122 HEMIPTERA. 



it under its wings, which is used for respiration, and 

 which also helps to lighten the body, so that it rises 

 quickly from the bottom of the pond whenever it 

 loosens its hold of an object to which it may be cling- 

 ing and allows itself to float upward. Notonecta is 

 obliged to come to the surface frequently, as the 

 greater part of the air being under the wings comes 

 in contact with the water but little. Corisa, another 

 genus of water-boatman, has its body almost com- 

 pletely enveloped with air, which ghstens like silver. 

 This air-film is constantly retained, and probably acts 

 as a tracheal gill, so that the insect is able to remain 

 under water a long time.^ 



BELOSTOMID.E. 



The giant water-bug, Belo stoma (Fig. 71), shows 

 several of the characteristic Hemipterous organs on 

 a large scale, and can be made very useful on this 

 account. The body is broad and flattened at the 

 edges. The head is remarkably small for such a large 

 insect, and the eyes take up a great part of it. At 

 first sight the antenn?e appear to be wanting, as they 

 are bent under and are entirely concealed by the eyes. 

 The position and unique structure of these organs 

 suggest some peculiarity in function, which can only 

 be ascertained with certainty by careful observations 

 of the habits of the animal. The sucking-tube is 

 short but strong, and with it the insect can inflict a 

 severe sting.- 



1 Comstock, American Nattii'alist, June, 1887, p. 577. 



2 Children will be interested in an article on " Plsh-Destroy- 

 ing Bugs" by Dimmock in The Sxuiss Cross for June, 1887. 



