The subclass Acari comprises mites and ticks. It is the most diverse group of all the Arachnida and in total there are currently 45,231 described species.

They are found throughout the world in:

  • decomposing organic matter and soil
  • plants
  • freshwater
  • deep marine habitats
  • on and in animals

Because of their feeding habits, some acarines are of medical importance. For example, ticks transmit a greater number of diseases than any other arthropod worldwide.

Mites are also of commercial and agricultural importance, being parasites of crops. They can also be extremely useful as bio-control agents, especially on other mites that are plant parasites.