hungerford: aquatic hemiptera. 21 



contained considerable growth of Spirogyra. One side was 

 bordered with spike rush, Eleocharis obtusa. This little pool, 

 a rod wide and perhaps three long, of clear, open water, proved 

 the best collecting ground of any of those studied. Hydrome- 

 tra martini, Microvelia borealis, Mesovelia mulsanti and Gerris 

 marginatus patrolled the waters and floating rafts of algae. 

 Arctocorixa alternata and Notonecta undulata were dominant 

 within the pool. Ostracods, the basis of the food supply for 

 the young back-swimmers and for the smaller surface forms 

 as well, were present in astonishing numbers. (See Plate I 

 for photograph.) The other pool, called the Rock Pool was 

 roughly a rod square and contained no vegetation save a mar- 

 gin of spike rush and sedge, the outermost procumbent stems 

 of which floated upon the water and made footing for the 

 Mesovelias that dwelt about the pool. The water soaked stems 

 of this rush were, more than those of any other, employed by 

 the Mesovelias in oviposition. This pool contained many Co- 

 rixids but fewer back-swimmers than the Cattail Pool. 



All of these pools, save the first, are within five minutes ride 

 from the writer's residence, and were visited several times a 

 week throughout the season. 



Several other bodies of water, the Brick Plant ponds and 

 Bismarck Grove pond, were surveyed frequently. These 

 waters occupy several acres in extent, are devoid of vegeta- 

 tion, and afforded less satisfactory studies than the smaller 

 pools. They are shown in the photographs, Plate I. 



Central Neiv York. 



The principal waters studied were within easy reach from 

 Cornell University. Since the true water bugs are seldom 

 found in running waters, the frequent surveys were confined 

 to the quiet waters. 



The Field Station: This is located in the marshy meadows 

 at the south end of Lake Cayuga. It is surrounded by a sys- 

 tem of pools, some isolated, others connected by outlet to the 

 lake. The isolated pools were newly made and contained few 

 bugs, other than the back-swimmers. One pool, close by the 

 station, was fed by a f owing well and its waters contained 

 quantities of Elodea and other aquatic plants. This pool was 

 open most of the time throughout the winter, and was ever a 

 place to collect water bugs in great numbers. Four species of 



