Arachnida (Arachnids)

The class Arachnida, more commonly known as Arachnids, is a classification that include scorpions, pseudoscorpions, harvestmen, ticks, mites and spiders.

Distinguishing features of the class Arachnidna compared to the class Insecta include:

• adult arachnids have eight legs attached to the cephalothorax. In some species the front most pair of legs has converted to a sensory function, while in others, different appendages can grow large enough to take on the appearance of extra pairs of legs.
• arachnids retain their adult shape and molt (shed their exoskeleton) as they grow larger, whilst insects undergo metamorphosis from a larva to an adult.
• arachnids have no antennae and no wings. Insects have wings and antennae.
• arachnids have two body parts — a cephalothorax and an abdomen. Insects have three body segments — a head, a thorax and an abdomen.
• arachnids have eight legs arranged in four pairs. Insects have six legs arranged in three pairs.

When distinguishing by common names, it is not always obvious which class they belong to ie Water Scorpion (Laccotrephes tristis) are in the class Insecta and not in the class Arachnida.

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• Scientific classification
• Kingdom: Animalia
• Phylum: Arthropoda
• Subphylum: Chelicerata
• Class: Arachnida
• Order:
  • Amblypygi
  • Araneae
  • Opiliones
  • Palpigradi
  • Pseudoscorpiones
  • Schizomida
  • Scorpiones

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