158 INSECTS 



The crab louse is treated by local applications of 

 mercurial ointment or by tincture of larkspur (Del- 

 phinium), the latter of which is also used against the 

 head louse. 



The habit that some savages have of covering them- 

 selves with grease, oil or paint, is not entirely without 

 practical advantage, for thereby they do undoubtedly 

 keep themselves measurably free from these parasitic 

 forms. The use of ants to rid infested clothing of para- 

 sites is referred to by Mark Twain in his inimitable 



way, and it was a recognized 

 practice in the far west in 

 olden days, when changes of 

 clothing were not readily ob- 

 tainable, and when lodgings 

 and lodgers could not be 

 chosen but had to be ac- 

 cepted as found. It meant 

 simply stripping naked, and 

 FIG. 66. Crab louse of man. placing all the clothing on 



an ant hill, where it would 



be immediately invaded by the ants anxious to attack 

 and destroy every living thing on or in this foreign 

 material. In a short time the clothing could be again 

 put on with the comforting assurance that it was at 

 least temporarily free. 



Most of our hairy domestic animals are subject to 

 the attacks of similar parasites, each of which lives 

 and propagates on the body of its respective host. 

 Spread from one animal to another occurs when they 

 are in contact in stables, or herded closely together for 

 shade in the pasture. Sometimes a parasite leaves 

 its host voluntarily or is rubbed off by it in the stable, 

 kennel or field. It may then crawl about on woodwork, 

 plant or tree, hiding in crevices until another host 



