356 NATURAL HISTORY OF AQUATIC INSECTS ch. 



aquatic Rhynchota thc)' fly vcr}- well. Corixa flies 

 at night, and has been seen to fl}- into an open 

 window in August, being attracted by a light. Thc 

 head in both genera is transversely elongate, the eyes 

 large, and the antenucne concealed, as in Nepidai. 

 The mouth, as in other Rhynchota, is suctorial, and 

 armed with a stout proboscis, rather long in Noto- 

 necta, short in Corixa. The proboscis is piercing, and 



Fig. 109.— Rostrum and setae (mandible and toothed maxilla) of Notonecta glauca. 



capable of inflicting a slight wound on the hand of 

 anyone who seizes the Insect. The bod}- is velvety 

 and overspread with a glistening air-film, which is 

 conspicuous on the under-side, but elsewhere hidden 

 by thc wings. Notonecta is inflated by air to such 

 an extent that it is very buoyant ; it has to cling to 

 weeds or other fixed objects when it wishes to remain 

 below, and as soon as it relaxes its hold it rises to 

 the surface. This uncommon buoyancy is probably 



