n :  any of numerous small to very minute arachnids of the order Acarina that have a body without a constriction between the cephalothorax and abdomen, mandibles generally chelate or adapted for piercing, usu. four pairs of short legs in the adult and but three in the young larvae, and often breathing organs in the form of tracheae and that include parasites of insects and vertebrates some of which are important disease vectors, parasites of plants in which they frequently cause gall formation, pests of various stored products, and completely innocuous free-living aquatic and terrestrial forms - see ITCH MITE  .
 
 
 
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