Lice and Filth 309 



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. 

 Lice can be produced only by the introduction of 

 an infected bird or by placing the bird 'in in- 

 fected quarters. The life history of these para- 

 sites 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 considerably 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 and 

 unprofitable if not given proper care. It has 

 been estimated that a single pair of lice may pro- 

 duce, through the quickly successive generations 



