THE MITES AND TICKS 



3211 



Of all the Acari the best known and most troublesome are those belonging to 

 the family Ixodidce, which infest terrestrial vertebrates, and sometimes attach 

 themselves to men. They are furnished with a longish, cylindrical beak, armed 

 with recurved hooks, and formed by the two mandibles 

 above and the long slender labium below. The palpi 

 are either free, as in Argas, or closely applied to the 

 beak, forming in fact a sheath for it, and preventing 

 the escape of blood, which flows from the puncture 

 made by the beak. In the accompanying figure, 

 showing the mouth parts of the common English dog 

 or sheep tick (Ixodes rtdnus), the lower surface of 

 the capitulum, or head-like process, which bears the 

 beak is shown at c; d, <?, _/, g, represent the four seg- 

 ments of the palpi; h is the labial process armed with 

 the hooks forming the lower side of the beak; and z 

 indicates the tips of the two mandibles, forming its 

 upper side, and projecting beyond the apex of the 

 labium. By means of this beak, which is thrust to 

 its base into the integument, the tick adheres firmly 

 to its host, and in detaching them care must be taken 



that the head be not left behind buried in the skin. 



/ 



The species /. ricinus is commonly found in all stages MOUTH ORGANS OP SHEEP TICK. 

 of growth (see a, , c, d, e,f of figure) adhering to c - capituium; d, e, f, f . segments of 



palp ; i. Spiny beak, formed by 



cattle. The females pump themselves full of blood, f use d mandibles. 



and swell up to the size of a large pea; but the niale 



formerly regarded as a distinct species under the name Reduvius is of smaller 



size, and resembles the empty female in shape. In 

 distribution these pests are almost cosmopolitan, but 

 in tropical countries they reach much greater dimen- 

 sions than in temperate climes, the females sometimes 

 attaining the size of a large gooseberry. In addition 

 to mammals, they attack birds, tortoises, snakes, and 

 lizards; and even the thick hide of the hippopotamus and 

 rhinoceros is of no avail against attack. On account of 

 their numbers, the effects they produce upon cattle are 

 sometimes of a serious nature. These ticks are not, 

 however, found exclusively upon their hosts; they also 

 occur on the ground, and under stones, where pairing 

 and the hatching of the eggs take place. When in want 

 six-iegged young; 



legged young ; c. Male ;<*.*,. .. . , , . 



Female not distended ; e. Fe- shrubs, and clasping the tips of the leaves with their 

 male distended with blood fore-limbs, stand with the other legs stretched out be- 



from below ; /. Same from , . 



above ; g. specimen clinging hind, ready to catch the hairy skin of cattle as they sweep 

 to the hairy integument of through the herbage. Also belonging to this family are 



a mammal. (All figures en- 



ENGUSH SHEEP TICK 



b. Eii 



larged twice. ) 



the genus Argas and its allies, the species of which nearly 



