INSECTS INJURIOUS TO DOMESTIC ANIMALS, ETC. 671 



in different directions like the spokes of a wheel. The entire 

 life is spent on the host and the life cycle requires about two 

 weeks. Multiplication is rapid. 



Symptoms include a roughened condition of the coat on the 

 infected areas, this gradually spreading all over the body and 

 being followed by shedding of the hair and a scabby appearance 

 of the skin, caused by the burrowing of the mites and the conse- 

 quent irritated condition. 



Control of scabies is secured through the use of dips. Of 

 these the lime-sulphur compounds are recommended, since they 

 kill all the parasites which may be on the animal. Dipping will 

 be discussed separately since it is the treatment recommended 

 for several of the parasites of stock. 



Sheep Scab * 



The organism causing the sheep scab is merely a variety of 

 the one causing the scab of cattle, Psoroptes communis ovis, 



FIG. 591. Sheep infected with scabies. Early and late stages. Ky. Agr 



Exp. Sta. 



being the name for the sheep scab organism and P. communis 

 bovis, being responsible for the cattle scab. A third variety 

 P. communis equi, causes the scab of horses. 



The life history of the sheep scab mite is the same as for 

 * See Marion Imes, Farmers' Bulletin 713, U. S. Dept. of Agr. 



