BowDiTCH on Hydror/tdn'y obti'suta-s and Magdalis olyra. 5 



On May 16, I lost some larvae by cleaning my aquarium. 

 They do not seem to have groAvn much. 



May 18. The last three clays have Ijeen very warm and 

 the larvae have taken a fine start. They are so large as 

 not to be particular what they eat, l^ut chew up everything 

 in a most miscellaneous way. I can only find about six out 

 of the whole lot, and I suspect it is a case of the survival 

 of the fittest, for whenever by chance they happen to 

 meet a conflict almost always ensues ; they have given up 

 staying on top of the water, as they did at first, and pass 

 a o-ood deal of time on the bottom in semi-concealment, in 

 the thick weeds, or behind a stone. 



The third egg case which appeared six or seven days ago, 

 began to sink about the 15th, and by the 16th it w^as on the 

 bottom, and for no apparent reason. To-day however, it sud- 

 denly appeared again on the surface, and on examination 

 proves to have had an addition put to it of almost the same 

 size as itself This raising of an old egg case seems to show, 

 that the beetles knew tliat the eggs must be on the surface 

 in order to hatch properly, and therefore take the only 

 means in their power to get it back there, i. e. by adding to 

 it so as to make it again sufficiently buojant to float. It 

 would be interesting to test the truth of this theory by sink- 

 incr an eo-or case, and seeino; if it would hatch. 



For some unexplained cause or other my larvae all died, 

 so that I was unable to observe them further, and circum- 

 stances have not been favorable since then for a renewal of 

 my aquariiun. It will easily be seen that my notes on 

 eating out of the water need further investigation, and pos- 

 sibly the presence of Neuropterous larvae may have had 

 something to do with their disinclination to go beneath the 

 surface, though it is perfectly normal to find both sp cies 

 together. It may be that they only stay near and eat on 

 the surfiice, till they attain a certain growth. 



