HUNGERFORD: AQUATIC HEMIPTERA. 25 
a new generation of water bugs. True, many of the bugs an- 
ticipate this, especially the Corixids, and many of the back- 
swimmers are tardy, but as a whole, when the cattails bloom, 
adults of the spring generation of water bugs are at hand. 
For days the water had been surveyed for eggs, but none 
found until on June 17. Corixid eggs were present in num- 
bers. Now, indeed, the days of the pool are numbered, the 
cattails are steadily encroaching from the west end, and the 
spike rush bunches are advancing. This restricts the range 
of true aquatics, but leaves the marshtreader and Mesovelia 
dominant above. A rain enlarged the pool a few days later, 
but did not change the circumstances of the life above or 
within, and after a few days the recession of the pool was 
resumed. July 8 the water extended only to the edge of the 
great cattails. Eggs of Corixids and Notonectids were now to 
be seen again, and the surface was surveyed by both the 
striders and treaders in numbers. 
Surely there must be some truce among these keen com- 
petitors of the surface! For here they are all eager for food 
and not one with scruples against pouncing upon a weaker 
brother, yet getting on together—a heterogeneous collection 
from the large Gerrid to the tiny Microvelia. How they man- 
age to maintain an armed truce and survive by their alertness 
only patient observation can discern. 
How often have we been able to study the undisturbed pop- 
ulation in the early morning hours when food getting seemed 
their chief concern! There were the nervous jerky-gaited 
Gerris nymphs, the agile Mesovelias and the deliberate, stalk- 
ing Hydrometra. The Gerrids are truly powerful enough 
and quick enough to clear the waters of their competitors! 
Why do they not do it? Because, if we may judge from their 
behavior, there is some mutual aversion that is overcome only 
by an occasional ravenous appetite. On several occasions, 
when some bug was intent upon an activity that distracted its 
usual vigilance, it was caught by a larger bug only to be re- 
leased again without apparent injury. The capture of a pair 
of mating Hydrometra by Gerris marginatus and their sub- 
sequent release is a fair illustration. Mesovelia females at- 
tacked while ovipositing were invariably released unharmed. 
Many instances of the stealthy approach of some predator with 
ill intent to its prey have been watched with fear for the 
