37^ 'Journal of Comparative Neurology and Psychology. 



conclusion that odors play a part in the life of ants, but that it is not 

 by them that ants are guided on their journeys.^ This is a much 

 broader statement than that made above; indeed, it seems much 

 broader than either his or my experiments warrant. Even though 

 ants, favored by the muscular and tactile impressions furnished by 

 the mandibles and feet, can still move with much precision when 

 deprived of the use of eyes and antennae, yet we have no more 

 right to say that light and odors play no part in the home-going of 

 normal ants than we have to say that, because blind men can move 

 with much precision to and from home, vision plays no part in the 

 home-journey of the normal man. What his and my experiments 

 demonstrate is that odors do not play the sole role m the home- 

 going of ants. 



II. EXPERIMENTS ON THE HOMING INSTINCT. 



Most educated people once believed and many untrained people 

 still think that there is a mysterious power, the homing instinct, 

 which unerringly guides certain animals on their journeys. This 

 "power" differs from a tropism in being guided by an inner rather 

 than an outer stimulus. It was my purpose in the experiments of 

 this chapter to discover whether ants possess a homing instinct. 



The fact that ants lose their way militates against the idea that 

 they have a homing instinct. Many a time after a rain, I have 

 caused ants to lose their way by placing them and their pupae on a 

 stone situated within a few feet of their nest. At times the whole 

 lot would roam aimlessly about; more often a portion would roam 

 at random while the rest would busy themselves placing the pupae 

 under the stone on which I had placed them, or else under any 

 other cover that they happened across; at yet other times a portion 

 would finally reach the nest, while the rest would wander off. 



finally some would strike the trail and the line of march would be renewed. (2) He moistened the path 

 with a decoction of ants from an alien colony. The ants retreated precipitately. (3) He moistened the 

 path with pure water. It had no efTect on the ants. (4) He brushed odoriferous herbs across the path. 

 The ants hesitated a moment then passed on. (5) He displaced the dust of their path with a twig. 

 They were not disturbed. (6) He placed a piece of paper across the path of home-going ants. On this 

 paper he scattered bits of turf and other detritus. When an ant had mounted this trap, Pieron gently 

 transported the whole to a new situation in a place similar to the path along which the ants had been 

 moving. In each case the ant continued in the direction it was going for a distance about equal to that 

 between the trap in its original position and the nest opening. 



^ According to my understanding, Pierqn's conclusion is so out of harmony with what his experiments 

 warrant, that I have thought it wise to give, in this footnote, his exact words: "On en peut conclure que 

 I'odorat doit jouer un role dans la vie de ses fourmis, mais ce n'est pas sur lui qu'elles se guidant dans 

 leur passage." Loc. cit., p. 176. 



