Mites include species such as the northern fowl mite and tropical rat mite. These are extremely small mites (1/64 to 1/32 inch), but they are visible. Their color varies from white to dark gray as they age and feed. They are usually associated with wild birds and their nests (northern fowl mite) and rodents, such as hamsters (tropical rat mite).

These mites pass through life stages including the egg, larva (3 pairs of legs), and 2 nymph stages before becoming adults. Fowl mites lay 2 to 3 eggs per day on the host, while rat mites lay batches of eggs near rodent bedding. Adult fowl mites can survive off the host for 2 to 3 weeks, and rat mites can survive up to 9 weeks without a meal. When the host vacates a nest or burrow, these mites will seek new hosts and may bite people. However, these mites cannot reproduce by feeding on people and normally only survive for several weeks off their primary host.

Although fowl and rat mite bites are not extremely irritating, they can be a periodic nuisance for those affected. Birds that nest in or on structures will leave behind nesting material full of hungry mites seeking hosts. Tropical rat mites may migrate if their rodent host dies. This species is also common on pet store rodents, such as hamsters, and can become a problem if the cage is not cleaned regularly.