54: THE BUTTERFLY, 



tween the chrysalis and the imago is far less than 

 that between the caterpillar and the chrysalis, the 

 wrinkled sheaths of the chrysalis confining parts 

 which differ in little more than size from the per- 

 fected organs of the imago. It is into the period 

 of quiescence at the close of the caterpillar state, 

 a period of only twenty-four to forty-eight hours, 

 that are crowded nearly all the really wonderful 

 alterations of structure in these insects, alterations 

 which affect not only the form 

 and relationship of the external 

 parts, but also those of all the in- 

 ternal organs. 



The head of the butterfly [Fig. 

 65] differs somewhat in general 

 form from that of the caterpillar, 

 the sides being greatly enlarged 

 and occupied by a pair of com- 



Fro. 65.-Side view 



ofheadofEpargyreud pound eyes of enormous extent, 



Tityrus, nat. size. 



supplanting the minute area oc- 

 cupied by the simple ocelli of the larva, or the 

 more extended and highly organized ocellar riband 

 of the pupa ; these eyes are convex hemispheres, 

 whose face is divided into innumerable hexagonal 

 facets scarcely more than one-hundredth of a 

 millimetre in diameter, arranged with great regu- 

 larity, each with its underlying structure of rod 

 and nerve, representing a single eye. 

 The immense development of the eyes has quite 



