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its case for pupating, it joins the two pieces so closely together, as to 

 render it watertight, but before that time the openings at the ends are 

 generally so wide that the water cannot be kept out. I am, however, 

 disposed to agree with Reaumur's statement that the larva can control 

 the admission of water to its case, and probably this is regulated by 

 its requirements in the matter of respiration, and must be managed 

 by enlarging or contracting the orifice at either end. 



When a larva makes use of Myosotis, after selecting the end of a 

 leaf, and detaching a piece of proper length by a semicircular cut, it 

 floats off upon it towards the end of another leaf ; there it either 

 mounts on the upper surface, and turns over the piece it is carrying 

 so as to form its new roof, or else carries it underneath and fastens it 

 there as its new floor ; either way, after fastening the edges of the 

 detached piece in place, the larva seems to be at leisure in cutting out 

 what is needed from the leaf to complete its case, eating away the 

 surroundings, and not merely making a cut ; the cavity between the 

 roof and the floor seems formed by having one of them broader in the 

 first instance than the other, so that when the edges are joiaed, there 

 is necessarily a bulging out of the broader piece. 



"When Sparganium is the material, the case is of a narrower and 

 more elongated form, the floor being the flatter side, and thus shorter 

 than the roof, which is arranged so that the keeled surface of the 

 leaf is outside, and the thin side-edges drawn inwards, and thus made 

 to help in the formation of the cavity. Not unfrequently the case is 

 formed of two sorts of leaf, for a larva is not particular to have its 

 case all of the same material ; apparently in its growth between two 

 moults it changes only one-half of its case at a time, whereas after a 

 moult it sometimes makes a new case entirely ; when, therefore, it 

 wants only a new roof or a new floor, it takes it from a suitable 

 plant nearest at hand, cutting the new piece a little larger than its 

 predecessor, and in this way, by changing the top and bottom 

 alternately, it soon brings a small case up to a good size. 



On June 11th, I noticed a larva looking as if about to moult, and 

 isolated it for observation: the moult took place on 13th; after the 

 skin burst at the neck, the old head-cover first fell off, and then the 

 (almost colourless) larva began slowly to advance into the water out 

 of its case until nearly exposed, then it stopped still for about ten 

 minutes, when suddenly the hinder segments were set free with an 

 effort that sent the case adrift, while the larva remained quite naked 

 in the water : I secured the abandoned case, and opening it found the 

 cast flaccid skin — not shrivelled up — but held out at full length by 

 silk threads along the ventral region. 



