THE CATERPILLAR AND THE MOTH 



prepupal stage of the larva. The insect in the prepupal 

 stage has suffered no change in external structure, it still 

 wears the larval skin, and its visible difference from the 

 active larva is a mere alteration in form. Internally, how- 

 ever, important reconstructive processes are now taking 

 place. 



The internal activities of reconstruction, which bring 

 about the pupal metamorphosis of the larva to the adult, 

 begin at the head end of the insect and progress poste- 

 riorly. They are preceded by a loosening and subsequent 

 detachment of the larval cuticula from the cellular layer 

 of the skin, or epidermis, beneath it. The latter, known 

 also as the hvpodermis, freed now from restraint, enters a 

 period of rapid growth. On the head, the head walls are 

 remodeled and take on a new form, and new antennae and 

 new mouth parts are produced. The new structures have 

 no regard for the forms of the old, though each is pro- 

 duced from a part of the corresponding larval organ. The 

 new antennae, for example, are formed from the larval 

 antennae, but the antennae of the moth are to be much 

 larger than those of the caterpillar. Only the tip, there- 

 fore, of each new organ can be formed within the cuticular 

 sheath of the old; the base pushes inward, and the elon- 

 gating shaft folds against the face of the newly forming 

 head. The same thing is true of the maxillae and labium, 

 but in the case of the mandibles the procedure is simpler, 

 for the jaws are to be reduced in the moth. The epi- 

 dermal core of each mandible, therefore, simply shrinks 

 within the cuticular sheath of the larval organ, leaving 

 the cavity of the latter almost empty. 



As the separation of the cuticula from the epidermis 

 progresses over the region of the thorax and a free space 

 is created between the two layers, the wing buds, which 

 heretofore have been turned inside the caterpillar's body, 

 now evert and come to be external appendages of the pupal 

 body though still covered by the cuticula of the larva 

 (Fig. 159 C, fVi, fV 3 ). The legs of the moth pupa are 



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