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 Notonectae 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-s\^immers, 

 the Biienoa, the adults as well as the minphs, 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 palse, 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 predatoiy in the ordinary sense, 

 that they will strip the chlorophyl from a filament of the spiro- 

 g\-ra quite as readily as to gather in the flocculent ooze of the 

 bottom of the pool with its attending population of diatoms, 

 desmids, Euglen^e, Scenedesmus, organic debris, and the Pro- 

 tozoa, rotifers and oligochsetes 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 their Limitations," bv Professor Percv il. Dawson, in 

 Seietice. X. S., vol. XLVTI. p. 547. 



