6 
^8 
1. The labium, forming the sheath. 
2. The labrum and epipharynx \ 
or upper lip ! forming 
3. The hypopharynx, or tongue the 
4. Two mandibles i stylets. 
5. Two maxillae I 
6. Two maxillary palps. 
Fig. 51. Fhe 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 Lahella .—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 
