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Bulletin American Museum of Natural Nistory. [Vol. XXIII, 



with clumps of canatilla (Ephedra), huge tree-like yuccas, and "allthorn" 

 bushes {KcchcrJinia) . In both localities the nests were surmounted by from 

 one to a dozen craters, varying from 10-30 cm. in diameter, and of very 

 elegant and regular structure (Figs. 16 and 17). This was noticeably the case 

 at Yucca, Avhere the craters were built of the coarse, uniform sand of the 

 arroyo bed. The earth or sand of the crater walls was often of a different 

 color from the surrounding surface, showing that it had been brought up 







p'i 



M '^ 





Fig. IS. Small crater of Alta (Mwllerius) versicolor covered with leaves of grease wood 

 {Covillma) collected by the ants at Tucson, Arizona. These leaves are also scattered along 

 the path leading to the crater (upper right hand corner of figure). (Photograph by the author.) 



from a considerable depth. The opening at the bottom of the crater was 

 2-3 cm. in diameter and was often closed with earth. Even about the open 

 craters no ants were to be seen during the intense heat of the day. Between 

 four and five o'clock in the afternoon, however, they were seen leaving the 

 ne.sts in files, and slowly moving towards some desert shrub in the neighbor- 

 hood for the purpose of cutting and carrying home its leaves. At Tucson 

 some of the colonies were collectino; the entire vouns and tender leaves of the 



