HUNGERFORD: AQUATIC HEMIPTERA. 35 
As far as the true aquatics are concerned, according to the 
texts, which must of course rely largely upon the published 
records, one and all feed upon insects and other animals in the 
water. The tendency of the reader, however, is to gather the 
impression that the prey is large. This is not always true. 
The large Belostomatids, no doubt, consume considerable num- 
bers of snails, while the bulk of the food of the first three or four 
stages of Notonectz consists of small Crustacea: Ostracods, 
Cyclops and Daphnians with the addition of such other forms 
as they are able to master. In one genus of back-swimmers, 
the Buenoa, the adults as well as the nymphs, feed very largely 
upon small entomostracan forms. This is also true of the 
little Plea. Corixids on the other hand find the source of their 
food supply in the brown sedimentary material on the bottom 
of the pool. This they scoop up with the flat rakes of their 
forelegs. These rakes are somewhat spoon-shaped termi- 
nal segments or pale, which are most admirably equipped for 
their work. The details of the feeding habits of the boatmen 
are given elsewhere. It is only necessary to call attention here 
to the fact that they are not predatory in the ordinary sense, 
that they will strip the chlorophyl from a filament of the spiro- 
gyra quite as readily as to gather in the flocculent ooze of the 
bottom of the pool with its attending population of diatoms, 
desmids, Euglenz, Scenedesmus, organic debris, and the Pro- 
tozoa, rotifers and oligochetes it may contain. 
Thus the role played by the aquatic Hemiptera in the society 
_ of water forms indicates an intimate relation, not only to the 
larger beings, but to the smaller Entomostraca and even to the 
unicellular life of our ponds and pools as well. 
It is further to be noted that, while some, like the water 
striders and back-swimmers, many take advantage of help- 
: less terrestrials upon the water when opportunity affords, the 
_ water and its surrounding vegetation supply their chief de- 
mand. 
ECONOMIC IMPORTANCE. 
In these utilitarian days one is asked first of all in regard 
to the value of his results. If all could but have the vision as 
Professor Dawson has expressed it in a recent number of 
— Science !* 
* “University Ideals and ee Limitations,’ by Professor Perey M. Dawson, in 
Science, N.S., vol. XLVII, p. 54 
