I. 



2. 



3- 

 4- 



6. 



138 



The labium, forming the sheath. /; 



The labrum and epipharynx j 



or upper lip j forming 



The hypopharynx, or tongue ) the 



Two mandibles [ stylets. 

 Two maxillae 

 Two maxillary palps. 



Fig. 51. The Proboscis (Labium and Stylets), after Nuttall and 



Shipley. Right hand, cross section of Proboscis. The Palpi 



are not shown 



The Labium. The labium forms the thick and 

 scaly proboscis as usually seen. On its dorsal surface 

 it is hollowed out, and in this hollow run, as in a sheath, 

 the piercing mouth parts or stylets (Fig. 51). The 

 labium itself does not penetrate the skin, but becomes 

 sharply bent during the act of biting, just as when a 

 cane walking stick is pushed against the ground. This 

 may easily be seen if a mosquito is watched during the 

 process of biting. 



The Lobelia. Attached to the end of the labium 

 by a hinge joint on either side are two leaf-like processes, 

 the labella (Fig. 51). It is through the angle made by 

 the two labella that the stylets pass, as a billiard cue 



