Mites (Order Acari)

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.

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 absense of abdominal segmentation (right).

From our perspective the most important mites are ticks (because their carry diseases), spider mites and eriophyid mites (because they are agricultural pests), phytoseiid mites (because they prey on agricultural pests), and, dust mites and grain mites (because they cause allergy and asthma).

Mites that bite or cause allergy

Ticks (Ixodidae & Argasidae) are exclusively parasitic mites that feed on the blood of amphibians, reptiles, birds and mammals (vertebrates). 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 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.