Arachnida

Examples of arachnids:

• spiders
• scorpions
• ticks
• mites

General characteristics:

• cephalothorax with six pairs of appendages:
  • chelicerae (pincers or fangs), a pair of appendages called pedipalps that usually function in sensing or feeding.
  • four pairs of walking legs

The Arachnida include several other orders, too. They are:

• Opiliones - Harvestmen
• Solifugae or Solpugida - Camel spiders (also called sun spiders or windscorpions)
• Schizomida - Schizomids
• Ricinulei - Ricinuleids
• Amblypygae - tailless whipscorpions (AKA whip-spiders)
• Uropygae - Whipscorpions or uropygids
• Palpigradi - Palpigrades
• Pseudoscorpiones - false scorpions

A*rach"ni*da (#), n. pl. [NL., fr. Gr. spider.] Zool.

One of the classes of Arthropoda. See Illustration in Appendix.

⇒ They have four pairs of legs, no antennae nor wings, a pair of mandibles, and one pair of maxillae or palpi. The head is usually consolidated with the thorax. The respiration is either by trancheae or by pulmonary sacs, or by both. The class includes three principal orders: Araneina, or spiders; Arthrogastra, including scorpions, etc.; and Acarina, or mites and ticks.

© Webster 1913.