114 Veterinary Medicine. 



Adult Males, smaller and flatter than the females, but with 8 

 legs. 



Adult (replete ovigerous) females, 8 legged ; fully developed 

 oviducts containing eggs. Fasting are flat and leathery, but 

 soft and rounded when full of blood. 



Each tick is naturally divided into head and body. 



I. Head {capitulum). This consists of the base, 2 mandibles, 

 dart and 2 palpi. 



The base of the capitulum {mouth shield) is a hard, solid 

 segment, usually transversely elongated, and inserted into a notch 

 on the anterior border of the dorsal shield and body. Anteriorly 

 it supports the other elements of the head — the mouth organs. 

 On its upper surface, in females, it bears two porous aregs {arecB 

 poroses'). 



The mandibles {jaws, chelicerce), right and left, thickened at 

 the base, slightly narrowed toward the free ends, lie above the 

 dart, and are each terminated by a digit bearing from one to four 

 hooks recurved dorsally, like a harpoon. 



The upper surface of the mandibles is sometimes covered by a 

 thin mandibular sheath having its exposed surface roughened 

 like a file. 



The dart {hypostome, labium, tongue, radula) lies beneath the 

 two mandibles and is best seen from below. It is somewhat flat- 

 tened, has a bilateral symmetry, and is covered, more or less per- 

 fectly beneath {ventrally) or even laterally by hooks {teeth 

 denticles) which are recurved toward the body. Near the point 

 of the dart these teeth are small and irregular, but farther back 

 they are larger and are arranged in rows, longitudinal and trans- 

 verse, the numbers of which are important for identification of 

 species. 



The jaws, mandibles and mandibular sheaths when brought to- 

 gether form a central canal or tube through which the blood is 

 sucked. The whole mass is inserted into the tissues and firmly 

 held there by the barbed surface, and has been given the names 

 of beak, rostrum, proboscis or haustellum. 



The palpi, which with the above complete the structures of the 

 head, are two organs, each formed of 4 articles, placed to the 

 right and left of the beak. 



