Mites Injurious to Domestic Animals. 39 



lesion is diffuse, with intermingling of areas containing hair, and 

 there are here and there numerous blood points. Early cases are 

 difficult to diagnose as there are only a number of pimples, diffusely 

 scattered without loss of hair and which give a positive labial reflex 

 when the part is rubbed." Mr. Fillers affirms that there is a marked 

 seasonal prevalence in sarcoptic mange, the disease being usually 

 at its lowest in warm weather and when there is plenty of sweating 

 of the skin. There is a gradual increase during October, November 

 and the following months, until in March it reaches its height. In 

 the ensuing months it falls slowly, and from June to September 



FIG. 21. 



(a) Tarsus of fourth leg. (b) Tarsus of third leg, of male of 

 Megninia columbae (p. 64), greatly enlarged. (Original). 



the prevalence of sarcoptic mange is at its lowest. It may justly 

 be said to be a disease of winter and long and dirty coats. 



Sarcoptes can usually be found by soaking scrapings from the 

 infected animal in 10 per cent, solution of caustic potash. Occasion- 

 ally, however, it is difficult to find the mites, and it may be necessary 

 to boil the material in the caustic potash and then centrifuge it ; 

 after a few turns of the handle of the machine the Acari are generally 

 to be found at the bottom of the tube. 



Sarcoptic mange should be treated at as early a stage as possible, 



