166 



CIVIC BIOLOGY 



relief, if applied soon after exposure and before the mites 

 have become embedded in the skin. 



Itch mites — Sarcoptes scabiei {scabere, *^ to scratch '»). These 

 mites have long been a terror to man. They multiply at the 

 rate of 15,000,000 from a single pair during the season, are 

 easily passed from one animal to another, and are extremely 

 difficult to control. There are many varieties of itch mites, 



differing in size ac- 

 cordmg to the thick- 

 ness of skin of the 

 animal they attack. 

 The pig, horse, wolf, 

 goat, camel, sheep, 

 doo; — each has its 

 own variety (de- 

 creasing in size in the 

 order here given) 

 and the human mite 

 is the smallest of all. 

 The punctures made 

 in the skin bv mites 

 are soon covered 

 with a crust, the eggs 

 bemo- found beneath 

 it. The human mite 

 is best held in check by warm baths with free use of soap 

 followed by an application of sulphur ointment. The same 

 treatment is equally good for dogs. 



Sheep-scab mite. — Psoroptes communis (var. ovis). This para- 

 site is distributed over the entire world and has proved so 

 destructive that most countries have passed laws to prevent 

 its importation or spread. With intelligent cooperation in the 

 use of precautions and methods of treatment now understood, 

 sheep scab could soon be eradicated. 



Fig. 81. Egg cocoons of spiders on burdock 

 Photograph by Dr. J. P. Porter 



