loo The Animal Mind 



come, except that when the original path had crossed itself 

 in loops, the ant omitted the loops in her homeward way 

 (51). Apparently, however, many species of ants do not 

 thus retrace their own footsteps. The "muscular memory" 

 theory of Pieron (579) is based on the observation that if 

 a homing ant be carefully Ufted and deposited at a little 

 distance away, she will continue her course until she has 

 traversed a distance equal to that which she would have 

 had to go to reach her nest, if her course had not been inter- 

 rupted. Cornetz's theory (143, 144, 145), that an ant 

 has some mysterious power of retaining an impression of 

 the direction in which she set out, and of reversing this 

 direction when she is ready to return home, is derived from 

 a long series of very careful field studies. He reports 

 that a foraging ant takes a certain general direction and 

 makes excursions to right and left in search of food. When 

 the food has been discovered, she reverses her original 

 direction, but does not actually retrace any part of her 

 outgoing path. Pieron (591) is impressed by these obser- 

 vations, and inclined to think that a mysterious factor is 

 actually involved. That the direction of the light may 

 serve as a guide in the homing of ants is indicated by obser- 

 vations of Lubbock (441), Turner (722 a), and Santschi 

 (654), but the ability of ants to find their way about in the 

 dark is sufficient proof that it cannot be the sole factor. 



§ 26. How Ants "Recognize" Nest Mates 



Another problem of ant life to which smell appears to 

 furnish the key is that of the recognition of nest mates. 

 It has long been known that an ant entering a strange 

 nest, though of the same species, is likely to meet with 

 rough treatment, and even be put to death. Now Forel 



