POND LIFE. 123 



method of respiration, the ways of locomotion, and 

 the nature of their food. Offer them both living and 

 dead insects, snails, and meat. Preserve one or more 

 larvas in alcohol, and put them witn the adults in your 

 collection. 



The Back-swimmers {School PFor/&).— When the 

 different kinds of insects that you have collected by 

 sweeping submerged plants have been placed in 

 aquaria, you will be able to recognize the back-swim- 

 mers by the fact that they swim up- 

 side down. One of these insects is 

 represented back uppermost by Fig. 



lOI. 



The back-swimmers love to float '°' '°^' 



at the surface of the water". Here they hang motion- 

 less, back downward in a slanting position, with the 

 tip of the abdomen at the surface, and the head con- 

 siderably submerged. When in this position the 

 fore and middle legs are slightly bent, so that the 

 claws are at the surface, as if the insect were clinging 

 to the ceiling of its room ; while the longer, oar-like 

 hind legs are nearly straight, and project down into 

 the water somewhat; here they are held in the posi- 

 tion of the beginning of a stroke, as if the creature 

 were waiting for the word go ; and they can go quick- 

 ly and rapidly like an expert sculler. Often they 

 will swim to the bottom of the pond, where, clinging 

 to a stone or plant, they will rest quietly, apparently 

 as much at home as when at the surface. 



In their journeys from one part of the aquarium 

 to another, they are forced to keep their oars in con- 

 stant motion. For these topsy-turvy creatures carry 

 a load which is so light that the moment they stop 



