i66 



in the lower lip or labium. The proboscis con- 

 sists of (Fig. 43) : — 



1. The labium, forming the sheath. 



2. The labrum and epipharynx, "j 



or upper lip | forming 



3. The hypopharynx, or tongue j> the 



4. Two mandibles j stylets. 

 5., Two maxillae j 



6. Two maxillary palps. 



W7" 



Fig. 43. The Proboscis (Labium and Stylets), after Ndttall 



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. 43). 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. 



