396 youj-nal of Couiparative Neurology a?jd Psychology. 



('81, p. 262) showed that, under certain conditions, Lasius niger 

 will move a short distance along an unscented path. Wasmann 

 ('01), although believing that the footprints possess an odor-shape 

 which enables ants to tell which way to go, gives several examples 

 of ants going a short distance along paths that have not been 

 scented with their trail. Vielmeyer ('00), in his study of Lepto- 

 thorax unifasciatus, claims that, when near the nest, light and 

 shadows assist the ants in finding their way, and more than twenty 

 years before that Lubbock had stated that "In determining their 

 courses ants are greatly influenced by the direction of the light." 

 PiERON ('04), although admitting that odors play an important 

 role in the life of ants, was influenced by his discovery that ants 

 sometimes move along paths that have not been scented by trails 

 to conclude that odors play no part in guiding them home. Ac- 

 cording to him, their home-going is controlled by a tactile sense 

 and muscular memory. 



As far as I can understand Pieron, his hypothesis is as follows. 

 On the outgoing trip the muscular movements made induce in 

 the nervous mechanism a condition which enables the ant to 

 return to the nest, in a reverse order, over the same pathway by 

 which it journeyed forth. That tactile impressions are, and that 

 muscular impressions may be, factors in the impression that guides 

 ants harmonizes with my experiments; but that the muscular 

 movements play any such role as is here indicated seems improb- 

 able. Pieron's hypothesis implies that an ant returns to its home 

 in practically the path by which it went out. I have conducted 

 a large number of experiments which show conclusively that this 

 is not always the case. 



1. I have already mentioned the case of the ant which would 

 drop, with a pupa in its jaws, from the stage to the island; but 

 which, on returning from the nest, would wander about the island 

 until I presented a pair of forceps. It would then mount the for- 

 ceps and rest quietly thereon until I had placed the tip of the for- 

 ceps on the stage. It would then step off^ and pick up a pupa 

 and take a flying leap from the stage to the nest. 



2. I had a specimen of Formica fusca var. subsericea Say, 

 which regularly descended from the stage to the island on the 

 under side of the incline, but on returning to the stage this ant 

 always moved along the upper side. 



3. Another specimen regularly descended to the island by way 



