186 LIMITS OF VISION. 
course be little, if any, doubt, that bees are capable of 
distinguishing colours; and I have proved experi- 
mentally that this is the case. Under these circum- 
stances, I have been naturally anxious to ascertain, 
if possible, whether the same holds good with ants. 
I have, however, found more difficulty in doing so 
because, as shown in the observations just recorded, 
ants find their food so much more by smell than by 
sight. . 
This being so, I could not apply to ants those 
tests which had been used in the case of bees, 
At length, however, it occurred to me that I 
might utilize the dislike which ants, when in their 
nests, have to light. Of course they have no such 
feeling when they are out in search of food; but if 
light is let in upon their nests, they at once hurry 
about in search of the darkest corners, and there they 
all congregate. If, for instance, I uncovered one of 
my nests and then placed an opaque substance over one 
portion, the ants invariably collected in the shaded part. 
I procured, therefore, four similar strips of glass, 
coloured respectively green, yellow, red, and blue, or, 
rather, violet. The yellow was rather paler in shade, 
and that glass consequently rather more transparent 
than the green, which, again, was rather more trans- 
parent than the red or violet. I also procured some 
coloured solutions. 
Prof. Dewar was kind enough to test my glasses 
and solutions with reference to their power of trans- 
