Acari

Definition

A historically recognized subclass of Arachnida encompassing mites and ticks. The group comprises two major superorders—Acariformes (most mites) and Parasitiformes (ticks and some mites)—though recent phylogenetic analyses indicate Acari is paraphyletic and does not represent a true clade. Members are characterized by minute size, reduced body segmentation, and diverse life histories spanning free-living decomposers, plant feeders, predators, and obligate parasites of vertebrates and invertebrates.

Etymology

New Latin, plural of Acarus, the typical genus of mites

Example

The honey bee parasite Varroa destructor and the Lyme disease vector Ixodes scapularis are both traditionally classified within Acari.

Synonyms

• Acarina

Related Terms

• Acarology
• Acariformes
• Parasitiformes
• Arachnida
• Mite
• Tick
• ectoparasite

Usage Notes

Acari remains widely used as a convenient collective term in applied contexts (medical/veterinary entomology, agriculture) and in the name of the discipline acarology, but systematists increasingly avoid the rank or treat it as an informal grouping. Contrast with Opiliones (harvestmen), which are unequivocally monophyletic arachnids outside this assemblage.