100 



CERTAIN PAUASITIC IXSECT8. 



sucker of the Pediculus, to the stout chitiuous jaws of the 

 Mallophaga, or bird lice, is a sudden trausition, but on com- 

 paring the rest of the head and 

 body it will be seen that the dis- 

 tinction only amounts to a family 

 one, though Burmeister placed the 

 Mallophaga among the Orthoptera 

 (grasshoppers and cricliets) on 

 account of the mandibles being 

 adapted for biting. It has been a 

 common source of error to depend 

 too much upon one or a single set 

 of organs. Insects have been classi- 

 fied on chai'acters drawn from the 

 wings, or the number of the joints 

 , of the tarsi, or the form of the 

 mouth parts. We must take into 

 account in endeavoring to ascer- 

 tain the limits of natural groups, 

 all the organs collectively, as well 

 as the internal anatomy and the 

 embryology and metamorphosis of 

 insects, before we can hope to 

 obtain a natural classification. 

 The family of bird lice is a very extensive one, embracing 

 many genera, and several hun- 

 dred species. One or more spe- 

 cies infest the skin of all our 

 domestic and wild mammals and 

 birds, some birds sheltering 

 beneath their feathers four or 

 five species of lice. Before giv- 

 ing a hasty account of some of 

 our more common species, we 

 will give a sketch of the embryo- 

 logical history of the lice, with 

 special reference to the structure 

 of the mouth parts. . 



The eggs (Fig. 114, egg of the head louse) are long, oval, 

 somewha" pear-shaped, with the hinder end somewhat pointed, 

 while the anterior end is flattened, and bears little conical micro- 



lli. Embrj'O of the T.ouse. 



-max' 

 115. Mouth Parts of the Louse. 



