Arachnid

Arachnids
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Class: Arachnida
Orders
Acarina Amblypygi Araneae Opiliones Palpigradi Pseudoscorpionida Ricinulei Schizomida Scorpiones Solifuga Uropygi Parasitiformes Sarcoptiformes Trombidiformes Ref: ITIS 82708 2002-09-18

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. The arachnids are easily distinguished from the insects by the fact that they have 8 legs instead of 6. However, in some species, the frontmost pair is no longer used for walking, but has instead been adapted for sensory or reproductive functions.

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)
• Solifuga - 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

Also see the following articles for links to species by common name:

• List of scorpion common names
• List of spider common names
• List of common names for non-scorpion arachnids commonly called scorpions
• List of common names for non-scorpion arachnids not commonly called scorpions

External links:

• Arachnid Photo Gallery (The American Arachnological Society)
• International Society for Arachnology