44 THE UNIVERSITY SCIENCE BULLETIN. 



appended no bibliography and gave no hint of an acquaintance 

 with the significant results of the recent European workers. 

 His classification of respiratory types, however, is fairly stated 

 if his interpretation of function be ignored. 



I. Dorsal reservoir: Corixidae, Belostomatidse and Naucoridae. 

 II. Abdominal channel: Notonectidse. 

 III. Tube type: Nepidae. 



The Corixidae make contact with the air by the thorax, while 

 the Naucoridae and Belostomatidse connect with the tip of. the 

 abdomen, as do the Notonectidse and Nepidse. The last named 

 family have prolongations of the eighth abdominal segment, 

 which afford a connection between the air and the spirac- 

 ular openings, enabling these insects to remain at some dis- 

 tance below the surface. 



In matters of meeting the problem of air supply the Co- 

 rixidse, though less profoundly modified as to structure than 

 the Nepids, are nevertheless the most independent in their be- 

 havior of all the water bugs. The problem of aquatic respira- 

 tion then is a complex one, and involves further study. 



There is yet another phase of hydrobiology that should be 

 mentioned in connection with this chapter. It is the mastery 

 of the physical properties of the water relating to the surface 

 film. Brocher has given us a splendid paper on the funda- 

 mentals of this question, to which the reader is referred. He 

 shows the clever devices that enable insects to walk upon the 

 water, to rise out of the water, to break the surface film from 

 below in making contact with a vital supply of free air, as well 

 as to enter the water from above. 



It is interesting to watch a Notonectid just alighted upon the 

 water maneuver to submerge. Encased in nonwettable ma- 

 terial, the body is buoyed up, and to submerge, the tip of the 

 hind limb, which is wettable and attracts the surface film, is 

 dipped into the water before the head and the film drawn thus 

 over the back, covering the bug and placing him below. In 

 the light of Brocher's work, there are many interesting experi- 

 ments that suggest themselves concerning the manner in which 

 the water bugs have met and solved the problems of their 

 elected environment. 



