ANATOMY AND PHYSIOLOGY 37 
insects is a simple plate, hinged to the clypeus and moving up 
and down, though capable of protrusion and retraction to some 
extent. It covers the mandibles in front and pulls food back 
to these organs. On the roof of the pharynx, under the la- 
Fic. 44. 
Mouth parts of a cockroach, Ischnoptera pennsylvanica. A, labrum; B, mandible; 
C, hypopharynx; D, maxilla; E, labium; c, cardo; g (of maxilla), galea; g (of labium), 
glossa; /, lacinia; /p, labial palpus; m, mentum; mp, maxillary palpus; p, paraglossa; 
pf, palpifer; pg, palpiger; s, stipes; sm, submentum. B, D and E are in ventral 
aspect. 
brum and clypeus, is the epipharynx; this consists of teeth, 
tubercles or bristles, which serve in some insects merely to 
hold food, though as a rule the epipharynx in mandibulate 
insects bears end-organs of taste (Packard). 
The mandibles, or jaws proper, move in a transverse plane, 
being closed by a pair of strong adductor muscles and opened 
by a pair of weaker abductors. The mandible is almost 
always a single solid piece. In herbivorous insects (Fig. 
45, 4) it is compact, bluntly toothed, and often bears a molar, 
or crushing, surface behind the incisive teeth. In carnivorous 
