92 HYDR0CA.MPA NYMPHS ATA. 



Mr. McLachlan has most kindly given me the oppor- 

 tunity of reading Reaumur's wonderfully interesting 

 ' Memoire des Chenilles Aquatiques,' by far the greater 

 portion of which refers to Hydrocamjpa nymphasata ; 

 and I should like to quote his observations on a 

 few points which I had not myself the opportunity 

 of observing. 



Reaumur found, near the edges of the Potamogeton 

 leaves, many little clusters of the eggs, and he seems 

 to think that the moth covers them with bits of the 

 leaves ; but as he never closely watched a moth laying 

 her eggs (and it is hard to understand how she could 

 effect the concealment in the way he supposes), he 

 cannot say how she managed to cover them. 



As soon as ever the larvse are hatched — at the end 

 of July or the beginning of August — he says each 

 makes a little case for itself, and as it grows, con- 

 tinually makes fresh cases adapted to its increasing 

 size. 



He watched some of the larger larva3 making cases, 

 and thus describes what he saw : — " To make itself a 

 new case, the larva clings to the lower side of a leaf 

 of Potamogeton ; 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. . . . When the 

 larva has cut, like a piece of clpth, 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 Potamo- 

 geton are tolerably flat, they are a little concave below ; 



