Acarina, an order comprised of mites and ticks, are of the class Arachnida. Mites live in varied habitats, and while some are highly destructive of plants, others are parasitic on and in animals, including man. Different species of ticks may be important vectors of disease of man, animals and plants.
The parasitic mites occur on a wide range of animals and in diverse habitats: they may be external or internal; and may infest the lungs, nasal passages, stomach, or body tissues. Some important parasitic mites include the chicken mite and the rat mite - both will attack man - the lung mites of monkeys, and the nasal mites of dogs. Itch mites burrow into the skin of animals including man, dogs, pigs and sheep, and cause serious injury. The chigger tick is parasitic on man and animals only during its nymphal stages. Its bites produce a severe dermatitis and may also transmit scrub typhus. Mites of the family demodicidae live in the pores of animals, including man, and may result in serious injury and death. Plant feeding mites destroy billions of dollars worth of crops each year. They cause damage by feeding on leaves and by transmitting virus diseases, such as those which distort leaves and fruits. Spider mites are perhaps the most notorious of the acarina plant pests, especially to fruit growers, as they can completely defoliate plants. Other mites infest stored agricultural products, such as grain and copra. The grain mites also cause dermatitis on those who handle stored products which the mites have damaged.