i68 
NATURE NOTES 
These experiments show that ants notice a rise of tempera- 
ture of ’4° C., at the most ; for if ants did not go under for the 
sake of the extra heat, they must have gone under (i) for shade, 
(2) by accident, or (3) by instinct. 
(i.) {a) If they went under for shade, then they would remain 
under and not come out. 
[b) Also they would have gone under in the first experiment, 
when the water in the cell was at the temperature of the air ; 
but they did not do this. 
(ii.) One reason (a) of the above fact that they went under and 
came out again seems at first sight to support the argument that 
they went under by accident, but to any one who has actually 
watched the experiments the possibility is quite contrary to 
reason. 
(iii.) This argument assumes that they noticed the difference 
of 6'6° C. experienced in the first experiment, and that they went 
under in the following experiments because they knew that the 
portion under the cell, which presumably they saw, was hotter 
than the surrounding portions. This argument, then, says that it 
is not conclusively proved that ants feel a difference of tempera- 
ture of '4° C. or less, but that they do feel a difference of '66° C., 
the difference of temperature experienced in the first experiment. 
In order to test this I placed the whole nest inside a dark 
cupboard in a dark cellar so that no light was admitted even 
when the door of the cupboard was opened. 
(6) At 6.10 p.m. : In the same way as before I filled the cell 
with water and warmed it by adding strong sulphuric acid drop 
by drop until it was exactly i4'7° C., i.e., exactly 1° C. above the 
temperature of the surrounding air. Then taking the cell, and 
switching off the small 4-volt lamp — which I used to read the 
temperature with — I placed it on a part of the nest where I knew 
there were no ants. At 6.23 p.m. there were six ants under. 
At 6.28 p.m. all these went out again. 
(7) Repeated: At 6.30 p.m., temperature of air 13-7° C. ; tem- 
perature of water i6'0° C. ; therefore difference of temperature 
2-3° C. 1 placed the cell on the nest as before, but there were 
five or six ants under. At 7.30 p.m, there were half the pupae, 
and about seventy ants under. The temperature of the water at 
7.30 p.m. was i3'9° C., i.e., only -2° C. above the temperature of 
the air. In all probability there were more under at about 7 
o’clock, but unfortunately I was unable to look at that time. 
(8) Repeated: At 7.37 p.m., temperature of air i3’7° C. ; 
temperature of water i5‘g° C. ; difference of temperature 2-2° C. 
I placed the cell quite 4 ins. away from the nearest ant. At 
8.10 p.m. there was one worker under. Evidently this absence 
of ants was due to their not feeling the heat at such a grea 
distance. 
(9) Repeated : At 8.15 p.m., temperature of air 137 ' C. ; 
temperature of water 167° C. ; therefore difference of temperature 
3° C. This time I placed the cell between two piles of pupa.'. 
