50 THE METAMORPHOSIS. 



insects^ whose larv^se and pupge 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 larvse, 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 branchige in the 

 mature state, is that presented by a North American 

 insect described by Mr. Newport. 



