March, 1913.] Barber: Aquatic Hemiptera. 31 



forms prefer the current of swiftly moving streams, but the majority- 

 find more congenial surroundings on the surface of quieter waters 

 and a few may even make excursions upon land, where they may be 

 found in damp situations. They are all carnivorous, using the fore 

 legs for holding their prey, which usually consists of dead or living 

 insects. They all hibernate, concealing themselves at the bottom of 

 their retreat to reappear again on the surface early in the spring. 



The forms which walk about on submerged sticks or stem of plants 

 beneath the water belong to the family Nepidae. The most striking 

 modification they present is a long respiratory tube through which 

 they may breathe surface air while the body is concealed beneath the 

 water. Their legs are long and slender and the fore legs are strong 

 and raptatorial for holding the prey. They more frequently occur 

 in shallow, sluggish streams or ponds well supplied with plant life. 

 Only three species are likely to occur in this vicinity belonging to the 

 genus Nepa and Ranatra. 



The free swimming forms are more abundant, locally, than in the 

 two preceding groups. They usually have the hind pair of legs either 

 broadened or fringed with long hairs to resist the water and serve as a 

 swimming organ. Here are included the families Corixidee, Belo- 

 stomatidae, Naucoridae and Notonectidse — a group of carnivorous 

 forms, with the possible exception of Plea striola, having the custom- 

 ary short, stout beak. Some of these species are of economic impor- 

 tance as they frequently attack young fish or destroy their eggs. 



The Corixidae, or water boatmen, are the most numerous in species 

 The hind legs are fringed with long hairs and their fore legs are pe- 

 culiarly modified, bearing characters which are largely used in their 

 specific differentiation. Carrying a supply of air beneath the elytra, 

 they may remain submerged for an indefinite period. 



The Belostomatidje include some of the largest hemiptera known. 

 The second and third pairs of legs are broad and paddle like and 

 fringed with long hairs. The fore legs are developed into strong 

 clasping organs. They are good swimmers and strong fliers, fre- 

 quently attracted to light several miles from their breeding places. 



The Notonectidae, or back swimmers, have the not much broadened 

 swimming hind tibiae fringed with hair and the modified clasping fore- 

 legs. The ventral surface is provided with a mass of long hairs which 

 enmeshes a supply of air for use beneath the surface. The species 



