30 



ZOOLOGY 



Some of tlic hinder rings l:iear short, stubby feet. This is the 

 lar^•al stage of the Ijutterfly, and is commonl}' known as the 

 caterpillar (Fig. 31). 



The caterpillar feeds ravenously and grows rapidly. Its 

 hody is enclosed in the cuticiila. As the caterpillar grows, 

 this skin is put under tension until finally it bursts at the 



Fig 



-Molting caterpillar. 



Fig. 3.3 



-Period of stretching; old 

 cuticula to left. 



anterior end (Fig. 32), and the caterpillar emerges, provided 

 with a new ctiticula formed beneath the old one. This new 

 cuticula is, at first, elastic, and the caterpillar takes advantage 

 of this fact to increase its length and diameter by as much 

 as one-third (Fig. 33). The new skin rapidly hardens, and so 

 confines the ever-developing caterpillar until it is again unal;)le 

 to 'i\itlistand the internal pressures. Then another molt 

 occurs. Thus the cuticula of the caterpillar makes it neces- 

 sarj' that growth should not be continuous, but should proceed 



