32 LICE AND THEIR MENACE TO MAN 



skin of the lower surface of the body. The 

 inverted bag of the male is now everted, rolling 

 inside out into the vagina of the fernale, and the 

 spermatozoa pass through the small penis, which 

 is thus thrust well into the vagina, and fertilisa- 

 tion is effected. 



The eggs are laid at the rate of eight to ten a 

 day, and this continues for twenty-five to thirty 

 days, so that each pair of lice produce about three 

 hundred offspring of the first generation, and 

 many of these will have started to breed before 

 their parents die. Bacot (3) states that a female 

 louse under conditions ideal from her point of 

 view might have about 4000 offspring during her 

 lifetime. Conditions would of course never be 

 ideal. Some of the eggs w r ould probably fail to 

 hatch, and many of the young would die from 

 one or other of the many catastrophes which are 

 liable to befall the louse. As an actual instance 

 of breeding capacity the following may be quoted. 

 Into one of the small experimental boxes used in 

 the laboratory a hundred young larval lice were 

 placed. The box was about three-quarters of an 

 inch in diameter and of the same depth. It had 

 a glass bottom, while the other end was covered 

 with chiffon, through which the lice could not 

 escape but could easily feed. The insects were 

 fed twice daily by being bound on to the forearm 

 for half an hour for each feed. Between their 

 meals they were kept in an incubator at a tempera- 

 ture of 86 F. After forty days the box was 



