lo The Sheep- Scab. 



twelfth day a swelling may be detected with the 

 finger, the skin changes its color and has a green- 

 ish blue tint. During this period the eggs are 

 deposited and are undergoing the process of 

 incubation. The pustule is now rapidly formed, 

 and about the sixteenth day breaks, and the in- 

 sect again appears with its young attached to its 

 legs and covered by a portion of the shell of the 

 eggs from which they have just escaped. Every 

 litter of these parasites comprises according to the 

 best authorities, from eight to fifteen young ones, 

 who set to work to penetrate the neighboring 

 skin, and bury themselves beneath it, where 

 they find their nourishment and grow and prop- 

 agate, until the poor animal has myriads of 

 them preying upon him, and it is not sur- 

 prising that he speedily succumbs under the 

 infliction. 



One female acarus, through the reproduction 

 of its young will give an increase of one million 

 five hundred thousand of progeny in three months, 

 as shown by the following table : — 



