Lice and Filth 331 



species which are very troublesome to chicken- 

 raisers, particularly to those who do not keep 

 their poultry-yards and -houses in a cleanly con- 

 dition. Filth and dampness seem to favor the 

 propagation of these pests. Fowls are naturally 

 cleanly, particularly those that have their liberty 

 and, consequently, live under conditions nearest 

 the natural ones. Weak fowls are always more 

 likely to be troubled with lice than are strong, 

 healthy, vigorous ones. Many years ago it was 

 thought that filth and dampness produced lice. 

 While these conditions undoubtedly favor the 

 increase and development of these pests, yet they 

 can only be produced in a flock by the introduction 

 of an infected bird or by placing the fowls in infected 

 quarters. The life-history of these parasites is 

 so well known that it is not thought possible for 

 them to be introduced in any other way. The 

 species of lice which infest chickens vary consider- 

 ably as to their shape and size, yet in their habits 

 they closely resemble each other. They are very 

 small insects, varying from one-fifth to less than 

 one-fiftieth of an inch in length. These parasites 

 rarely pierce the skin and suck the blood, as do 

 mites and fleas. They cause much annoyance by 

 crawling over the surface, and sometimes they 

 bite the skin in a way that causes considerable 

 irritation and perhaps some inflammation. When 

 fowls are once infested they may become unthrifty 



