HEMIPTERA 373 



Hebrus. — In this genus the antennas consist of five segments, not 

 counting a minute segment at the base of the third. The 

 adults are always winged. Four species occur in our fauna. These 

 bugs are found on moist earth at the margins of pools and run out 

 upon the water when disturbed; they are also found on floating 

 vegetation. 



Merragdta. — In this genus the antennas are four-jointed not count- 

 ing the small segment at the base of the third. The adults are dimor- 

 phic, short-winged and long-winged forms occcurring in the same 

 species. These insects inhabit still and stagnant waters and often 

 descend beneath the surface; at such times the body is surrounded 

 by a film of air. Only two species have been found, as yet, in this 

 country. 



Family HYDROMETRID^ 



The Water-Measurers 



The members of this family are very slender insects, with linear 

 legs andantennee (Fig. 428). The head is as long as the entire thorax, 

 although this region is long also. The eyes are 

 round, projecting, and placed a little nearer the 

 base than the tip of the head. Ocelli are absent. 

 The antennas are four-jointed; the beak is three- 

 jointed; and the tarsi are three-jointed. 



These insects creep slowly upon the surface of 

 the water; they carr>' the body considerably ele- 

 vated, and are found mostly where plants are 

 growing in quiet waters. It was probably their 

 deliberate gait when walking on water that sug- 

 gested the generic name Hydrometra, or water- 

 measurer. In this country these insects have 

 been commonly known under the generic name 

 Limnobaies, or marsh-treaders ; but Hydrometra 

 is much the older name. 



Only three species have been found in the 

 United States. One of these, Hydrometra martini Fig. 428.— Hydrome- 

 (Fig. 428), is widely distributed. The other two, ''« marfini. 

 Hydrometra anstralis and Hydrometra wileyi, are 

 found in the South. These insects are dimorphic both winged and 

 wingless forms occurring in the same species. Descriptions of the 

 three species are given by Hungerford ('23). 



The egg of Hydrometra martini is remarkable in form; it is figured 

 on page 167. 



Family SCHIZOPTERID^ 



The Schizopterids 



This family and the following one, the Dipsocoridce, constitute a 

 quite distinct superfamily, the members of which are most easily rec- 



