INSECTS : THEIE MOUTHS. 149 



drical joints, which are beset on all sides with short arched 

 hairs, but have besides a whorl of radiating long hairs 

 surrounding the bottom of each joint. • The effect of this 

 is exceedingly light and elegant. 



Between these projects a long cylinder, which represents 

 the lower lip (labium) ; it slightly swells towards the tip, 

 where it forms a round, nut-like knob, covered with 

 exceedingly minute papillae, and no doubt constituting a 

 highly sensitive organ of touch. For the greatest part of 

 its length it is covered with lined scales, and with short 

 arched hairs like the antennas, while each side of its base 

 is guarded by a labial palp of three joints. 



On applying a graduated pressure, slowly increased to 

 actual contact of the plates (or as near an approximation 

 to it as we can effect), we see first that the nut-like tip of 

 the labium expands into two concave leaves, like the bracts 

 of a bud, and displays two pairs of more delicate leaves 

 within them. Then from a groove along the upper side 

 of the labium spring out several filaments of great elas- 

 ticity, and of the most delicate tenuity. One pair of these 

 represent the mandibles ; they consist each of a very nar- 

 row blade, with a stronger back like that of a scythe. 

 Their tip is brought to a most acute point, and the edge 

 in immediate proximity to this is cut into about nine teeth, 

 pointing backward ; the rest of the edge is smooth, but 

 the whole blade is crossed by a multitude of oblique lines 

 of great delicacy, which may be intended to keep the edge 

 constantly keen. 



Next come the maxilla, or lower jaws, horny filaments 

 as long as the former, but still more delicate, constituting 

 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 

 central 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 



