LINGUATULA RHINARIA 



349 



and there encyst (Fig. 146D). After a series of moults a second 

 larval stage is entered upon, this time with a wormlike appear- 

 ance much more like that of the adult (Fig. 146E). 



At this stage a " wanderlust " seizes the tongue- worm and it 

 begins an active migration in an endeavor to reach a more satis- 

 factory site for adult life. The mites may settle in the res- 



FIG. 146. Life history of tongue- worm, Linguatula rhinaria; A, adult female 

 from nasal passage of dog; B, egg containing embryo; C, larva from sheep, man or 

 other animals; D, encysted larva; E, 2nd larval stage, from liver of sheep or man. 



piratory tract of their original host, or may abandon their host 

 by way of throat or anus to take chances on being snuffed up or 

 taken into the mouth cavity of another animal. Having gained 

 access to their final habitat in the nostrils or lungs, they attach 

 themselves by their hooks, moult, copulate and reproduce. 



While both larval and adult stages of tongue-worms are oc- 

 casionally found in man, the larvse, as liver parasites, are more 

 common. 



The tongue-worm most frequently observed in man is Lingua- 

 tula rhinaria. The male of this species is a small worm, whitish 

 in color, about three-fourths of an inch in length, whereas the 

 female (Fig. 146 A), which is yellowish or brownish due to the 

 eggs in her body, reaches a length of from three to five inches. 

 The adults occur most commonly in the nasal passages of dogs 

 (Fig. 147). The eggs (Fig. 146B) are dispersed with mucus 

 during the violent fits of sneezing to which the presence of the 

 parasite gives rise. The swallowing of food or drink, especially 

 grass or vegetables, soiled by this infective mucus, results in the 

 access of the larva-containing eggs to the intermediate host, which 

 is most frequently sheep, goats, rabbits, etc., but occasionally 



