HEMIPTERA. 1 8$ 



ing in the clypeus instead of being articulated to its tip. In the 

 males of Corisa the abdominal segments, especiall}' the four caudal 

 ones, are very unsymmctrical, being upon one side broken into 

 irregular-shaped fragments. 



These water-boatmen have the body flattened above, and swim 

 upon their ventral surface ; they differ in these respects from the 

 members of the next family. They swim with a quick, darting mo- 

 tion ; they use for this purpose chiefly their long, oar-like posterior 



. When in their favorite attitude, they are anchored to some 

 object near the bottom of the pond or aquarium by the tips of their 



g, slender, intermediate legs, at such times the fore legs hang 

 slightly folded, and the posterior legs are stretched out horizontally 

 at right angles to the length of the body. The body of these in- 

 sects with the air which clings to it is much lighter than water; 

 consequently, whenever they loose their hold upon the object to 

 which they have been clinging, they rise quickly to the surface, un- 

 they prevent it by swimming. They occasionally float on the 

 surface of the water, and can leap into the air from the water and 

 take Hight. 



The bodies of these insects, as they swim through the water, are 

 almost completely enveloped in air. The coating of air upon the 

 ventral surface and sides can be easily seen, for it glistens like silver. 

 - atching the insects carefully, when they are bending their bod- 

 an be seen to fill the spaces between the head and protlmrax. 

 and between the prothorax and mesothorax. The space ben< 

 the wings is also filled with air. When these insects are in impure 

 water, they must come to the surface at intervals to change this sup- 

 ply of air. Hut I have demon that in good water it is not 

 v for them to do this. The air with \\hich the body is 

 clothed is purified by contact with the fine particles of air n 

 through the water; so that the insect can breathe its coat 

 and again indefinitely.* 



:><>atmen arc carnivorous, feeding upon other in 



o aquatic plants ; and the yomi uiul 



in the same situations as the adults. 



" In Mexico, the eggs ot said to be 



from water-plants, and nsl as an article of food by the d \wllers 



r the la) md. The natives cultivate a sedge 



upon which I Otit tlxireggs. This sedge is made 



* See acr , experiments in A> 



