26 THE UNIVERSITY SCIENCE BULLETIN. 



safety of the unwitting victim only to see the incident close 

 without an actual attack or with but a brief retention of the 

 captured. 



But the above note is beside the issue, and should, perhaps, 

 have been omitted along with the many interesting incidents 

 recorded in the field notes that can find no place in the printed 

 record. 



It was noted on July 8 that the pool was restricted by the 

 great cattails on its western margin. By July 14 it was reduced 

 to a few little puddles in depressions made by boot tracks on 

 former visits. Hundreds of little Microvelias, Mesovelias and 

 a num.ber of Hydrometra had followed the waters to these re- 

 treats. Saldids were present upon the moist ground round 

 about, while within the water a few Corixids and Notonectids 

 still managed to survive in the ever diminishing quarters. The 

 following day one puddle of water yet remained, a little patch 

 of surface 6 by 10 inches, and upon it crowded together thir- 

 teen adult G. marginatus, a myriad of winged Mesovelia and 

 a host of Microvelia in all stages. They were making their last 

 stand upon the element that bound them together in common 

 interest. The end of it all was very near. Whither would they 

 go when the last drops sank into the ground, or were taken 

 up by the sun's hot rays? The writer wanted to know. The 

 back-swimmers and boatmen were gone, and even the nymphs 

 disappeared without leaving a carcass. What became of them ? 

 There is no clue. Perhaps the adults flew to other quarters 

 while the nymphs in their close confines fell the prey to sur- 

 face forms. There was only one other possibility, and that a 

 small one. Had the nymphs buried themselves in the mud? 

 To find the answer to this, on July 21, when all the water was 

 gone, the place was visited with a horse and wagon and the 

 mud from the bed of the pool placed in tubs and taken to the 

 laboratory. No living thing was likely to escape, for the mud 

 was only 6 inches deep upon a base of lime stone. Live ostra- 

 cods were numerous beneath the wet cattail leaves that were 

 prone upon the mud, but no true aquatics in evidence, nor yet 

 their eggs. About the young cattail clumps a few Hydrometra 

 lingered, but the abundant life of a few days previous was 

 gone, leaving no trace of its going nor making any provision 

 for a repopulation by its progeny should timely rains revive the 

 place. No eggs hatched from the rushes or cattail brought in 



