ioo The Under-Water World 



in which her eggs are deposited and kept 

 free from harm until the larvae hatch. 

 This cocoon is usually attached to the 

 floating leaf of some pond weed and has 

 at one end a neck protruding above the 

 surface, admitting air to the interior. 

 The case, which may well be called a 

 cradle, is quite waterproof. The young 

 larvae, on hatching, make their way out 

 through the bottom. The adult beetle, 

 unlike Dytiscus, is usually herbivorous, 

 only turning its attention to a meat diet 

 during the breeding season : the larvae, 

 however, prey upon various forms of 

 pond life. When about to pupate the 

 larva forms a cell in the soil of the pond 

 side and there undergoes the wonderful 

 transformation. Hydrophilus is not 

 nearly such a strong swimmer as Dy- 

 tiscus, for the legs work alternately and 

 are not so well adapted for swimming. 

 Once common in this country, this 

 species is now somewhat rare ; but on 



