropods, some 65,000 to 73,000 species including the spiders, scorpions, harvestmen[?], ticks, and mites.

Arachnids are mostly carnivorous, feeding on the body juices of insects and other small animals. Many are venomous - they secrete poison from specialized glands to kill prey or enemies. Others are parasites, some of which are carriers of disease. Arachnids usually lay eggs, which hatch into immature adults.

Orders:

• Amblypygi - "blunt rump" tailless whip scorpions
• Araneae - spiders (40,000 species)
• Opiliones - Phalangids; harvestmen, daddy longlegs (4,500 species)
• Palpigradi - microwhip scorpions
• Pseudoscorpionida - pseudoscorpions
• Ricinulei - Ricinuleids; hooded tickspiders
• Schizomida - "split middle" whip scorpions with divided exoskeletons
• Scorpiones - scorpions (2,000 species)
• Solpugida[?] - Solifugae, solifugids; wind scorpions, sun spiders (900 species)
• Uropygi - whip scorpions, with legs modified as sensory organs (60 species)

• Acari - Acarina; mites (30,000 species)
  • Acariformes[?]
    • Sarcoptiformes[?]
    • Trombidiformes[?]
  • Opilioacariformes[?]
  • Parasitiformes[?] - Holothyrans, ticks and mesostigmatic mites