A class of chelicerate arthropods that includes spiders, scorpions, mites, and ticks. They have become adapted for a terrestrial life and possess both lungs and tracheae, and many have silk or poison glands.‘The Arachnida include the terrestrial chelicerates that everyone is familiar with, and that nearly everyone would rather not be too familiar with: spiders, ticks and mites, and scorpions (Scorpiones).’
- ‘Ticks belong to the class Arachnida, which counts mites, spiders and scorpions among its members.’
- ‘However, they were not true spiders, nor necessarily ancestral to them, but represented independent offshoots of the Arachnida.’
- ‘The study of the Southern African baboon spiders form part of the South African National Survey of Arachnida.’
- ‘The Arachnida are notorious for the venomous organisms that form part of this class.’
Modern Latin (plural), from Greek arakhnē ‘spider’.