ACTION or THE CARNITOROtJS WATER-BEETLES. 



181 



The male. 

 Rose at 9.21 for 4 minutes, 

 but only occasionally breathing. 

 Eose at 9.35 for 15 sees. 

 9.40 „ 100 „ 

 9.53 „ 65 „ 

 „ 10. „ 50 „ 

 » 10. 5 „ 105 „ 



The female. 

 Eose at 9.37 for 35 sees. 

 „ 9,57 „ 35 „ 



Observation ceased at 10.37, 



Summary. — The species rose, on an average, about once in 25| 

 minutes for breathing, and remained, on an average, nearly 70 

 seconds at surface for each respiration. The longest interval 

 observed between two respirations was 52 minutes, and the du- 

 ration of a respiration varied from 5 to 105 seconds. The 

 time it was exposed for breathing bore to the time it was not so 

 exposed a ratio of 1 : 22^. It appears probable that the species 

 is more active by night than by day, and that the male is more 

 active than the female, 



XYI. Dytiscus marginalis. 



No, 1. Aug. 2nd, 1874. — Observation commenced at 7 o'clock 

 y.M. on one ^ individual of this species. 



Eose at 7.56 for 70 sees. 

 „ 8. 2 „ 40 _ „ 

 „ 8. 9 „ an instant. 

 „ 8. 9 „ 30 sees. 

 „ 8.15 „ 300 „ 

 „ 8.22 „ 65 „ 



Observation ceased at 8.23 p.m. 

 No. 2. Aug. 9th, 1874. — Observation commenced at 3.40 p.m., 

 on two males of D. marginalis. 



Eose at 3.48 for 15 sees. 

 „ 3.48 „ 20 „ 

 ,, 3.51 ,, o „ 



Eose at 4.22 for 50 sees. 



„ 4.22 „ 60 „ 

 ^ ,. 4.24 „ 5 „ 



T.INN. JOURK. — ZOOLOGT, VOL. XIIT. 



16 



