158 SUPPLEMENT TO THE ORDERS 



nourish several. Man, as we have already seen, is attacked 

 by three species. 



Swammerdam, who has given us the anatomy of the human 

 louse, was unable to discover any male among those which 

 he examined. He always found in them an ovary ; which 

 occasioned him to suspect that they were hermaphrodites. 

 But the observations of Leeuwenhock, differ much from 

 those of that author. He has observed individuals among 

 these insects provided with all the parts which characterize 

 the male sex, and he has given the figures of those parts. 

 The same author has also discovered in those which he re- 

 gards as males, a recurved sort of sting, situated under the 

 abdomen, with which, according to him, they can prickle. 

 He believes that the great itching which they occasion 

 proceeds from the pricking of this sting, having remarked 

 that the introduction of their proboscis into the flesh pro- 

 duces scarcely any sensation, unless perchance that it touch 

 on any of the nerves. Degeer tells us, that he has seen a 

 similar sting situated at the end of the abdomen in several 

 human lice as well those of the body, as of the head. The 

 individuals, which according to the opinion of Leeuwenhoek 

 are the males, have, according to Degeer, the end of the ab- 

 domen rounded, whereas the females, or those which have no 

 sting, have it emarginated. M. Latreille has also observed, 

 very distinctly in a great number of individuals, the sting, 

 or at least the conical and scaly point of which the aforesaid 

 authors have made mention. 



The multiplication of these insects is unfortunately far too 

 great, but they are not quite so prolific as some have repre- 

 sented. Experiments have proved that in six days a louse 

 can lay fifty eggs, and that some will still remain in the 

 belly. The young ones soon issue from the eggs, (at the end 

 of six days,) and change their skin several times, after which, 

 they are in a state to reproduce. This occurs about eighteen 



