142 ORDER HEM I FT ERA 



and are attracted very much by lights. They constitute a 

 food supply for fishes and they themselves feed on other 

 aquatic organisms. One s})ecies in Mexico is dried and used 

 for food by the natives and is also sold in the markets as 

 bird food. There is some question as to their economic 

 importance. 



Notonectidse.^ — These are generally larger than the Corisidce. 

 The striking thing about them is that they swim back down- 

 ward, coming to the surface of the water at intervals for air. 

 Our common species is Notonecta undulata. This species 

 has a severe bite and it is best to handle it w4th care. 



Water Scorpions {Neyidoe). — The water scorpions are 

 characterized by a long respiratory tube at the end of the 

 body; a very much elongated coxa in the forelegs so that 

 the femur and tibia can be thrust out from the end of the 

 body to catch prey. They are generally found in shallow 

 water, secreted in dead leaves close to the bottom. How- 

 ever, they are strictly dependent on air for respiration and 

 get it by sticking this respiratory tube up to the surface of 

 the water. They are strictly carnivorous, puncturing their 

 prey and sucking the blood. If they are touched they feint 

 and their legs may be broken off without any motion on 

 their part. 



Belostomidse. — These are the giant water bugs and are the 

 largest bugs belonging to this order. They have a short 

 respiratory tube and a strong and somewhat curved beak; 

 and can inflict a very severe bite. They are quite preda- 

 ceous, feeding on young fish, and sometimes even those 

 larger than themselves. Thus they are of distinct impor- 

 tance as destroyers of fish. They go through all the stages 

 of their life-cycle below the surface of the water. The eggs 

 are laid under water on the stems of plants or in the case 

 of one species on the back of the insect itself. The eggs 

 are cemented so tightly that sometimes the shells remain 

 long after the eggs are hatched. The young at first are 

 nearly the form of the adults but without wings. They 

 grow by successive moults and with gradual appearance of 

 wing pads until they reach the adult stage. 



