130 THE STUDY OF INSECTS. 



Family Notonectid^e (No-to-nec'ti-dae). 

 The Back-swimmers. 



The Back-swimmers have the back shaped like the 

 bottom of a boat, instead of flat like the true water-boatmen 

 and they differ from all other aquatic bugs in that they 

 always swim on their backs. 



The favorite attitude of the Back-swimmers is floating on 

 the surface of the water, back downward, with the hind end 

 of the body projecting sufficiently to admit of air being 

 drawn into the space beneath the wings. When in this 

 position their long oar-like hind legs are stretched outward 

 and forward, ready for action. When disturbed they dart 

 away toward the bottom of the pond, carrying a supply of 

 air beneath their wings. Occasionally these insects will 

 float on the surface of the water with their backs uppermost; 

 and, like the water-boatmen, they can leap into the air from 

 the water and take flight. 



The Back-swimmers feed upon insects and other small 

 animals. In collecting them care must be 

 taken or they will inflict painful stings with 

 their sharp and powerful beaks. 



The greater number of our common spe- 



YiG.itg—Notonecta . ; ° m 



unduiata. c { es G f this family belong to the genus Noto- 



necta (No-to-nec'ta) (Fig. 149). 



Family NEPID.E (Nep'i-dae). 



The Water-scorpions. 



The Water-scorpions have two long bristles on the end 

 of the body, which are grooved on the inner side. By put- 

 ting these bristles together a long tube is formed, which the 

 insects can project to the surface of the water, and thus ob- 

 tain air for breathing, while resting on the bottom of the 



