THE PEDICUU. 409 



structural details. Then the parasite is born closely resembling 

 its parents. 



There are two great divisions of the Anoplura ; in one, the true 

 lice, the insects have suckers ; and in the other, the bird lice, there 

 are jaws. The Pcdiadi which are parasitic upon the hair and 

 clothes of man are, of course, disgusting on account of their asso- 

 ciation with dirt and disease, but nevertheless they are interesting 

 creatures to the naturalist, on account of their wingless and 

 degraded condition, as well as from their not undergoing meta- 

 morphosis. Moreover, there is much interest accompanying their 

 birth, for the females preponderate, and they can lay fertile eggs 

 time after time without the help of the male, and generations of 



Philopterus selcifrons. Pedictilus capitis. 



females succeed each other and produce fertile eggs under the 

 same exceptional circumstances. 



The Head Louse, drawn above, is not very unlike a long bed- 

 bug {Cimcx) in its early stage. 



The lice without suckers, and with jaws that can bite through 

 the skin, afflict most domestic mammals and all sorts of birds. In 

 tracing their development within the tgg it becomes evident that 

 some of the earlier characters of the embryo are retained per- 

 sistently ; thus the permanently enlarged forehead of the bird louse 

 can be recognised during very early egg life, but this structure 

 disappears very soon in the embryos of the true lice with suckers. 



The legs and claws of the different species of Plnlopteroiis or 

 bird lice vary much in structure, on account of the peculiar con- 

 ditions in which the parasites are placed and live. One genus, 

 which has a species parasitic on the porpoise — the only marine 



