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Article XXXI.— THE FUNGUS-GROWING ANTS OF NORTH 



AMERICA. 



By William Morton Wheeler. 



Plates XLIX-LIII. 



Introduction. 



Among the multitudinous activities of insects, none are more marvellous 

 than the fungus-growing and fungus-eating habits of the Attiine ants. Not 

 only are these habits of interest as a most unusual specialization in diet — 

 for all ants were originally and many are still exclusively entomophagous — 

 but the successful cultivation of such delicate plants as fungi presupposes 

 an astonishing range and complexity of adaptation even for these very 

 plastic insects. This statement will be endorsed by those who have tried 

 to obtain pure cultures of fungi either in the hot-house or the laboratory. 

 Besides the selection of proper culture media and the accurate regulation 

 of temperature and moisture, exquisite precautions have to be taken to 

 exclude the germs of alien species. The Attii are able to achieve all this and, 

 what is equally remarkable, at least two other groups of insects, namely, cer- 

 tain Old World termites and the "ambrosia beetles" (Tomicine ScoMidae) 

 of both hemispheres, have independently developed analogous habits. 



The fungus-growing ants all belong to a single Myrmicine tribe, the 

 Attii, and all the species of this tribe are fungus-growers. They are, more- 

 over, confined almost exclusively to tropical and subtropical America, only 

 a single species being known to range as far north as New Jersey. And 

 since a few others occur as far south as Argentina, we may say that the 

 geographical distribution of the tribe extends from 40° north to 40° south of 

 the equator. About one hundred species, subspecies and varieties of Attii 

 have been described and have been distributed among various genera and 

 subgenera, as follows : 



Genus Atta Fabricius. 



Subgenus Atta sensu stricto, including: A. cephalotes L. with the vars. 

 lutea Forel, opaca Forel, polita Emery and integrior Forel; sexdens L., with 

 the subsp. vollenweideri Forel; Icevigata F, Smith; columbica Gu^rin; 

 insularis Guerin; jervens Drury; texana Buckley. 



Subgenus Mccllerius Forel, including: M. heyeri Forel; striata Roger; 



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