Arachnid are aggressive predators. They are cold-blooded; their body temperature depends on the temperature of their environment. Arachnids breathe air through book-lungs, gill-like structures.

Classification:

• Phylum Arthropoda
• Class Arachnida
  • Class Acarina (about 10,000 species of mites and ticks)
  • Class Amblypygi (about 50 species similar to whip scorpions, but with antenna-like first pair of legs)
  • Class Araneae (about 20,000 species of spiders)
  • Class Opiliones (about 2400 species of harvestmen or daddy long-legs)
  • Class Palpigradi (about 21 species of micro-whip scorpions)
  • Class Pseudoscorpionida (about 110 species of small arachnids with venomous pincers)
  • Class Ricinulei (about 15 species of ricinuleids, small, short-legged arachnids from Africa)
  • Class Scorpionida (about 600 species of scorpions)
  • Class Solfugae (about 570 species of camel or sun spiders)
  • Class Uropygi (about 105 species of whip scorpions, like the vinegaroon)