SPHINX CHERSIS 155 



The rest of tlie process until the pupa was free occu- 

 l>ied thirty-one minutes. 



The skin grew more wrinkled on the anal end, and 

 stretched taut over the abdominal segments, while the 

 lower part of the body began to contract and expand 

 in such wise as to move up toward the third segment, 

 and with such force that the skin split before and 

 between the brown dashes on that segment, then 

 l^arted as far as the head. At this point the creature 

 turned over on its back. 



The third segment was pushed out first, then the 

 second, then the mask was split, and the first segment 

 came out, while the head was loosened from the old skin, 

 and first the antennsB, then the tongue-case, then the 

 legs appeared separate and free from the body ; but as 

 the head was pulled out they fell into place on the 

 thorax, and lay close to it and to each other. This 

 explains the position of the caterpillar's head in the 

 beginning. The appendages must lie flat on the 

 thorax for safety and compactness, and the drawing 

 backward of the head in freeing itself from the larva- 

 skin causes them to fall into their places. It is one of 

 the most beautiful processes of adaptation we have 

 ever seen, although it fails now and then, when the 

 pupa either dies or gives an imperfect moth. 



The rest of the pupation was very rapid. The seg- 

 ments in the larva-skin contracted while those without 

 expanded, thus pushing the skin down. Each seg- 

 ment, as it emerged, expanded in its turn, and the push- 

 ing was almost continuous until the skin dropped off 

 the anal end of the soft, green, shapeless — or nearly 

 so — pupa. 



