hungerford: aquatic hemiptera. 177 



B. Biology of the Notonectid^. 



General Notes. Of all our American water bugs none are more gen- 

 erally known in their native haunts than the back-swimmers. They are 

 to be found in nearly every pool and pond, and afford most interesting 

 objects for aquarium study. The fact that they swim on their backs 

 readily distinguishes them from all other water bugs. 



Some of them spend much of their time hanging, back downward, just 

 beneath the surface film, the tip of the abdomen in contact with the sur- 

 face, the body, head downward, at such an angle that just the claws of the 

 intermediate limbs may touch the surface and the hind limbs directed 

 well forward of right angles to the body poised for a sudden rowing 

 stroke. This, in fact, pictures our best known, and most widely dis- 

 tributed Notonecta undulata. Others prefer to float submerged in open 

 water or cling to the shelter and shade of aquatic vegetation. 



The predatory tendencies and daring attacks of these insects upon 

 other animals of formidable size have been known from the first bio- 

 logical notes concerning them. Records of the capture of fish and various 

 insects, mature and immature, by members of the genus Notonecta are 

 common. However, the intimate ecological connection of these insects 

 with the life of the pool lies in the fact that a large part of the food of 

 the young of all of them, and the adults of Buenoa and Plea, consists of 

 Ostracods and other small Entomostraca. 



The adults of all the species observed in this country pass the winter, 

 either hidden in the mud and other debris of the pool or remain more 

 or less active, as conditions may permit. They have been observed swim- 

 ming beneath the ice in spring-fed pools in midwinter. 



Mating occurs beneath the water in spring, and the females deposit 

 their white oblong-oval eggs, either attaching them by means of a water- 

 proof glue to the surface of sticks and brush in the water, as in the case 

 of most members of the genus Notonecta, or inserting them in the tissues 

 of water plants and the like, as in the case of Plea, Buenoa, and Noto- 

 necta irrorata. 



There are one or more generations, depending upon the species and 

 the climate. 



The details of life history and behavior are treated under the notes 

 concerning the various species. 



Biological Notes on Plea striola. 



Aside from a few notes on habitat, little has been written regarding 

 the biology of our tiny back-swimmer. This little fellow has been taken 

 in tangles of aquatic vegetation, such as Elodea, Chara and the like, in 

 widely separated parts of our country. Van Duzee lists it as occurring 

 in the following states: Kansas, New York, New Jersey, Florida, Illi- 

 nois, Texas, Iowa, Massachusetts and California. 



Even the suggestion concerning its feeding habit which has crept 

 into a recent text on aquatic biology — information taken from a pub- 

 lished inference to be sure — is erronous. The author of the suggestion 

 that Plea apparently subsisted upon the juices of the plants, based it 



12 — Sci. Bui. — 1669 



