348 THE MITES 



Demodex infection, but it is probable that sulphur applications 

 in some form would reach and destroy them. 



Tongue-worms 



Related to the mites, but now placed in a distinct order, Lin- 

 guatulina, are the tongue- worms. These animals have become so 

 modified by parasitic life that the adults have lost nearly all re- 

 semblance to the other members of their group, and have become 

 so wormlike, both in form and life history, as 

 to have been classified by older writers with 

 the tapeworms (Fig. 146A). Only the larval 

 stage gives a clue to their real relationships. 

 Their long bodies are either flattened or 

 cylindrical, and distinctly divided into rings 

 or segments as in leeches. There is no dis- 

 tinct demarcation between head, thorax and 

 abdomen. On either side of the mouth are 



of ^Porocephaius wmti- two hooks which can be retracted into grooves 

 latus. x 3. (After like the claws of a cat (Fig. 145) . These are 

 usually looked upon as the vestiges of some of 

 the appendages. At the bases of the retractile hooks there open 

 a number of large glands, the secretion of which is believed to have 

 blood-destroying power. The internal organization of the body 

 is degenerate in the extreme; there is no blood, no respiratory 

 system, no special sense organs, no organs of locomotion; little 

 more than the barest necessities of racial existence a simple 

 nervous system, a digestive tract and a reproductive system. 

 The sexes are separate. 



The adult worms live in the nostrils, trachae or lungs of car- 

 nivorous reptiles and mammals, where they produce their myriads 

 of eggs. The latter are voided with the catarrhal products of 

 the respiratory system caused by the presence of the parasites. 

 The egg-laden mucous excretions from the nose of an infected 

 animal are dropped on vegetation and eaten by herbivorous ani- 

 mals, whereupon the eggs (Fig. 146B) develop into larvae in the 

 new host. These larvae (Fig. 146C), hatched out in the stomach, 

 are far more mitelike than the adults, inasmuch as they possess 

 two pairs of rudimentary legs and primitive arthropod mouth- 

 parts. The larvae migrate to the liver, spleen or other organs 



