50 THE METAMORPHOSIS. 



insects, whose larvae and pupae are inhabitants of the 

 water, respiring the air dissolved in that fluid by 

 means of branchial plates of various construction, and 

 are thus as completely aquatic in their nature as the 

 Crustacea, or even the still lower Annelidan worms. 

 The water-breathing aquatic larvae, however, usually 

 lose their gills on passing into the pupa state, and 

 even when the pupa retains these organs, the perfect 

 insect is always an air-breathing animal. The only 

 known instance of retention of the branchiae in the 

 mature state, is that presented by a North American 

 insect described by Mr. Newport. 



