58 



THE AMERICAN MONTHLY 



[Feb., 



clasping, noted especially in the liog louse in which the 

 end of the tibia is a protractile disk which presses against 

 the hair. The abdomens are large, the spiracles prom- 

 inent and in some s])ecies there is a peculiar brush-like 

 organ on the under side. 



The function of this organ is unknown and hitherto no 

 suggestion has been made as to its office. It would seem 



probable that it serves to retain the abdomen in a ])ro- 

 per position for the deposition of eggs, the hair to which 

 the insect is attached being held between these two brushes. 



The characters most used in classification are, the form 

 of head, the number of joints in the antennys, the form of 

 sternal plate and of abdomen, tlie structure of the tarsi 

 and the special appendages on antennsB, legs and abdomen. 



The MallophagidfP are classified mainly on modifica- 



