DISEASES OF POULTRY. 205 



The birds occasionally peck at or scratch the affected 

 parts with the beak. They do this most frequently 

 at night and in warm weather. 



Causation. — Scaly legs is a form of scabies or 

 mange caused by the mite known as the Sarcoptes 

 mutans. It is a strictly contagious disease although 

 it does not spread rapidly from bird to bird, and there 

 may be only a few noticeably affected birds in a flock. 

 The Asiatic breeds are most 

 susceptible to it, and many 

 birds, even of these breeds, 

 resist the attacks of the mites, 

 and never show any symptoms. 

 It attacks quite a variety of 

 birds — fowls, turkeys, pheas- 

 ants, partridges and cage 

 birds, but has not been ob- 

 served in ducks and geese. In 

 the production of scaly legs, 

 the Sarcoptes mutans penetrates Fig-. s<).—Sarcoptes mutans of 



* .1.1 • i • 1 the fowl: ovifferous female; 



beneath the epidermic scales dorsal surface; magnified 100 



on the upper surface of the '^"^ ^'^^' 

 foot and the front of the shank, and by burrowing there 

 sets up an irritation which leads to a multiplication of 

 the cells of the part, and an exudation of serum. It 

 is by the union of these two products that the white, 

 powdery crust' is formed, which raises the epidermic 

 scales from their normal position. If the crusts are 

 removed and the under surface examined with a lens 

 they are found to contain a large number of depres - 

 sions in each of which a female, egg -containing Sar- 

 copt is lodged. The larvae, males and younger females 

 are found wandering beneath the crusts. The crust 

 contains so many cavities that it has very much the 



