POWER OF RECOGNITION AMONG ANTS. 233 



or antagonism is always shown ! by the younger ants, toward 

 the older, if the ants be of the same colony, and if the young 

 ants have been guarded from association with ants older than 

 themselves. 2 



Experiment &--On July 18, 1904, I put into the nest of two 

 segregated workers of the N colony, hatched from cocoons taken 

 from the wild nest July 28, 1903, and at the time of this ex- 



1 In all experiments here recorded, unless a contrary condition is indicated, the 

 ants whose recognition of a visitor was in question had in their nest inert young that 

 had engaged their attention during several previous days. The action of resident 

 ants toward a visitor is much more prompt and decisive when there are larvae or 

 pupre in the nest. 



2 In experimenting with ants, a third source of individual odor, not set forth in this 

 paper, although always reckoned with in the experiments, lies in the other ants with 

 which the individual associates. This odor appears and disappears with certain ex- 

 ternal conditions. Ants take on the odor of their associates in a mixed nest, and 

 this incidental odor usually disappears after about ten days of isolation, the inherent 

 odor then reasserting itself. Ants may be smeared with the juices of ants of another 

 species or colony and may thereby become immediately subject to attack from com- 

 rades from whom they have been but momentarily removed. 



I have lately submerged ants for eighty hours or more in distilled water at a tem- 

 perature of 10 C. , putting two species or two colonies into the same water, using 

 thirty-five cubic centimeters for a dozen ants, and I have found that the ants of each 

 species or colony, when revived and returned to their former nest, were attacked as are 

 enemies, and that ten days proved to be an insufficient time for the reassertion of the 

 inherent over the incurred oder. That these attacks from comrades were due to the 

 alien odor acquired in the water and not to some other cause, was shown by the fact 

 that when similar ants were likewise submerged in unmixed groups, the returned 

 ants were amicably received by their former comrades. 



I thus submerged, in thirty cubic centimeters of water, three Cainpouotiis pictus 

 and fifteen Steuanuna fithniui, for eighty hours. One of the Camponotus revived, 

 and a day later I returned it to its three former comrades, employed in the care of 

 cocoons in a small Fielde nest. The three instantly attacked the one, and would 

 doubtless have slain it had I not interfered. Having rescued, I isolated it for ten 

 days in a Petri cell, and then again returned it to its former nest. Two of the three 

 resident ants at once attacked and killed it. Of the Stenammas several revived, and 

 on my returning them to their former nest, they were all killed by their quandam 

 associates. 



Of four Stenammas that revived and recovered after eight days submergence in com- 

 pany with five Camponotus pennsylvanicus, three were killed by former comrades on 

 my returning them to their nest. One of the four was isolated by me, in a Petri cell, 

 for twenty days before I returned her to the nest, and there the returned ant was for 

 some minutes the center of an examining circle of many ants. A day later she was 

 being dragged by two workers, but she was ultimately restored to good standing in 

 the nest. 



It is interesting to observe the puzzled or critical demeanor of an ant engaged in 

 ascertaining whether a new-comer has an incurred or an inherent foreign odor. 



