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 . Eriophyid^e 
bb. With eight legs, of three segments each. Living in the skin of mammals 
. Demodicid,® 
To this family belongs the genus Demodex found in the sebaceous glands 
and hair follicles of various mammals, including man. D. phylloides 
Csokor has been found in Canada on swine, causing white tubercles 
on the skin. D. bovis 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 coxae 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 furrow's, skin leathery; large forms, usually parasitic 
. IXODOIDEA 
d. Without scutum but covered by a more or less uniform leathery integu¬ 
ment; festoons absent; coxae unarmed, tarsi without ventral spurs; 
pulvilli absent or vestigial in the adults; palpi cylindrical; sexual 
dimorphism slight. Argasid^e 
e. Body flattened, oval or rounded, with a distinct flattened margin 
differing in structure from the general integument; this margin 
gives the body a sharp edge which is not entirely obliterated even 
w'hen 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 tibiae 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 
wfith 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, et . al . 
