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 way to my ants. The 

 experiment was not, however, very satisfactory, as I was not 

 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 ; 



