CHAPTER XVI. 



ExTERNAiv Parasite;s. 



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 surface of the skin and upon the feathers, 

 deriving their nourishment 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 dis- 

 eases. 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 Qgg 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 physi- 

 ology of a bird as it is to that of a man. 



Keeping a Poultry Plant Free from External Parasites. 



It is not necessary for a poultryman to be able to distinguish 

 the 32 species of parasites or to know their life histories in order 

 to keep his plant free from them. It is only necessary to know 

 that some of them stay on the birds and can only be extermi- 

 nated by treating the birds (usually with a powder) while others 

 spend most of their time on the under sides of the roosts in 

 cracks and can best be exterminated by contact sprays contain- 

 ing cresol or kerosene. A single application is not efficient in 



