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Mites (Order Acari)
- Most are tiny but extremely diverse and important -
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Summary: Mites are an extremely diverse and important group of arthropods. Some feed on plants (spider mites) while others, like ticks, chiggers, mange and scabies mites are ectoparasites of vertebrate animals. Still others are predators. The study of mites is called Acarology.
Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)
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What are mites?
 Mites are an extremely diverse and important group of arthropods that are related to spiders, scorpions, and a host of lesser-known arachnids. While other arachnids are exclusively predatory, mites exhibit a great diversity of lifestyles. Some mites feed on plants while others feed on animals (ectoparasites), and some are predators like their arachnid relatives.
All mites share the following characteristics: Like other arthropods mites have jointed legs and an external skeleton, or exoskeleton. Mites also lack antennae and mandibles, or jaws, which distinguishes them from insects. Finally, mites and ticks are distinguished from all other arachnids by the absence of any abdominal segmentation (right).
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| Tyrophagus - a grain mite, is closely related to dust mites |
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| From our perspective the most important mites are ticks because they bite and carry diseases, spider mites because they damage plants, dust mites because they cause allergy and asthma, and several mites that infest people and animals including mange and scabies mites, and chigger mites.
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Some mites found on plants
Spider mites (Tetranychidae) feed exclusively on plants. They are perhaps the most important agricultural pests worldwide. Some researchers estimate that spider mites reduce total agricultural production by up to 5%.
Eriophyid mites (Eriophyidae) are tiny, nearly microscopic mites called leaf vagrants, bud mites and gall mites. Most cause their plant hosts to produce a gall of abnormal tissue on which the mites feed. Some cause extreme leaf deformity. They are distinguished from other mites by having only two pair of legs as adults.
Phytoseiid mites (Phytoseiidae) are predators of spider mites and other plant feeding mites.
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Mites that bite or cause allergy
Ticks (Ixodidae & Argasidae) are exclusively ectoparasitic mites that feed on the blood of amphibians, reptiles, birds and mammals. They are extremely important as vectors of certain human diseases like Lyme Disease and many others.
There are also some small mites that bite and cause skin lesions. Biting mites occur in very specific habitats such as near bird and rodent nests. See the Mites That Bite Guide (pdf) which describes some of these species.
Dust mites (Acaridae: Dermatophagoides) are very closely related to grain mites but feed on shed skin cells rather than fungi. Dust mites are important because they produce allergens in their droppings to which some people are highly allergic. Grain mites (Acaridae: Tyrophagus) are somewhat misnamed since they really feed on the fungi that grows on damp grain and in other damp situations. They can be very important household and warehouse pests. When present in high numbers grain mites can cause allergic reactions in some people as well.
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Some tiny mites specialize in feeding on the skin of warm-blooded animals, including us, rather than blood as ticks do. Chigger mites are the larval (six-legged) stage of a predator mite. Chiggers feed on skin cells and cause a very itchy rash but do not burrow into the skin. Mange and scabies mites, on the other hand, actually burrow into the skin causing a very irritating condition. Mange is the condition when it occurs in animals and scabies is the condition in humans.
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