HEMIPTERA 371 



Twenty species of water-striders have been found in America 

 north of Mexico; these represent seven genera. These genera are 

 separated by Hungerford ('19) as follows: 



A. Inner margin of the eyes sinuate behind the middle. Body comparatively 

 long and narrow; abdomen long. (Subfamily Gerrinae). 

 B. Pronotum sericeous, dull; antennae comparatively short and stout. 



C. First segment of the antennae shorter than the second and third taken 

 together. 

 D. Antennae half as long as the body; sixth abdominal segment of the 



male roundly emarginate Limnoporus 



DD. Antennas not half as long as the body, not extending beyond the 

 thorax; sixth abdominal segment of the male doubly emarginate. 



Gerris 



CO. First segment of the antennae longer than the second and third taken 



together Gerris 



BB. Pronotum glabrous, shining; antennae long and slender. . .Tenagogonus 

 AA. Inner margin of the eyes convexly rounded. Body comparatively short 

 and broad ; abdomen so short as to appear almost nymphal in some forms. 

 (Subfamily Halobatinae) . 

 B. First antennal segment much shorter than the other three taken together; 

 not much longer than the second and third taken together, and some- 

 times shorter. 

 C. Fourth (apical) segment of the antennae longer than the third. 

 D. Eyes fairly prominent ; colors of body black and yellow. .Trepobates 

 DD. Eyes smaller, widely separated; body lead-colored, sericeous. 



ocean dwellers Halobates 



CC. Fourth segment of antennae never more than equal to the third; 

 basal segm.ent of anterior tarsi much shorter than the second; 

 hind femur equal to or much shorter than the hind tibia and tarsus 



taken together Rheumatobates 



BB. First antennal segment nearly equal to the remaining three taken to- 

 gether, much longer than the second and third; antennae almost as 

 long as the entire body; hind femur twice as long as hind tibia. 

 Metrobates 



Gerris. — Of the twenty species of water-striders found in this 

 country, nine belong to this genus ; a common species in the East is 

 Gerris conformis (Fig. 426). 



Fig. 426. — Gerris conformis. 



Limnoporus. — ^We have only a single species of this genus, L. ru- 

 foscuiilldtus. 



Tenagogonus. — Three species are listed from our fauna, only one 

 of which has been found in the North; this is T. gillettei, which is 

 reported from Ohio. The others are found in Florida and California. 



Metrobates. — Our only species, M. hesperius, is foimd in Ontario 

 and the eastern part of the United States. 



