96 hydrocAmpa nymph^eata. 



I now give the details of a case-making which I 

 watched throughout. The naked larva crawled to 

 near the tip of a leaf of Potamogeton natans, fixed its 

 anal legs near the side, and began to eat a little curved 

 channel from the edge through the leaf, working 

 from right to left, its head and body bending round 

 to the left more and more until three-fourths of the 

 intended cut had been accomplished ; then, still 

 keeping the same foothold, it ate back again from 

 left to right, clearing out and widening the channel ; 

 next it changed its foothold across the channel to the 

 fixed part of the leaf, whence, stretching out its head, 

 it continued eating from right to left, and so carried 

 on the curve of the channel quite up to the edge of 

 the leaf again, leaving only a very narrow isthmus 

 uncut ; then, as before, it ate backwards to widen the 

 last cut part of the channel; finally crossing over the 

 channel again, and taking its position on the now 

 almost detached piece, it ate away the last connecting 

 morsel at the very edge, and was adrift as upon a 

 raft. I noticed, however, that a change of plan took 

 place between the first and second parts of its work ; 

 the cut made from the first foothold on the side of the 

 leaf had a long oval curve ; when, however, crossing 

 the channel, the larva continued its work from its 

 foothold on the leaf, it did not go on from the very 

 end of the cut already made, but began again at a 

 point a little distance further back, thus finally 

 bringing out the channel with a shorter rounder 

 curve, which had the effect of making the detached 

 piece of leaf more symmetrical in outline. It was 

 now afloat, with its ventral and anal legs clinging to 

 its raft, but very soon it applied its thoracic legs to 

 the fixed part ot' the leaf, and, guiding its course by 

 them, conveyed itself and its raft under the leaf, 

 apparently looking for a suitable place whence to cut 

 the other half of its case ; presently it seemed to find 

 what was wanted, the floating piece was made fast, 

 and after some hours the upper half was cut out 



