Mites are small crawling animals related to ticks and spiders. Most mites are free-living and harmless. Other mites are parasitic, and those that infest livestock animals cause many diseases that are widespread, reduce production and profit for farmers, and are expensive to control. Mites are invertebrates, arthropods with a chitinous exoskeleton and jointed limbs. Within the Arthropoda, they belong in the subclass Acari (or Acarina) and species belonging to the Acari are informally known as acarines. Although both acarines and insects (class Insecta) are studied in the fields of veterinary and medical parasitology, acarines are separated from insects by structure, feeding, lifecycles, and disease relations. Both livestock and companion animals are susceptible to mite infestation and although this article will focus on livestock, the two are similar. Humans also may become infested by contagion from these domestic animals (a zoonosis). Infestation by mites usually causes skin diseases known as mange, scab, demodecosis, or in general as acariasis. The causation, economic impact, and control of these diseases in livestock are described in this article. Mites that cause disease in honey bees are described in Varroa destructor. Classification, lifecycles, anatomy, and feeding Classification Over 48,000 species of mites are described, and an estimated half-million more are yet to be discovered. Acarines parasitic on livestock animals are classified to family level in the list below. The taxonomy of the Acari is complex, several versions exist, and their phylogeny is considered to be paraphyletic (originating from several ancestral lines). The Acari are a subclass of the class Arachnida. Within the Acari are two superorders: the Acariformes and the Parasitiformes. The list below (Outline classification) is simplified for this veterinary article by omitting the superorders, orders, and suborders; this emphasizes the pragmatic taxonomic level of families, together with vernacular names. Within this list, the Parasitiformes include the blood-sucking mites of birds, the hard ticks, and the soft ticks, whilst the Acariformes include the psoroptic and sarcoptic mites, the trombiculids, and the demodectic mites. The identification of many types of mites is work for a specialist. However, the mites parasitic on vertebrate animals can readily be identified to at least the level of genus by nonspecialists if the clinical context of host species and site of infestation on skin or other organs is used. Also, the two main families of ticks are added to the list of acarine families because these common parasites are closely related