RELATION TO OTHER ANIMALS 159 



animal comes into such a position as to enable it to 

 crawl among the hair or wool. 



As uncivilized man greases or paints himself, so 

 animals have developed a method for securing freedom 

 from parasites: they dust themselves or coat them- 

 selves with mud. The spiracles of most lice are not well 

 protected, so when animals get into a dusty road and 

 roll about, this serves a very practical purpose and 

 those that get into a mud hole and wallow are often 

 seeking similar relief. Other species of Hemiptera 

 preying upon man will be considered under the heading 

 of household pests. 



Besides the sucking lice belonging to the order 

 Hemiptera, many animals and most birds are also sub- 

 ject to the attacks of biting lice, belonging to the order 

 Mallophaga, which means, literally, wool-eaters, and 

 is somewhat misleading. Commonly they are also 

 known as "bird-lice" because they very usually infest 

 the feathered tribe. In color and appearance they do 

 not much differ from the sucking lice; but the head 

 is usually more blunt, and instead of puncturing the 

 skin and living on blood, they have mouth parts formed 

 for chewing and biting, and live rather on the surface 

 scales and scurf at the roots of the hair and feathers. 

 They do not puncture the skin to reach blood, but will 

 feed on clotted blood at the edge of any wound and may 

 prevent healing, or even cause the extension of a sore 

 spot. And so, while a few individuals on the skin 

 cause little inconvenience or unpleasant effect, yet 

 when a great number are at work, the feeding at the 

 base of the hair and of the smaller feathers results in 

 the death of these out-growths and the infested animal 

 becomes "mangy" in appearance. The true mange 

 is, of course, due to a mite parasite of quite a different 

 kind; but that "mange" which consists of bare spots 



