CHAPTER XV 



External Parasites 



Vigilant and continuous attention is necessary to keep 

 fowls free from external parasites. At least 32 species of 

 arachnids and insects are known to be parasitic on fowls. 

 Some of these like the red mites visit their host only to take 

 food and spend the rest of the time on the under side of the 

 roosts, in cracks and crevices and various other places of 

 seclusion. Others like the lice normally stay on the birds, 

 although occasionally some individuals crawl off, especially 

 into the nest."^ Some of these parasites live upon the sur- 

 face of the skin and upon the feathers, deriving their nourish- 

 ment either by sucking the blood like the red mite, or by 

 chewing the skin and feathers like the lice and some of the 

 mites. Some of the mites, however, bore under the skin, 

 causing skin diseases known as scabies or psoric diseases. 

 The most common of these diseases are scabby or scaly leg 

 and depluming scabies. 



The economic importance of these external parasites is 

 very great. Fowls infested with one or several of these 

 species of parasites are not profitable. They make a smaller 

 growth in the same time with the same food and their egg 

 production is not equal to similar birds not so infested. 

 Not only are they constantly robbed of some of their tissue 

 and blood but their rest is disturbed. Sleep is as important 

 to the normal physiology of a bird as it is to that of a man. 



Keeying a Poultry Plant Free from External Parasites. — 

 It is not necessary for a poultryman to be able to dis- 

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