FIELD WORK ON HEMIPTERA. 99 



side-wheeler alongside a big, steady, ocean-going steamer, 

 are the back swimmers, performing such feats as you and 

 I would have reason to be proud of, if we could do them, 

 always swimming back downward, the hind legs directed 

 forward, and so formed as to serve as oars. These are 

 blue-gray and white insects, and they lash the water 

 smartly as they dart here and there in search of food. If 

 you can capture one, put it into your pail, which should 

 be at least half full of the pond water; and you will see, 

 especially if you have brought along the reading glass, that 

 the rear end of the body of each of these back swimmers 

 is tilted slightly upward, so that the wing margins are 

 slightly above the water line. The back swimmers are air- 

 breathing insects, and they store their air supply between 

 the abdomen and the wing-covers. 



If you stoop on your hands and knees, or lie down so 

 that you can look into the depths of the pond and do it 

 quietly there may be found other insects clinging to the 

 grass stems or other objects under the water; these may 

 at first sight look very much like the back swimmers, but 

 these insects prefer to stay below the water surface, while 

 the back swimmers come below only when something dis- 

 turbs them above. The grass stems may be swept with 

 your dip net for some of these insects, and when you have 

 one of them in hand, if it has the characteristic beak, it is 

 presumably a water boatman. This new insect should 

 be flat on the back, instead of keel-shaped as the back 

 swimmers are. You may also find, crawling about over 

 the pond mud, a big brown insect about two inches or 

 more long. Its two front legs are held elbowed, seeking 

 what they may grasp. Send down your dip net or the 

 dipper and get one of these insects; and when you have 

 him look for the long beak "laid away" between the front 



