mite, small, often microscopic arachnid that belongs to several orders in the subclass Acari (or Acarina), to which the tick also belongs; mites and ticks are related to the spiders. The unsegmented mite body is typically oval and compact, although a few, mostly parasites, are elongated and wormlike. There are four pairs of legs. The movable head is attached to the body by a hinge. There are four stages in the life cycle: egg, larva, nymph, and adult.
The thousands of different mite species are worldwide in distribution and occupy diverse habitats, including plant galls, mosses, other animals, and surface litter or upper layers of the soil. One group, the water mites, has returned to an aquatic environment, both fresh- and saltwater. Mites eat plant or animal substances, decaying organisms, and humus, and also infest stored food products such as cheese, meat, grains, and flour. The spider mite, or red spider, which is a mite and not a spider, feeds on plants and is destructive to crops. Many mites are parasitic on other arthropods, on mollusks, or on vertebrates. Mange and scabies mites lay their eggs in the skin and cause irritation in humans and fur-bearing animals. Other species are parasitic on the skin of birds and reptiles, and some live in the respiratory channels of birds and mammals. Chiggers, the larvae of harvest mites, transmit the organism that causes scrub typhus. Fowl mites feed on the blood of poultry. House dust mites, which thrive in moist environments and eat flakes of human skin and other minute organic material, produce digestive enzymes that are excreted in their feces and produce allergic reactions in many people.
Mites belong in the phylum Arthropoda, subphylum Chelicerata, class Arachnida, subclass Acari.