COMMUNICATING AND OTHER ANTS 69 



on emerging from N will proceed rapidly to B, but at 

 that point will be thrown into confusion and unable to 

 advance further owing to the gap in the scent between 

 B and A. 



Those who believe in the hypothetical sense of 

 direction, supposed to guide ants in their wonderful 

 journeys, might suspect that it was some strange 

 directive power, inexplicable to us, that impelled the 

 swarm along the true road. I do not think that this 

 is the case, for I placed a dead insect on the end of 

 a horizontal stick directed to the west and allowed the 

 worker, after making its discovery, to run back along 

 the stick on its way to the nest. Then, during the 

 absence of the worker, I rotated the stick in a semi- 

 circle so that it was directed to the east, but the 

 swarm on reaching the foot of the stick were not 

 confused ; they hurried along it without hesitation 

 though its direction had been reversed, 



I feel confident that their wonderful power of scent 

 is their true guide. No other explanation seems to fit 

 the facts. I think that the ants within the nest 

 recognize the distinctive odour of the worker that 

 brings the news, and can thus retrace the track which 

 that particular worker has followed. The information 

 which the returning ant communicates to its fellows 

 appears to be this, " I have found food ; retrace my 

 scent and you will find it." 



When observing the harvesters, I was driven to 

 the conclusion that each individual in the community 

 was capable of distinguishing its own odour from that 

 of every other individual in the nest and that, there- 

 fore, each ant must have a distinctive scent. Here 

 we are forced to a similar conclusion, for the swarm 



