BEES DO THEIR WORK 345 



must be almost infinitely tenuous. If, on the 

 other hand, the stimulus is due to the giving out 

 of waves or vibrations comparable to the waves 

 of light or of sound, the nature and other charac- 

 teristics of these manifestations of energy are 

 absolutely unknown." 



Another experimenter has shown that ants 

 will follow a trail that has been made by other 

 ants bearing honey or sugar. The inference 

 seems obvious that the ants are following a veiy 

 delicate trail by the sense of smell. But perhaps 

 it is well, considering the unrevealed nature of 

 the stimulus associated with odors, to adopt Pro- 

 fessor Loeb's cautious phrasing and speak of the 

 sense through which insects are guided to odor- 

 iferous objects as "chemical irritability." 



The fact that a bee is able to travel in a straight 

 line backward and forward between its distant 

 hive and the flower bed or the apple tree from 

 which it is harvesting, even though the distance 

 be a matter of miles, suggests the possession of 

 organs of sense of a far more delicate character 

 than our olfactory nerves. 



It is hardly probable that vision is an impor- 

 tant aid in these long-distance flights; for Pro- 

 fessor Loeb's experiments have led him to infer 

 that the dioptric apparatus of insects is very in- 

 ferior to the human eye. Moreover the flowers 



