Acarina 259 



ACARINA* 



a. Abdomen annulate, elongate; very minute forms, often with but four legs 



(fig. 62) Demodicoidea 



b. With but four legs of five segments each. Living on plants, often forming 



galls ERI0PHY1D.E 



bb. With eight legs, of three segments each. Living in the skin of mammals 



DEMODICID^ffi 



To this family belongs the genus Demodez found in the sebaceous glands 

 and hair foUicles of various mammals, including man. D. phylloides 

 Csokor has been found in Canada on swine, causing white tubercles 

 on the skin. D. hovis Stiles has been reported from the United States 

 on cattle, upon the skin of which they form swellings. D. folliculorum 

 Simon is the species found on man. See page 78. 

 aa. Abdomen not annulate nor prolonged behind; eight legs in the adult stage, 

 b. With a distinct spiracle upon a stigmal plate on each side of the body (usu- 

 ally ventral) above the third or fourth coxse or a little behind (fig. 50) ; 

 palpi free; skin often coriaceous or leathery; tarsi often with a sucker. 

 c. Hypostome large (fig. 50), furnished below with many recurved teeth; 

 venter with furrows, skin leathery; large forms, usually parasitic 



IXODOIDEA 



d. Without scutum but covered by a more or less uniform leathery integu- 

 ment; festoons absent; cox^ unarmed, tarsi without ventral spurs; 

 pulvilli absent or vestigial in the adults; palpi cylindrical; sexual 



dimorphism slight ARGASID.ffl 



e. Body flattened, oval or rounded, with a distinct flattened margin 

 difEering in structure from the general integument; this margin 

 gives the body a sharp edge which is not entirely obliterated even 

 when the tick is full fed. Capitulum (in adults and nymphs) 

 entirely invisible dorsally, distant in the adult by about its own 



length from the anterior border. Eyes absent Argus Latr. 



f. Body oblong; margin with quadrangular cells; anterior tibise and 

 metatarsi each about three times as long as broad. On poultry, 



southwest United States A. persicus miniatus 



A. brevipes Banks, a species with proportionately shorter legs has 

 been recorded from Arizona, 

 ff. With another combination of characters. About six other species 

 of Argas from various parts of the world, parasitic on birds and 

 mammals. 

 ee. Body flattened when unfed, but usually becoming very convex on 

 distention; anterior end more or less pointed and hoodlike; 

 margin thick and not clearly defined, similar in structure to the 

 rest of the integument and generally disappearing on distention; 

 capitulum subterminal, its anterior portions often visible dorsally 

 in the adult; eyes present in some species, 

 f. Integument pitted, without rounded tubercles; body provided 

 with many short stiff bristles; eyes absent. On horses, cattle 



and man (fig. 48) Otiobius Banks. 



O. megnini, a widely distributed species, is the type of this genus . 

 ♦Adapted from Banks, Nuttall, Warburton, Stiles, el. al. 



