Sensory Discrimination : the Chemical Sense 99 



straight to the mouth of the hive. He brings other evidence 

 against the vision hypothesis which we shall discuss in 

 Chapter XI. An unknown force, he concludes, guides 

 the bee in its homing flight (30). Von Buttel-Reepen 

 believes that visual memory will explain all the facts; 

 that the bees were not disturbed by the altered appearance 

 of their hive because they knew their way so thoroughly 

 that nothing could disturb them by the time they had 

 come so nearly home. The visual memory required is, he 

 admits, of a peculiar sort, which we shall consider in a later 

 chapter. The odor of the hive does cooperate with vision in 

 certain cases ; when a stock of bees has been moved without 

 their knowledge, they fly out without making any " orienting 

 flight," as they commonly do on leaving a new place, a fact 

 that is one of the evidences for the visual memory theory. 

 Nevertheless, many of them succeed in finding their way back, 

 and then, if their hive is placed among a number of others, 

 von Buttel-Reepen thinks they " smell" their way back to 

 the right one. He mocks at Bethe's unknown force, on the 

 ground that it must sometimes lead the bee to the hive and 

 sometimes back to the place where food has been found (72). 

 Bethe attempts to answer this by saying that the force acts 

 in cooperation with the physiological condition of the animal ; 

 the laden bee follows it to the hive, the bee with the empty 

 crop is led back to the food supply (32). Of course one may 

 say what one pleases about the modus operandi of an unknown 

 force without fear of disproof, but also without carrying much 

 conviction. 



.31. How Bees "recognize" Nest Mates 



The nest smell, which characterizes each hive and prevents 

 the reception of strangers, who are treated precisely after the 

 fashion of ants in similar circumstances, is composed accord- 



