INSECTS 



ular substance begins to harden, growth ceases, and the 

 external form of the insect will henceforth show no further 

 change in its structural features. 



The propupa of the moth remains for several days a 

 soft-skinned creature (Fig. 159 C) inside the cuticula of 

 the larva, during which time its body contracts in size and 

 its wings, legs, antennae, and maxillae lengthen. The wings 

 are flattened against the sides of the body, and the other 

 appendages are applied close to the under surface. Then 

 a gluelike substance is exuded from the body wall, which 

 fixes the members in their positions and soon dries into a 

 hard coating or glaze over the body and appendages, giving 

 to the whole a shell-like covering. In this way the soft 

 propupa (C) becomes a chrysalis (D). Finally, the old 

 caterpillar skin splits along the back of the first two body 

 segments, over the top of the head, and down the right side 

 of the facial triangle. The pupa now quickly wriggles out 

 of the enclosing skin and pushes the latter over the rear 

 extremity of its body into the end of the cocoon, where it 

 remains as a shriveled mass, the last evidence of the 

 caterpillar. 



The pupa, or chrysalis, of the tent caterpillar (Fig. 

 159 D) is much smaller than the propupa (C), and its 

 length is only about one-third that of the original cater- 

 pillar (A). The color of the chrysalis is at first bright 

 green on the fore parts, yellowish on the abdomen, and 

 usually more or less brown on the back. Soon, however, 

 the color darkens until the front parts and the wings are 

 purplish black, and the abdomen purplish brown. Though 

 the covering of the chrysalis is hard and rigid, the creature 

 is still capable of a very active wriggling of the abdomen, 

 for three of its intersegmental rings remain flexible. By 

 this provision the pupa is able to divest itself of the larval 

 skin. The pupae of some species of moths push them- 

 selves partly out of the cocoon just before the time of 

 transformation to the moth, and when the latter emerges 



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