BURROWING-MITES. 53 



body; the ambulatory suckers are carried on a long tri- 

 articulated pedicle; the male has copulatory suckers and 

 abdominal prolongations. 



3. Sucking* Itch-mites (Symbiotes), which live only 

 upon the surface of the skin, but which penetrate with their 

 mandibles through the upper skin to suck blood, lymph and 

 serum. Usually they can not thrive upon the human skin, 

 though cases have been reported in which species infesting 

 sheep invaded successfully another host, man. 



These mites have an oval body; beak slightly conical, as 

 wide as long, and destitute of cheeks; the legs long, thick, 

 and visible beyond the sides of the body; the ambulatory 

 suckers are very wide and carried at the end of a siinple and 

 short pedicle; the male has copulatory suckers, and more or 

 less developed abdominal prolongations. 



1. Burro will g'-mites (Sarcoptes). — This genus con- 

 tains two sub-genera, one infesting mammalia, the other> 

 birds. The former contains two species, the common itch- 

 mite {Sm'coptes scah/ei De Geer), and the dwarf itch-mite 

 ( Sar copies minor Fuers t . ) . 



The common itch-mite {Sarcoptes scahiel De G.) is found 

 on man and on a large number of mammals, where it causes 

 the ordinary itch or mange. The parasite varies according 

 to the species of mammals upon w^hich it lives, and not alone 

 in dimensions, but even in secondary anatomical details. 

 Formerly these varieties were described as so many species. 

 The following varieties are found upon our domesticated 

 animals: 



MANGE OF HORSE {S. scaUei^sx. equi). 

 SCAB OF SHEEP {S. scableiYHY. ovis). 

 SCAB OF GOAT {S. scahiel yqx. ccqme). 

 SCAB OF PIG {S. scahiel var. sids). 

 MANGE OF DOG {S. scahiel xar. canls). 

 MANGE OF WOLF {S. scablel rar. I ujn). 



According to Fuerstenberg this last variety causes the 

 Norwegian itch mentioned later. 



