HOW TO KNOW THE IMMATURE INSECTS 



7b. Body not toad-shaped; fore legs simUar to middle legs. 



FomUy OCHTERIDAE 



These are shore-inhabiting bugs. The family includes only a single 

 genus, Ochterus and only three species have been described in the 

 United States. They are all predacious. 



8a. Head as long as entire thorax. Fig. 361. Family HYDROMETRIDAE 



The members of this family are called 

 water-measurers because they creep slowly 

 upon the water surface. The body is very 

 slender and the head is as long as the en- 

 tire thorax. Only three species have been 

 described in the United States. 



Fig. 361. Hydrometra 

 martini Kirk, 4th in- 

 star. 



8b. Head shorter than thorax 9 



9a. Beak 4-segmented; hind femur extending much beyond the apex 

 of abdomen. Fig. 382 Family GERRIDAE 



Fig. 362. Gerris remigis 



Say, 1st instar. 



The water-striders skim rapidly over 

 the water surface and often congregate in 

 large numbers. They are predacious and 

 feed upon insects that fall into the water 

 or they sometimes jump to capture their 

 preys. Only about 20 species have been 

 described in the United States as belong- 

 ing to the genus Geriis. A few live on salt 

 water and are truly marine. 



131 



