36 



Insects and Disease 



that his skin has not had the care it should have. 

 Very recently certain investigators have found that 

 the leprae bacilli are often closely associated with 

 these face mites and believe that they may possibly 

 aid in the dissemination of leprosy. It is also 

 thought that they may sometimes be the cause of 

 cancer, but as yet these theories have not been 

 proven by any conclusive experiment. 



In dogs and cats these same or very similar 

 parasites cause great suffering. In bad cases the 

 hair falls out and the skin becomes scabby. 

 Horses, cattle and sheep are also attacked. The 

 disease caused by these mites on domestic animals 

 is not usually considered curable except in its very 

 early stages when salves or ointments may help 

 some. 



Itch-mites. "As slow as the seven-years' itch" 

 is an expression, the meaning of which many could 

 appreciate from personal experience, for it certainly 

 seemed to take no end of time to get rid of the itch 

 once it was contracted. Just why seven years 

 should have been set for the limit of the disease is 

 not clear, for if the little roundish mites that cause 

 the disease live for seven years on a host they are 

 not going to move out voluntarily even if their 

 seven-year lease has expired. 



The minute whitish mites (Fig. 20) that cause 



