l^HE INSECT WORLD. 



*'nits," to the hair; one, Pediculus vestime7iti, found on the 

 body, known as the ' ' body-louse, " or to soldiers as ' ' gray- 

 backs, ' ' lives in and lays its eggs in the seams of clothing, where 

 they are protected ; the last, Phthirius ingzcinalis, known as the 

 "crab-louse," infests the pubic region and armpits. The latter 

 fastens its eggs to the hair among which it lives, and this is per- 

 haps the general rule throughout the series. 



Domestic animals of all kinds are infested by lice ; but it is not 

 necessary to study the species in detail, since their habits are 

 much the same, and the method of treatment is identical. For 

 the head-louse on man nothing is better than a thorough appli- 

 cation of lard, vaseline, or other greasy material. It should be 

 applied at least twice at intervals of a few days, because the treat- 

 ment does not kill eggs, and eggs unhatched at the first treat- 

 ment would not be affected. 



As against the body-louse, the application of mercurial oint- 

 ment in the seams of the clothing answers every purpose. This 

 has proved effective in camps and hospitals, where the insects 

 sometimes increase with marvellous rapidity. 



As against the "crab-louse," the mercurial ointment may be 

 applied directly to the infested spots, and here also several ap- 

 plications are necessary to reach 

 the insects as they hatch from the Fig, 76, 



eggs. Their vitality is great, and 

 that of the eggs is yet greater. 

 Clothing, no matter how carefully 

 washed, may still remain infested 

 with eggs, protected as they are 

 in the seams, unless actual boiling 

 is continued for a considerable 

 period of time. Where lice infest 

 animals the latter can sometimes 

 be cleared by simply giving them crab-iouse, Phtiurius ingumaiis. 

 an opportunity to dust themselves. 



Dogs, donkeys, less frequently horses, and other animals, may 

 be often seen in dusty roads, rolling about in evident enjoyment, 

 and one result of this powdering is a comparative freedom from 

 insect parasites for some time thereafter. Infested animals may 

 be treated as suggested for the head-lice in man, — that is, some 



