INSECTS: THEIR MOUTHS 173 



there is an exceedingly delicate piece beneath all, which 

 seems to represent the labium or under lip. 



In the active and cunning little Flea, that makes his 

 attacks upon us beneath the shelter of the blankets and 

 under cover of night, the piercing and cutting blades are 

 very minute, and have a peculiar armature. They remind 

 me (only in miniature of course) of those formidable flat 

 weapons which we often see in museums, the rostrums of 

 the huge Saw-fishes (Pristis); a great plate of bone cov- 

 ered with gray skin, and set along each side with a row of 

 serried teeth. Here the blades are similar in form, being 

 long straight narrow laminae of transparent chitine, set 

 along each edge with a double row of glassy points, which 

 project from the surface, and are then hooked backward. 

 These are the mandibles, and they closely fold together, 

 enclosing another narrower blade, the upper lip, which has 

 its two edges studded with similar points, but in a single 

 row. 



In general, as we have seen, the maxillce are the spe- 

 cially armed weapons, the mandibles acting a secondary 

 part, often serving as mere sheaths in those insects which 

 pierce other animals with the mouth. But in this case the 

 mandibles are the favored parts, the maxillce being devel- 

 oped into broad leaf -shaped convex sheaths, enclosing the 

 mandibles. 



There are, however, two cutting blades besides the 

 labial palpi, which have their upper edge thick, divided 

 into four distinct joints, and set with bristles thus retain- 

 ing the proper palpine character, while their under edge is 

 thinned away to a fine keen blade, in which there is no 

 sign of jointing. Then there are the maxillary palpi, of 

 which the joints are furnished at their tips with tiny pro- 



