2 LI [February, 



He watched some of the larger larvse malcuig cases, and thus describes wliat he 

 saw: — "To make itself a new case, the larva clings to the lower side of a leaf of 

 " Potamofjeton ; with its 'teeth' it pierces some portion of the leaf, and then it 

 "bites it by degrees in following the curved line, which must have the outline of the 

 " piece it wishes to detach. . . . Wlien the larva has cut, like a piece of cloth, 

 " a bit of the leaf of suitable size and figure, it has half the stuff necessary for 

 " making itself a case ; it seizes this piece with its ' teeth,' and carries it either under 

 "another part of the same leaf, or beneath another leaf; it stops and fixes it in the 

 " place which seems suitable. But it is to be noticed that it places it so that the 

 " under-side of the piece is turned towards the under-side of the new leaf, in order 

 " that the interior sides of the case are always made of the under surface of the two 

 " pieces of leaf. And the caterpillar has determined to use them thus for a good 

 " reason : although the leaves of Potamogeton are tolerably flat, they are a little 

 " concaye below ; thus the under-side 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 tliem a cavity for the dwelling of the larva ; and that cavity 

 " would be more difBeult 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 



" loaf, 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 somewhat 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 cai-ry 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 aud 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 whicli 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 together, 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 pupa?, and as 

 the pupa; Lhemselves are furnished with spiracles similar to those of the larva;, it 

 might well be that ordinarily the pupation takes place under water, but for the 

 time the conduct of my two larva; puzzled me, when I saw them making their cocoons 

 above the surface ; perhaps there was not a suflicient quantity of Potamogeton left to 

 satisfy their requirements in spinning themselves up. Reaumur notices — but 

 confesses he cannot explain — the fact that the cases, though constructed entirely 

 under water, are yet themselves quitJ dry and free from water — diving bells in fact — 

 and he credits the larva with some power of expelling the water after it has completed 

 a case : his description of colour of the larva seems to refer to its appearance under 

 water, when it shows luminous with a brilliant silvery glitter as it advances the front 

 segments out beyond its case, for he says " almost all its body is white, and of a 

 white that must be (called) glittering," thougli»lie calls the head brown and the back 

 of the first two or three tii-'ments tinted with brown. 



