298 Fresh Water Aquarium 



The Water Runner {Hydroiuctra lacustris) 

 lives in ponds and streams in the same lo- 

 calities in which the Gyrinus occurs. Like 

 these they play on the surface of the water, 

 but instead of swimming they run and slide 

 on the surface. Their legs are densely cov- 

 ered with fine hair and the air, gathered and 

 held by these hairs, gives them enough 

 buoyancy to prevent their body from sinking 

 into the water. Being perfectly harmless 

 they can be kept in every aquarium. 



May Fly or Caddis Fly (Phryganca gran- 

 dis decora), is a member of the nerve-winged 

 insects (Neuroptera), with four large mem- 

 branous wings of equal size. While the in- 

 sect itself has no value whatever for the 

 aquarium, its larvae form a very interesting 

 and desirable addition to the inmates. It is 

 known as the caddis, or case worm, a soft- 

 bodied, six-legged being, which, to protect 

 itself against its countless enemies, con- 

 structs a tube or baglike case, smooth on 

 the inside, but covered on the outside with 



