DISEASES CAUSED OR CARRIED BY MITES AND TICKS 407 



The mites form a crust of dead skin on the legs of the chickens (plate 

 XXIV). The related species, Cnemidocoptes gaUinae Railliet, causes the 

 hens to pluck their feathers. The mites work at the base of the feathers 



Plate XXV. — Dipping scaly legs of chicken in crude oil (Bishopp.) 



and are called depluming mites. These mites are controlled by dipping 

 in crude petroleum (plate XXV). 



DEMODECTIC ^lANGE, when caused by Demodex folliculorum 

 Simon, gives rise to BLEPHARITIS, SEBORRHEA or BLACK- 

 HEADS. Many animals and man are attacked by this mite. Probably 

 a majority of persons harbor this mite. Demodectic mange is a common 

 and practically incurable disease in dogs. Demodex phylloides Csoker 



