554 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 2 8 



(B) ODORS PLAY AN IMPORTANT PART IN COMMUNICATION 



Wheeler remarks that it is generally admitted that the segregatitm 

 of colonies of ants is caused by the presence of characteristic odors 

 which vary with the species, colony, and caste, and which, according 

 to Fielde, vary also with the deve^oiDmental stages of the individual 

 ant. Of course, the human nose can not detect all of these odors, 

 although Wheeler further says that even the degenerate human nose 

 can detect the different species of ants by their odors, and in some 

 cases even the different castes, but that the ants themselves carry the 

 discrimination much further. He believes that ants have not only 

 extremely acute powers of discriminating odors, but no less extraor- 

 dinary powers of associating them. He states that the human nose 

 can readily detect the pungent and ether odor of Formica riifa; 

 another species of ant has a smoky smell ; another smells like lemon 

 geranium or oil of citronella; another strongly like mammalian 

 excrement ; another less strongly so ; and another like rotten coconuts. 



Fielde claims that a certain species of ant bears three distinct odors ; 

 (1) A scent deposited by her feet, forming an individual trail, 

 w^hereby she traces her own steps; (2) an inherent and inherited odor, 

 manifested over her whole body, identical in quality for queens and 

 workers of the same lineage, and an instrument for the recognition 

 of blood relations; and (3) a nest odor, consisting of the commingled 

 odors of all the members of the colony, used to distinguish their nest 

 from the nests of aliens. Miss Fielde says that the odor of ants 

 changes with their age, and that " a cause of feud between ants of tlie 

 same species living in different communities is a difference of odor 

 arising out of difference of age in the queens whose progeny consti- 

 tute the communities, and difference of age in the ants composing the 

 community." She calls this odor the progressive odor, and further 

 claims that fear and hostility are excited in the ant by an odor which 

 has not been encountered and found to be compatible with the com- 

 fort of the ant. The same author calls the family or inherent odor 

 the specific odor wdiich is transmitted by the mother ant to all her 

 offspring of both sexes within the species. Miss Fielde claims that 

 ants not only differentiate the innate odors peculiar to the species, 

 sex, caste, and individual, but also the incurred odor of the nest and 

 environment; furthermore, that they can detect the progressive 

 change of odors due to change of physiological condition with the 

 changing age of the individual. She says that " as worker ants ad- 

 vance in age their progressive odor intensifies or changes to such a 

 degree that they may be said to attain a new odor every two or three 

 months." 



Judging from the experiments on ants made by various observers, 

 the family odor in these insects seems to play an important role by 



