ARTHROPODS 



195 



The adult is believed to be a Porocephalus which lives in 

 snakes, pythons, in the lungs, possibly the Porocephalus 

 constrictus. 



Demodex folliculomm. A nearly legless degenerate 

 acarine which lives in the hair follicles and sebaceous 

 glands of man and other animals. They are seen as 

 black points around which there is a variable, frequently 

 a negligible, amount of inflammation. They may, when 

 numerous, cause a severe dermatitis. Such a dermatitis 

 is more common in the lower animals. The small eleva- 

 tions surmounted by a black spot, so commonly found 

 in man and termed comedones, often contain this 

 parasite. 



FIG. 74. Demodex folliculorum of the dog. (After Megnin.) 



The females are 0*38 mm. in length and 0*045 m m. in 

 breadth at the thorax. There is a rostrum, a fused 

 cephalothorax with four pairs of legs which are very 

 short, but composed of three joints. The abdomen is 

 elongated, conical, and striated transversely. The anus 

 is on the ventral surface (fig. 74). The males are smaller 

 and the abdomen shorter. 



