94 Bulletin American Museum of Natural History. [Vol. XXII, 



that at this point the difficulties in the way of adoption become more 

 serious. There is unquestionably a pronounced antipathy among ants 

 to the formation of mixed colonies by consociation of adult individuals, 

 unless the insects themselves have exceptional characters or hap- 

 pen to be living under exceptional conditions. The female, on the 

 one hand, must have instincts that lead her to behave in a con- 

 ciliatory manner when she is surrounded by alien and hostile workers, 

 and in all probability also a peculiar neutral, agreeable, or, at any rate, 

 pacific odor. On the other hand no prosperous ant colony adopts fe- 

 males of alien species. They could be tolerated only by small, de- 

 pauperate or effete colonies which had lost their queen or queens and 

 were on the verge of extinction, or by incipient colonies under similar 

 untoward circumstances. Even under these conditions adoption may 

 be rare and exceptional, so that it may chance to occur only in the nests 

 of very abundant and widely distributed species like F. fusca and 

 pallide-fulva. But the good fortune of being able to found a colony 

 with the aid of alien workers, though so rare, may still be sufficiently 

 frequent to insure the survival of the species of the rufa and exsecta 

 groups, especially as these insects, when once established in a neigh- 

 borhood, are able to produce enormous and long-lived colonies. 



Miss Fielde ^ has recently published some observations and con- 

 clusions which would seem to contradict not only the views which I 

 have advanced in this and several other papers, but also those of 

 Forel and Wasmann. She sums up her experience in the following 

 sentences: "In no species of ant have I found workers that would 

 tolerate the presence of any queen of unfamiliar odor, nor any queen 

 that would willingly remain among workers of unfamiliar odor. Al- 

 though all species of ants have not been tested we may well assume 

 that what is shown to be a fundamental trait in a few species will man- 

 ifest itself in all species of the tribe." 



While I do not doubt the accuracy of Miss Fielde's observations I 

 am not prepared to accept her conclusions in the comprehensive and 

 somewhat schematic form in which they are stated, since they seem 

 to me to be subject to the following limitations: 



First, although simple at first sight. Miss Fielde's hypothesis be- 

 comes very complicated on closer scrutiny. If I understand her cor- 

 rectly she recognizes definite reactions to odors which differ with the 

 species (specific odors), a "nest aura," an odor of the trail, a female 

 and worker odor, that is, an odor which undergoes progressive change 

 during the life of each individual, at least in the workers (progressive 



1 The Progressive Odor of Ants. Biol. Bull. X, No. i, Dec, 1905, pp. 1-16. 



