THE TICKS d 



Order II. Lixguatulida 



15S 



Arachnida (p. 94). — The iiiombers of this group are arachnids which 

 have become extremely altered in consequence of their parasitic mode 

 of life. Due to their worm-like body and endoparasitic habits, they were 

 formerly placed with the helminths. 



The body is elongated, annulated, and somewhat flattened. The 

 bodj' regions are not defined from each other. With the exception of 

 two pairs of articulated hooks 

 surromiding the mouth, re- 

 garded by some as vestigial 

 legs, the adult body is entirely 

 without appendages (Fig. 83). 



The mouth is anterior, and 

 the intestine passes directly 

 through the body, opening by 

 the posterior anus. 



There are no circulatory or respiratory organs 

 general surface of the bod.y. 



The nervous system is reduced, consisting of the esophageal ring, 

 which gives off filaments to the cephalothorax region. Eyes are absent. 



The sexes are separate; the male much smaller than the female. From 

 the eggs there hatches an ovoid embr^'o, constricted at its posterior 

 extremity, and provided with two pairs of jointed legs. Anteriorly it 

 has a perforating apparatus by means of which it bores through the 

 intestinal wall of its host and reaches the liver, or other organ, in which 

 it becomes encysted. 



The adult Linguatula (L. rhinaria) infests the nasal cavities of mam- 

 mals, usually the dog. The larvae infest the visceral organs of herbivor- 

 ous animals. 



Fig 83. — Linguatula rhinaria, adult (after 

 Osborn, from Packard; Bull. No. 5, Bureau of 

 Entoniologj-, U. S. Dept. of Agr.). 



Respiration is by the 



