1 28 AOARINA OR MITES. 



The metamorphosis is as follows : — 



The Larval or first stage is a small acarus with only three pairs 

 of legs and no genital organs, and with two long anal hristles. 

 The larva moults two or three times. Then follows the second 

 or Nymph stage. The Nymph has a fourth pair of legs, which 

 are, however, small. As yet no sexual organs are to be found. 

 We observe two sizes of nymphs ; the small ones will be males, 

 the large females. Casting their skin, both males and females 

 are produced, and then copulation takes place. They are then 

 known as pubescent males and females. The male soon dies ; 

 but the female undergoes another moult, and becomes the 

 ovigerous female, with a sub-thoracic vulva, and then deposits 

 about fifteen large ova. Gerlach states that one female, having 

 given rise to six generations, is accountable for 1,500,000 

 individuals in about ninety days. 



The Sarcoptes have a rounded body. The posterior legs are 

 very small, and nearly or quite concealed beneath the body. 

 The ambulacral sucker is in the form of a simple long pedicle. 

 The females deposit their eggs at the bottom of the furrows they 

 excavate in the sub-epidermic tunnels. Pgoi-opies have a more 

 oval body, all the legs are visible, and the ambulatory suckers 

 are borne on large three-jointed pedicles. The psoroptes do not 

 make sub-epidermic galleries, but live in societies amongst the 

 crusts they cause on the skin. Symbiotes are oval, and have all 

 the legs visible outside the body margin, with the claws borne 

 on a broad, short, and simple pedicle. These live like psoroptes 

 in colonies under the scabs, and cause more localised patches 

 than the others. 



Each domestic animal has a variety common to it ; but it is 

 said that the itch of man can be taken by the dog and other 

 animals, a point which cannot be accepted as proven. The 

 sarcoptic mange of the horse, however, can be easily transmitted 

 to the ox. Kegarding the transmission from one animal to 

 another and man, there is much diversity of opinion. 



