28 Trans. Acad. Sci. of St. Louis 



The advocates of the homing instinct claim that there 

 is a peculiar inner power which guides insects home by 

 the shortest route. Recognition and memory play no 

 part whatsoever in this form of behavior. The insect 

 leaves home and forages here and there. When ready 

 to return, it instinctively knows in which direction and 

 how far to go. 



According to believers in the tropism theory, there is 

 some external stimulus or stimuli which forces an insect 

 homeward in the same manner that iron filings are 

 impelled to orient themselves and move toward a strong 

 magnet. This process is purely mechanical; it differs 

 from the above in the stimulus being external instead of 

 internal. 



The advocates of muscular memory insist that all the 

 time an insect is wandering away from home the move- 

 ments of the muscles and the stresses and strains of the 

 tendons are inducing in the nervous system a certain 

 form of tension. When the insect is ready to return 

 home, this tension is gradually released and induces the 

 insect to right-about-face and retrace its steps. 



Those who contend that there is a recognition of land- 

 marks insist that insects and men find the way home in 

 essentially the same manner; namely, by an associative 

 memory enabling the possessor to recognize landmarks. 

 This hypothesis differs from all the others in predicating 

 an intellectual factor. It presupposes that insects are 

 capable of learning by experience and profiting there- 

 from. 



ANTS 



BLave you ever watched long lines of ants move to and 

 fro between foraging grounds and nest? Have you ever 

 wondered what enabh>s them to find their way? Have 

 you ever speculated upon the psychology of their be- 



