ANATOMY AND PHYSIOLOGY 43 
ent; the hypopharynx is linear also and serves to conduct sa- 
liva; the labium forms a sheath, enclosing the other mouth 
parts when they are not in use; a pair of sensory lobes, termed 
labella, occur at the extremity of the labium. 
Fic. 
or 
Mouth parts of female mosquito, Culex pipiens. A, dorsal aspect; B, transverse 
section; C, extremity of maxilla; D, extremity of labrum-epipharynx; a, antenna; e, 
compound eye; i, hypopharynx; /, labrum-epipharynx; Ji, labium; m, mandible; mu, 
maxilla; », maxillary palpus.—B, after DIMMock. 
The cesophagus is dilated to form a bulb, or sucking organ, 
from which muscles pass outward to the skull; when these con- 
tract, the bulb dilates and can suck in fluids, as blood or water, 
which are forced back into the stomach by the elasticity of the 
bulb itself, according to Dimmock; the regurgitation of the 
food is prevented by a valve. 
The male mosquito rarely if ever sucks blood and its mouth 
parts differ from those of the female in that the mandibles are 
