THE SENSES OF ANTS 
167 
nest of Lasiiis niger, the common garden ant, making sure that 
there were no ants under it. At ii. a.m. there were still 
none under. At 11.30 a m. there was one under, but he was 
moving about, and so was probably under by accident. On 
repeating this several times with the ditch full of water at the 
temperature of the air, I found that the results were always 
the same, viz., none went under. 
(2) October i, 1904, at 12.30 p.m., I warmed the water in 
the cell by adding three or four drops of sulphuric acid, and 
then placed the cell on the nest as before, making sure there 
were no ants under ; the water being now at a temperature of 
20'^ C., and the temperature of the air being i3'4° C. ; there 
was thus a difference of temperature of 6-6^ C. At 1-55 p.m. 
there were about 250 ants under, together with all the pupae, 
larvae and eggs. The pupae, it may be well to remark were 
always carried under first, secondly the eggs, and finally the 
larvae. 
(3) October 2. 1904, 2.45 p.m., repeated. Temperature of 
air 137“ C.; temperature of water i5'3° C. ; therefore difference 
of temperature i-6° C. At 2.50 p.m. there w’as one pupa, one 
larva, one female, and two workers under. At 3.15 p.m. these 
all went out again. The temperature of the water at this time 
vvas 14-1° C., i.e., only -4° higher than the temperature of the 
surrounding air. 
(4) At 3.35 p.m. repeated. Temperature of the air i3‘8° C. ; 
temperature of the water i7'05° C. ; therefore difference of tem- 
perature 3‘25° C. At 3.50 p.m. there were about seventy ants 
under, si.xteen pupae, seven or eight larvae, and half the eggs. 
At 4'2o p.m. there were about 250 ants under, all the pupae, half 
the larvae and half the eggs, the temperature at this time being 
14-4° C., i.e., a difference of ‘6° C. At 4.30 p.m. they were nearly 
all out again, except a few workers and larvae ; the temperature 
now being 14-2'^ C., i.e., a difference of -4° C. [It will be noticed 
from the last two experiments that the ants go out from under 
the cell when the difference in temperature between the water 
and the air is less than -4° C., less by reason of the loss of heat, 
owing to its absorption by the glass on the bottom of the cell 
and by the fine glass cover of the nest. But when the difference 
is '6° C. the ants continue to gather under it, and only depart 
when the temperature has lowered itself ’2° C. more.] These 
two experiments, repeated between twenty and thirty times, are, 
to my mind, sufficiently convincing proof that ants are suscep- 
tible to a change of temperature of at most ‘2° C. 
(5) At 4.30 p.m. I placed the same water (temperature 
14*2° C.) ins. to the right, where there were about seventeen 
ants under it. At 4.45 p.m. there were twenty-two ants under ; 
at 4‘47 p.m. two pupae were carried under. The difference in 
temperature now was at the most ‘4° C., and was probably not 
more that -35° C., owing to the reasons stated above. At 5-45 
p.m. there were none under, the temperature of the water being 
the same as that of the air. 
