io6 The Under-Water World 



they have at one end seven short fila- 

 ments that are supposed to function 

 respiratorily . Ranatra's eggs possess 

 only two of these filaments and are laid 

 on the plants. 



Coming now to the second class that 

 is, the insects that are aquatic only 

 during the earlier stages we find many 

 very interesting forms. There are, for 

 instance, the May-flies the insects of a 

 day. They are, as is well known, eagerly 

 devoured by fishes, and the artificial flies 

 known as " duns/' r< spinners, " drakes/' 

 etc., used by fishermen are supposed to 

 be copies of certain May-flies. The 

 larvae live in ponds, lakes and streams, 

 both fast-running and slow. They vary 

 in detail but are all more or less alike 

 in general form, possessing tracheal gills 

 arranged along the sides of the body. 

 The eggs are sometimes dropped or 

 deposited on the surface of the water or 

 are concealed beneath stones at the 



