79 



Mr, J. Boyd gave a demonstration of some parasitic mites. 

 Confining liis remarks to those belonging to the family of 

 tlie Acarea, which are found on man and domesticated 

 animals, and cause the diseases known as Itch, Mange, and 

 Scab. Mr. Boyd explained that these mites belonged to the 

 genera Sarcoptes, Dermatodectes or Psoroptes, Symbiotes, 

 and Demodex. 



On man a species of Sarcoptes and of Demodex are found, 

 the former nausing the itch, the latter inhabiting the seba- 

 ceous and hair follicles, causing the unsightly marks in the 

 skin of the face, popularly called "black-heads." 



On the horse and the sheep a species of Sarcoptes is found, 

 and on the horse, ox, and sheep Dermatodectes affecting the 

 body, and Symbiotes principally confined to the legs, pro- 

 ducing the diseases known as Mange and Scab. 



The dog is subject to two forms of Mange, one caused by 

 a Sarcoptes, the other by the Demodex, wliich appears to 

 be transferable from man to the dog. 



The cat, goat, and pig are subject to the attacks of a 

 species of Sarcoptes. 



Mr. Boyd gave descriptions of the two sexes and larvae of 

 these various mites, and of their ravages on the different 

 animals ujion which they are respectively parasitic, drawing 

 special attention to the serious loss to sheep-owners caused 

 by the "Scab" disease induced by the Dermatodectes, and 

 illustrated his remarks with large diagrams of several of the 

 species, and a number of mounted specimens, which he 

 exhibited under the microscope. 



