ENSECTA; CONTINUED 



209 



The larva of the lepidoptera is often very harmful as it feeds 

 on man's crops, the multitude of so-called " worms " being only 

 too familiar examples. The pupa stage of the silk moth furnishes 

 us with silk from the threads of its cocoon. The adults aid in 



Courtesy of the A merican Museum of Natural History. 



FIG. 68. This caterpillar of the monarch butterfly is ready for the meta- 

 morphosis. It hatched in late summer and grew for two weeks. It stopped 

 eating, chose a secure spot and spun a small thick carpet of silk. It walked over 

 this until the hind feet were entangled in the silk, then it hung head downward, 

 motionless. The skin now loosens, and after twenty-four hours splits over the 

 head. At this stage the caterpillar, by musuclar contraction works the skin 

 off upward into a small shriveled mass; then during the few seconds longer 

 that it still remains attached to the skin, it reaches out its slender end and with 

 great effort and force pushes it up into the silk carpet. The whole process has 

 taken but three or four minutes. Slowly the shape changes, the segments above 

 contracting, the form rounding out; and behold an emerald-green chrysalis 

 studded with golden spots! In two weeks the pattern of brown and orange 

 wings begins to show through, finally the chrysalis skin splits over the head, 

 and the butterfly crawls out. 



