382 Journal of Comparative Neurology and Psychology. 



in the hole at half past two o'clock. When the ant entered the 

 nest the clock struck three. A half hour to find a nest that was 

 only two feet away! 



It is believed that these experiments show conclusively that ants 

 do not possess a homing instinct. 



III. EXPERIMENTS ON THE POWER OF ANTS TO PROFIT BY 



EXPERIENCE. 



If ants are guided in their home-goings neither by tropisms nor 

 other forms of reflexes nor by a homing instinct, the probability 

 is that they learn the way home. To test this two classes of experi- 

 ments were performed. In the first class ants were allowed to 

 work in concert (which is the normal way); in the other class, 

 marked individual ants were induced to work alone or else in com- 

 pany with only one or two marked fellows. The cases where the 

 ants worked in concert will be discussed first. 



On the Lubbock island, which contained the nest of the colony 

 to be tested, was placed a new cardboard stage from which a new 

 cardboard incline led to the island. Ants and pupae were placed 

 on top of the stage. As a rule, the workers immediately began to 

 move about at random. Some species moved slowly others more 

 rapidly, and yet others so impetuously that many would fall off the 

 stage. Some carried pupae and others did not. 



After a lapse of time varying with the species examined (for 

 there is a marked contrast in the time it takes different species to 

 solve the problem) usually at least one of the ants would find the 

 way to the nest and back to the stage. As a rule it would carry 

 a pupa the first trip, but sometimes it would go to the nest unbur- 

 dened. The initial trip having been made, this ant would busy 

 itself conveying pupae to the nest; in this task it would soon be 

 joined by several or many workers. These recruits were made 

 partly from the ants on the stage and partly from ants roaming 

 from the nest. During the first few trips most species moved 

 slowly and cautiously as though they were feeling every step of the 

 way. Later, they moved much more rapidly. Sooner or later 

 (according to the activity of the species and the number of ants at 

 work) all of the pupae would be removed. In over a hundred experi- 

 ments no live pupae were left on the stage, excepting in cases where 

 the ants failed to find the way home (which happened occasionally). 



