322 BIOLOGY: GENERAL AND MEDICAL 



numerous the victim suffers considerable malaise 

 and some elevation of the body temperature. 

 As the weals form, the bodies of the mites 

 become surrounded by the tumefied skin and 

 appear as minute transparent red points at 

 the centres of the weals. The life history of 

 these mites is not completely known. 

 The ticks and mites are not all parasitic upon 



FIG. 116. Leptus autumnalis. (After Trouessart.) 



warm-blooded animals; a few infest snakes, 

 reptiles, and even fishes. 



A peculiar arachnid, probably related to the 

 mites, the Liguatulid, is parasitic upon the 

 tongue of dogs. 



Phylum Chordata. Of the vertebrates there are very 

 few parasitic representatives. 



Class Pisces. The Hag-fishes may with pro- 

 priety be classed among the parasites. The 

 common hag, Myxine glutinosa, is an eel-like 

 fish, not infrequently 18 inches in length. 



