170 MR. D. SHARP ON THE EESPIRATOBT 



Again ascended at 4.43, but only remained for about 2 seconds. 

 Observation ceased at 4.53. 



No. 2. Sept. 12.— Began to watch at 4.5 p.m. At 4.8 tbe H. 

 pictus I'ose to the surface for an instant only, but did not not do 

 so again, although close attentiou was given until 5.45 p.m. 



No. 3. The same night. — At 9.19 p.m., waited for ten minuter 

 before an ascent was witnessed. The journeys for air succeeded 

 as follows : — 



Rose at 9. 2 for 1 second. 

 ,, 9.37 „ 2 seconds. 

 9.45 „ 1 second. 



Rose at 9.54 for an instant. 

 „ 10. 4 for 1 second. 

 10. 9, obs. ceased. 



These observations were made by lamplight. It is possible the 

 insect was incommoded by the light ; it was less quiescent than 

 in the afternoon, making short excursions about the water when 

 it came for breath to surface. 



Movements much quicker than those of Sydrovatus. 



No. 4. Sept. 26th. — When first attention was drawn, viz. at 

 1.31 P.M., the beetle was under cover. It rose, however, to per- 

 form aeration at 2.3 p.m. for 1 second, then it descended and lay 

 concealed as long as the observation lasted, up to 2.31 p.m. 



No. 5. Same night. — At 9.11 proceeded to watch by lamplight. 

 At 9.24 this a. pictus ascended for an instant, again at 9.44, and 

 again at 10.1, also for an instant. I stopped observing at 10.11 



P.M. 



Minutes Seconds 



of obs. Ascents. at surface. 



98 2 3 



100 1 1 



50 5 6 



60 1 1 



60 3 3 



Totals 5 368 12 14 



Summary. — It appears that this very small species rises once in 

 30| minutes, and remains at surface about 3 seconds ; and the time 

 it is exposed bears to the time it is concealed a ratio of 1 : 1577. 

 It would seem that it takes in its breath very rapidly ; for it was 

 never observed to remain at the surface more than 2 seconds, 



VI. Htdropoeus GtTLLENHALLI. 

 No. 1. October 10th. — Beetle of doubtful sex, concealed when 

 observation commenced, 3.41 p.m. But it rose at 3.59 for 1 second 



