INSECTS: THEIR MOUTHS 177 



simple cutting lancets, with a back and a keen blade, a 

 little widening at the tip. 



Besides these there is the tongue, consisting of a cen- 

 tral rod which is distinctly tubular, and of a thin blade 

 on each side, fine -edged and drawn to an acute point. And 

 also the labrum or upper lip, an organ having the same 

 general form, but constituting an imperfect tube; a tube, 

 that is to say, from which about a third of the periphery 

 is cut away, so as to serve as a sheath for the tongue, 

 which ordinarily lies within its concavity. 



I scarcely know whether this apparatus is not more 

 wonderfully delicate than any we have examined even 

 than that of the Flea. And how effective it is you doubt- 

 less well know; for when the array of lancets is introduced 

 into the flesh, you are aware that a tumor is left, which 

 by its smart, itching, and inflammation, causes much dis- 

 tress, and lasts many hours. This effect is probably pro- 

 duced partly by the deep penetration of the instruments 

 for they are fully one-sixth of an inch in length, and 

 they are inserted to their very base and partly by the 

 injection of a poisonous fluid, intended, as has been con- 

 jecturally suggested, to dilute the blood and make it more 

 readily flow up the capillary tubes. The channel through 

 which this fluid is injected is probably the tongue, which 

 you see to be permeated by a tube containing a fluid; and 

 the same channel may afford ingress to the diluted blood. 



The labium does not enter the wound. If you have 

 ever had the philosophic patience to watch a gnat while 

 puncturing your hand, you have observed that the knob 

 at the end of the proboscis is applied to the skin, and that 

 then the organ bends with an angle more and more acute, 

 until at length it forms a double line, being folded on 



