PARASITIC DISEASES. 



155 



the progeny of a single pair of mites may at- 

 tain to the astounding number 150,000,000 in 

 about four months ! 



Symptoms: To the experienced, the symptoms 

 of scab are very plain. When a sheep becomes 



SIIEKP-SCAB MITE (Psoroptcs ovis). Male. 

 Dorsal view greatly enlarged. 



(After Salmon nnd Stiles, 1S9S.) 



infested with one or more mites, small inflamed 

 zones occur where the mite pierces the skin to 

 obtain food. This is followed by itching and the 

 formation of papules, and, as the mites multiply 

 in numbers, the area of inflammation rapidly 



