_Depluming scabies_ is caused by _Sarcoptes laevis var. gallinae_. This mite causes the feathers to break off at the surface of the skin. Masses of epidermic scales may form around the broken ends of the feathers. The diagnosis can be confirmed by examining the skin lesions and finding the mite. _The air sac mite_ (_Cytodites nudus_) may cause sufficient irritation to the mucous membrane lining the air sacs to seriously obstruct the air passages with mucus, or produce death from exhaustion. A post-mortem examination of a fowl that has died of this disease shows the mites on the surface of the lining membrane of the air-sacs. They appear as a white or yellow dust. TREATMENT OF POULTRY DISEASES CAUSED BY MITES.--Diseases of poultry caused by mites may be prevented by quarantining all recently purchased birds for a period of from two to four weeks, and by keeping the poultry houses clean. Birds that are found infested with parasites should be destroyed or returned. In case the bird is valuable and suffering from external parasites only, it should be given the necessary treatment. _Red mites may be destroyed_ by thoroughly cleaning the poultry house, and spraying the roosts, nests, walls and floor with a three per cent water solution of liquor cresolis compositus. This should be repeated twice a week for two weeks. _Scaly-leg may be treated_ by applying a penetrating oil to the feet and lower part of the leg. It is advisable to first remove the scales by scrubbing the part with soap and warm water. Dipping the feet in a mixture of kerosene one part and linseed oil two parts is recommended. This should be repeated as often as necessary. QUESTIONS 1. Describe the different bot-flies. 2. Give the life history of the bot-fly of the horse; of the ox; of sheep. 3. Give the symptoms of bot-fly diseases. 4. Give the symptoms of lousiness. 5. Give treatment for lousiness of different farm animals. 6. What is the damage from the sheep-tick? Give treatment. 7. Describe the injury from scabies and mange. 8. Give treatments for these diseases. 9. Mention the several poultry mites and tell how to treat them. CHAPTER XXV ANIMAL PARASITES The common parasitic diseases of domestic animals are caused by the following groups of worms: _Flukes_ or _trematoides_; _tapeworms_ or _Cestoides_; _thorn-headed worms_ or _Acanthocephales_; and _round-worms_ or _Nematoids_. Flat worms, such as tapeworms and flukes, require secondary hosts. The immature and mature forms of tapeworms are parasites of vertebrate animals, but an invertebrate host is necessary for the completion of the life cycle of the fluke. The hog is the only specie of domestic animals that becomes a host for the thorn-headed worm. The round-worm is a very common parasite. There are many species belonging to this class. [Illustration: FIG. 70.--Liver flukes.]