HYDKOCAMPA NYMPHS ATA. 93 



thus the under -sides of the two pieces of leaf are turned 

 towards each other, though the edges of one are set 

 against the edges of the other ; there remains between 

 them a cavity for the dwelling of the larva ; and that 

 cavity would be more difficult to contrive if the upper 

 surface of one piece were applied to the under surface 

 of the other. 



" Sometimes the larva is content to attach the 

 piece to the under side of the leaf to which it has 

 brought it, . . . and that is at the time when it is 

 about to change to a pupa. Then it spins in the 

 cavity enclosed by the two portions of leaf a some- 

 what thin cocoon, but of very close tissue. 



" When the larva is not ready to change, it thinks 

 to make itself a case — a dwelling, which it can carry 

 about wheresoever it wishes to go. It begins by fixing 

 lightly — by tacking, so to say — the piece it has already 

 cut against the new leaf ; it leaves apparently all 

 round between the leaf and the piece at intervals, 

 but tolerably near one another, places by which it can 

 put out its head. But it is certain that the piece 

 which it has attached to the leaf serves as a model to 

 cut from it another piece of equal size and similar 

 shape. These two pieces together form its complete 

 covering ; the larva finishes uniting them all round 

 their outline, except at one of the ends, where the 

 two halves of the case remain simply resting against 

 one another. . . . 



" Whilst the larva continues to grow, its dwelling 

 is nothing but these two pieces of leaf fastened to- 

 gether, though when the time of its change draws 

 near, it carpets its case, making in it a cocoon of 

 white silk." 



As Reaumur speaks of finding cocoons under water 

 containing pupas, and as the pupse themselves are 

 furnished with spiracles similar to those of the larvae, 

 it might well be that ordinarily the pupation takes 

 place under water, but for the time the conduct of 

 my two larvas puzzled me, when I saw them making 



