SOME HUMAN PARASITES 



303 



while in the male (Fig. 104) those of the third pair only 

 terminate in bristles, and each one of the fourth pair ends 

 in a sucker. On the anterior end of the body is a strong 

 beak constituting the mouth parts which are formed for 

 piercing and biting. The bodies of the itch mites bear 

 slender bristles of various kinds and lengths. 



It was formerly believed that there were as many kinds 

 of itch mites as there were animals having the disease. 

 Now, however, it is thought that 

 there is only one species and that 

 the itch mites on man, sheep, 

 cattle, goats, and other animals 

 are simply varieties of one and 

 the same species. 



Life history and habits of the 

 mite. — The itch mite inhabits 

 those parts of the body covered 

 with thin skin, especially between 

 the' fingers, and in the bends of 

 the elbows and knees, wrists, and 

 a few other places. The mite 

 excavates tunnels in the skin and 

 lives within these burrows. The burrows usually extend 

 through the outer skin down into the deeper layers of 

 the true skin (Fig. 105). They are more or less tortuous 

 and vary from one-fifth of an inch to over half an inch 

 in length. The female mite may be found at the end 

 of her burrow. Behind her in the tunnel will be found 

 the tiny oval eggs which she deposited as she lengthened 

 the burrow. She finally becomes exhausted, much 

 shriveled, and eventually dies. Braun says, "The six- 

 legged larvse hatch out after four to eight days, and 



Fig. 104. — Itch mite, male. 

 (X 125.) 



