NO. 1382. 



THE ACARINA OR MITES— BANKS. 



43 



and the livpostome. These are sometimes called the pro))os('is, haas- 

 tellum, or rostrum. The hypostome is a central piece, bearing many 

 recurved teeth or denticles. The nmiiber of rows of these denticles is 

 used as a specific character in classification. At the tips of the man- 

 dibles are two or three processes known as the apophyses. They also 

 have been used in classification, l)ut are variable. The palpi are 

 always very short and stout and compo.sed of four articles, not, how- 

 ever, very distinctly. Some species have eyes situate one at each 

 lateral angle of the scutum. The posterior margin of the body, 

 especially of the male, is usually somewhat lol)ate. the.se lo])es being- 

 known as the posterior marginal festoons. The stigmata or spiracles 

 are above and usually l)ehind the coxa' W . Each is surrounded by a 

 reticulated or pitted plate of var3dng outline, and called the peritreme 

 or stigmal plate. It is ofte'n of 

 large size. Ui)on the venter there 

 are several furrows characteristic 

 in position and of value in classi- 

 fication. The anal opening is a 

 small, circ-ular hole some distance 

 behind the coxtv IV; the genital 

 2:)()re is situate on the front of the 

 sternal area, slightly behind the 

 mouth-orifice. The legs arise 

 close together. Ijut in the dis- 

 tended females the coxa* l)ecome 

 quite widely separated. There 

 are six joints in the leg — coxa, 

 trochanter, fenmr, tibia, protar- 

 sus or metatarsus, and tarsus; the 

 latter is sometimes divided, while 

 the femur often presents a basal 

 distinct portion, which may be the 

 trochantin. Upon the tarsus of the first pair of legs is a depressed 

 circular area, supposed to be an organ of hearing; it is known as Mai- 

 lers organ, in honor of its discoverer. The tarsus terminates in a short 

 stalk that bears the two claws and the pulvillus or caruncle. The 

 body of a tick is usually dull colored, but some forms are mottled 

 with brown and yellowish or reddish. 



Ticks are parasitic on mammals, birds, and reptiles. But at times 

 the}' may leave their host, and are not confined to one host, althougii 

 some species show a prefei-ence. Most of them do but little damage 

 to their hosts while sucking blood, but several closely allied species 

 belonging to the genus ^o<'>;>/'/7?a,v transmit an organism, i\\Q Pyroscmta 

 ht(ji'iiinilnnriu that causes a disease in cattle known as Texas fever. 

 Southern cattle fever, red-water, heart-water, etc. As a result of her 

 bloodthirstv nature the feujale tick liecomes enormouslv distended. 



Fig. 73. — Booi'iiilus annulatus, fe.male. 



