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1. A minute arthropod of the order Acarina, a vast assemblage of parasitic and (primarily) free-living organisms. Most are still undescribed, and only a relatively small number are of medical or veterinary importance as vectors or intermediate hosts of pathogenic agents, by directly causing dermatitis or tissue damage, or by causing blood or tissue fluid loss. The six-legged larvae of trombiculid mites, the chigger mites (Trombicula), are parasitic of humans and many mammals and birds; they are important as vectors of scrub typhus (tsutsugamushi disease) and other rickettsial agents. Some other important mites are Acarus hordei (barley mite), Demodex folliculorum (follicular or mange mite), Dermanyssus gallinae (red hen mite), Ornithonyssus bacoti (tropical rat mite), Ornithonyssus bursa (tropical fowl mite), Ornithonyssus sylviarum (northern fowl mite), Pyemotes tritici (straw or grain itch mite), and Sarcoptes scabiei (itch mite).