INSECTS : TIIEIE MOUTHS. 169 



SO delicate, that twelve of them are cut in the length of 

 a ten-thousandth part of an inch ; and yet they are 

 quite regular and symmetrical in length, height and 

 form ! I know of no structure of the kind which equals 

 this. These teeth are continued throughout the inner 

 edge of the blade from the tip to the base, and are 

 about eight hundred in number ; though the length of 

 the entire blade is only such that upwards of a hundred 

 and fifty of them, if laid end to end, would not reach to 

 the extent of an inch ! 



The office of these wonderful instruments is doubt- 

 less to cut and enlarge the wound within, and thus pro- 

 mote the flow of blood. The whole apparatus is 

 plunged into the flesh of the victim — ^horse or man ; 

 then the maxillce expand, cutting as they go, and doubt- 

 less working to and fro as well as laterally, so as to saw 

 the minuter blood-vessels. At the same time the man- 

 dibles, with their saw-teeth on one side, and pricking 

 points on the other, work in like manner, but seem to 

 have a wider range. Finally, 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 mu- 

 seums, the rosi/ruTTis of the huge Saw-fishes {Pristis) ; a 

 great plate of bone covered with grey skin, and set 

 along each side with a row of seiTied teeth. Here the 

 blades are similar in form, being long straight narrow 

 laminae of transparent chitine, set along each edge with 

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