94 The Animal Mind 



vision than Lasius fuliginosus, which is guided largely by 

 smell (325), and the same conclusion is reached by Was- 

 mann (426). Pieron calls attention to still another factor 

 which he calls muscular memory, influential in all the species 

 he tested, but especially so in Aph&nogaster barbara nigra. 

 If an ant of this species is returning to the nest and steps on 

 a bit of paper covered with earth, she may be moved bodily 

 to some distance without seeming to notice the fact. In such 

 a case, on being set down, she continues her march "in the 

 new region, following a direction absolutely identical with that 

 which she was following in her return to the nest, and she does 

 not stop or seem disturbed until after a more or less prolonged 

 march, often about equal to the distance that separated her, 

 at the moment when she was displaced, from the entrance to 

 the nest." Even if her displacement occurs near the entrance 

 to the nest, she will go on past it and stop at a distance about 

 equal to that which she would ordinarily have had to traverse. 

 Evidently smell is not here concerned (325). The ant would 

 seem to be like a little machine wound up to go just so far 

 and to take just such turnings. We shall mention this 

 observation again in a later chapter. 



28. 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 found in 1886 that 

 ants of the genus Myrmica whose antennae were removed 

 would attack their own nest mates (130). It seems probable 

 that each nest of ants has a peculiar odor which is the basis 

 of the distinction between friends and foes. Bethe tested the 

 smell theory by dipping an ant first in weak alcohol, then 



