Turner, Homing of Ants. 419 



yet the ant always went home without a moment's hesitation. To 

 say that the pupa does not give the ant a stimulus to make a cer- 

 tain definite movement, but any movement necessary to take it 

 home, is equivalent to saying that the ant responds to the stimulus 

 as a means to an end. 



There is yet another observation which deserves mention in this 

 connection. In all my experiments with ants working in concert, 

 when the pupae had all been removed from the stage the ants would 

 thoroughly search the stage and mcline and then retire to the nest. 

 Why did the ants stop going to the stage ^ Surely the same stimuli 

 existed in the nest as formerly; the only new factor is that there are 

 no more pupae on the stage. This cessation of movement cannot 

 be attributed to fatigue, for they act in the same manner after 

 removing a small lot of pupae as they do after removing a pile 

 many times as great. It would be equally fallacious to assume 

 that the pupae on the stage influence the ants directly from afar, 

 and that the lack of pupae to furnish an immediate stimulus is 

 the cause of the cessation; for ants roaming over the island in 

 search of pupae are not attracted by the pupae. Many a time I 

 have seen specimens of Lasius, and Formica pass repeatedly back 

 and forth beneath the stage without being attracted by the pupae 

 on the stage; I have known Formica to ascend the incline and pass 

 to within three centimeters of the pupae and return to the island 

 without sensing them. To test whether such ants were in a con- 

 dition to be affected by the sensing of pupae, I have placed pupae 

 in front of them as soon as they reached the island. Immediately 

 such pupae were picked up and carried to the nest. Nor would it 

 be consistent to assert that the stimulus-to-return did not affect 

 ants that returned unburdened to the nest; for after the pupae were 

 removed, each ant always made from one to a few round trips; 

 and, furthermore, it frequently happened, when the stage was well 

 supplied with pupae, that an ant would pass, unladen, to the nest, 

 and then immediately, or after a few moments, resume its period- 

 ical round trips. 



I fail to see how these facts can be harmonized with either the 

 assimilation hypothesis of Thorndike or with the determination 

 of stimulus hypothesis, but they do harmonize with the assump- 

 tion that ants have associative memory. It is not claimed that 

 ants exhibit a high grade of intelligence in finding their way about. 

 In my experiments, the first trip to the nest was always the result 



