362 Annals Entomological Society of America [Vol. IX, 



on their prey from ambush, seizing it in their strong front claws 

 and deadening it by injecting their narcotic saliva. They 

 catch fish and in some parts of the world are known as fish- 

 killers. The food of the Corixidce is scarcely known, although 

 Abbott surmises that Rhamphocorixa acuminata feeds on an 

 Ostracod, which might lead to the conclusion that this family 

 is no exception to the general rule in aquatic Hemiptera. 

 It may also be presumed that they are herbivorous, as they are 

 not fitted with the means to seize living things. 



The next to engage our attention are the Gymnocerata 

 Littoralia, the surface-dwellers, the water-striders, so-called, 

 comprising the GerridcE and allied families. Here, as might 

 be expected, the environment is more uniform and we therefore 

 find the adaptations less in number and not so unique in 

 character as in the Cryptocerata. The antennae are free, the 

 legs are little changed in the majority, the food is animal, 

 respiration is uncomplicated, and in general the entire structure 

 is simpler. 



The universal and most striking adaptation to life upon the 

 waters is the greater or less thickness of the velvety pile that 

 covers the bugs. The object of this is to prevent the insect 

 from getting wet, by enmeshing a film of air which will repel 

 water from its body. On the under side of the body, the pile 

 is more or less silvery in color, while the upper side partakes of 

 the general hue of the species. All the forms — fluviatile, 

 lacustrine, oceanic — have this peculiarity in varying degree. 



It is said that some species when closely pursued dive to 

 escape. This submergence has actually been seen in Rhagovelia, 

 but not for the purpose of escape. This form, when under 

 water, is covered with a silvery coating of air. Although 

 Gerris is said thus to evade pursuit, I have never seen any 

 of our native species try this in spite of all manner of effort 

 and constant attack with a net. At any rate, Rhagovelia, 

 in my observation, drowns in a short time and Gerris does not 

 long survive submergence. 



The only other adaptation is in the structure and function 

 of the legs. In general, in Gerris, the first pair is raptorial; 

 the middle pair is used in propulsion and the hind pair as a 

 rudder. Of the non-gerrine forms, the modified land bugs, 

 so to speak, Hydrometra walks on the surface, as do Mesovelia 

 and the Hebrides, or Naeogeidce. None of these should in any 



