1901.] NATURAL SCIEXCES OF PHILADELPHIA. 539 



when all of its body except the head aud one pair of legs has 

 been clipped off. I have seen an ant, deprived of the smell-sense, 

 continue through eighteen hours its grip upon an adversary's 

 antenna. An auteunaless ant will fight with energy and endur- 

 ance, the difference between its battles and those of a whole ant 

 being in that it fights indiscriminately the ants of its own and 

 other colonies. In the complete ant the odor appears to modify, 

 control or determine the fighting reflex. 



In all cases of transfer from one kindred group to another there 

 are evidences that the whole ants discern differences in the indi- 

 viduality of their companions whether queens or workers. Every 

 newcomer is examined, sometimes from end to end, by touches of 

 the antennae; there is often much hesitating and tentative nabbing 

 of an ant that is ultimately received into full fellowship, and two 

 or three impetuous onsets often precede complete filiation. 



In determining through their actions the affinities and repulsions 

 of the ants, I have considered final relationships more important 

 than first behavior. 



The removal of the antennae does not destroy the odor of the 

 ants so maimed, for neither their enemies nor their kindred 

 change on this account their usual behavior toward them. But 

 the excision of these prominent organs reduces greatly their 

 liability to seizure. 



The commingled odors of all the ants in the nest constitutes what 

 Bethe calls the Neststoff, or what I shall call the aura of the nest. 

 It is diffused in air or ether from the animate occupants of the nest, 

 and it is discerned by the ant through the twelfth, the distal, segments 

 of her antennce. 



By this aura every ant recognizes its own abode and distinguishes 

 it from the abode of other colonies. The aura of the nest may be 

 superadded to, but does not extirpate, the individual scent nor the 

 inherent body odor. 



The creation of a new nest-aura is always possible through the 

 gradual admixture of different odors produced by and disseminated 

 from living ants reared from eggs, larvae or pupse of alien colonies. 



Any ant bearing the preponderating odor is apt to gain easy 

 admission to the nest. The countless variations observed in the 

 treatment of newcomers are due to the infinitely variable propor- 

 tions in the odors borne by the ants. If an ant permanently bears 



