INSECTS 



the species as a whole. Independence entails responsibil- 

 ities. A creature that leaves the beaten paths of its an- 

 cestors must learn to take care of itself in a new way. And 



Fig. 152. The head of a tent caterpillar 



A, facial view. B, under surface. C, side view. Ant, antenna; Clp, clypeus; 



For, opening of back of head into body; Hphy, hypopharynx; Lb, labium; Lm> 



labrum; Md, mandible; Mx, maxilla; 0, eyes; Spt, spinneret 



this the caterpillar has 

 as it has come up the 1 

 possesses both instincts 



Fig. 153. The mandibles, or 

 biting jaws, of the tent cater- 

 pillar detached from the head 

 A, front view of right mandi- 

 ble. B, under side of the left 

 mandible, a and p, the an- 

 terior socket and posterior 

 knob by which the jaw is 

 hinged to the head; EMcl, 

 RMcI, abductor and adductor 

 muscles that move the jaw in 

 a transverse plane 



learned to do preeminently well, 

 ong road of evolution, till now it 

 and physical organs that make it 

 one of the dominant forms of in- 

 sect life. 



The external organs of princi- 

 pal interest in the caterpillar are 

 those of the head (Fig. 152). 

 These include the eyes, the an- 

 tennae, the mouth, the jaws, and 

 the silk-spinning instrument. A 

 facial view ot a caterpillar's head 

 shows two large, hemispherical 

 lateral areas separated by a medi- 

 an suture above and a triangular 

 plate (Clp) below. The walls of 

 the lateral hemispheres give at- 

 tachment to the muscles that 

 move the jaws, and their size is 

 no index of the brain-power of 



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