WHETHER ANTS CALL ONE ANOTHER. 225 
came. We then allowed the ants which had fed to 
go home. From 3.30 to 4.30 twenty-eight came. 
From 4.30 to 5, fifty-one came. Thus in four hours 
and a half only seven came; while when the ants were 
allowed to return no less than seventy-nine came in an 
hour and a half. It seems obvious therefore that in 
these cases no communication was transmitted by 
sound. 
Again, Professor Tyndall was good enough to arrange 
for me one of his sensitive flames; but I could not 
perceive that it responded in any waytomyants. The 
experiment was not, however, very satisfactory, as I wasnot 
able to try the flame with a very active nest. Professor 
Bell most kindly set up for me an extremely sensitive 
microphone: it was attached to the underside of one of 
my nests; and though we could distinctly hear the ants 
walking about, we could not distinguish any other 
sound. 
It is, however, far from improbable that ants may 
produce sounds entirely beyond our range of hearing. 
Indeed, it is not impossible that insects may possess 
senses, or sensations, of which we can no more form an 
idea than we should ‘have been able to conceive red or 
green if the human race had been blind. The human 
ear is sensitive to vibrations reaching at the outside to 
38,000 in a second. The sensation of red is produced 
when 470 millions of millions of vibrations enter the 
eye in a similar time ; but between these two numbers, 
vibrations produce on us only the sensation of heat; 
