ACTION or THE CAllNITOKGUS WATEB-BEETLES. 169 



Totals... 5 368 26 198 



Summary. — Hyphydrus ovatus, female, conceals itself beneath 

 stone or weed ; it rises to breathe on the average once in 14^ 

 minutes, but has been observed to be one hour without breathing ; 

 the time it remains at surface varies from an instant to 25 seconds, 

 and is to the time it is concealed in the ratio of 1 : 111*5. 



This species is probably more active at night than during the 

 day. It is a rapid and energetic swimmer. 



IV. HtDBOPOEUS INjEQUALIS. 



No. 1. Oct. 10th, 1875. — Observation commenced at 3.41 p.m., 

 the beetle concealed. It, however, rose at 4.10, and remained 

 under atmospheric influence for 5 seconds. Again, 4.39, for 2 

 seconds ; the observation closed at 4.41 p.m. 



No. 2. Same evening, 9.14 p.m., by lamplight, S. incequalis 

 being then hidden ; but it rose to the surface at 9.27, remaining 

 5 seconds, and again at 10.8 for the interval of 5 seconds. At 

 10.14 left off watching. 



Totals 2 120 4 20 



Summary. — Only two observations made, from which it appears 

 that this insect rises once in 30 minutes, and remains at surface 

 about 5 seconds, and the time it is exposed bears to the time it is 

 concealed a ratio of 1 : 360. 



Y. Htdroportjs picTtrs. 



No. 1. August 29th, 1875. — Obs. commenced 3.15 p.m. The 

 beetle was then quiescent under the edge of a stone ; at 3.46 came 

 up to breathe, but rapidly descended and became quiescent. 



