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 alge. 
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 New 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 fowing 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 
