250 SWINE PRACTICE 



three days moult into nymplia?. The nymphaa have four pairs of legs, 

 but they have no sexual organs. In two or three days the nymphie 

 moult and the sexually matured males and females come forth. The 

 sexually matured parasites mate, and in about three to five days the 

 ovigerous female is found in the gallery in the skin, ovulating. Thus 

 the entire life cycle does not exceed twenty-five days, and under the 

 most favorable conditions may be accomplished in fifteen days. From 

 each ovulation about five males and ten females are produced, and if 

 the reproduction were to go on unhindered for three months, the total 



Fig. 58. Sarccptic mange mite. Female. Magnified 100 times. (Farmers' 

 Bulletin 1085, Dept. Agri.) 



reproduction would approximate 1,500,000 parasites. The adults are 

 mere specks, barely visible to the unaided eye. 



Swine become infested from infested premises or from infested 

 swine. Premises may remain infested for six months or even longer. 



Lesions. — The lesions produced by the Sarcoptes are practically con- 

 fined to the skin ; however, secondary lesions, as emaciation, may arise. 

 The parasite obtains tissue juice by pricking the skin with its stylet. 

 The stylet injury produces erythema, succeeded by the formation of 

 vesicles, which rupture, the vesicular fluid drying and forming a scab 

 beneath which the parasites are found. Scabs are of varying thick- 

 ness, and accumulate wherever the parasites are found unkss the 



