LIFE HISTORY OF BODY LOUSE 



391 



hair 



--fibres 



Habits and Life History. Although there has been very 

 close association between lice and human beings probably since 

 man's first appearance in the world, little definite knowledge 

 concerning the life history of any of the three species was ob- 

 tained until recently. The importance of lice in the great anti- 

 German war has stimulated much research on them. 



One of the first experiments with the breeding of body lice was 

 made by the great zoological pioneer, Leeuenhoek, in the 17th 

 century. He placed two female lice in his stocking and tied 

 them in; after six days he opened the brood chamber and found 

 a cluster of 50 eggs beside one 

 of the lice and another cluster 

 of 40 eggs, probably laid by 

 the other insect which had 

 escaped. He found 50 more 

 eggs in the remaining louse. 

 He left the eggs in his stocking 

 ten days more, when he dis- 

 covered 25 young lice, where- 

 upon he abandoned his experi- 

 ment in disgust. 



The eggs of lice, commonly 

 called "nits," are oval, whitish 

 objects fitted with a little lid at f lus capitis; 0( f- fff of ^? y ]1 lous f' f- 



humanus. X 25. (After Cholodkowsky.) 



the larger end, through which 



the hatching takes place. The eggs of the body louse are about 

 one mm. ( 5 V of an inch) in length. They are glued to the fibers of 

 clothing (Fig. 175B) especially along seams or creases, although 

 in all other lice the eggs are glued to hair. Under experimental 

 conditions the body louse will sometimes lay eggs on hairs, but 

 it nearly always selects the crossing point of two hairs and shows 

 less skill in attaching the eggs. The body louse shows a marked 

 " homing " instinct in laying her eggs and shows a strong desire to 

 lay eggs where others have been laid, until clusters of from 50 

 to 75 or more have been formed. 



According to recent experiments by Sikora in Germany and 

 Bacot in England, the number of eggs laid by the single female 

 body louse may frequently reach 200 or more. Bacot obtained 

 295 eggs from a single specimen in one case. During the first 

 three or four days only two to four eggs are laid daily, the num- 



FIG. 175. A, egg of head louse, Pedi- 



