1911] Wheeler — Tico Fungus-Growing Ants from Arizona 101 



may care to study the interesting fungi which they grow and eat, 

 I may add a few remarks on the two species which occur with 

 T. desertorum. These are Atta (Mcellerius) versicolor Pergande and 

 Cyphomyrmex rimosus Spinola. The former is very common and 

 conspicuous not only in the open deserts about Tucson, but also 

 at Yuma, Yucca and Benson, where I took it during the past 

 autumn and in Garden Canyon in the Huachuca Mts., where it 

 has been taken by Mr. W. M. Mann. Its workers are polymorphic 

 and those of the smallest caste are in size and coloration so much 

 like Trachymyrmex desertorum that this ant is very easily over- 

 looked even when one is scrutinizing the surface of the soil with the 

 closest attention. Cyphomyrmex rimosus, which, as I have shown 

 {loco citato p. 771), grows a very peculiar fungus on moist cater- 

 pillar excrement, nests in the shade of trees and bushes, and 

 although I have taken a few specimens along the banks of the dry 

 arroyo near the Desert Laboratory, I have found the species more 

 abundant on the damp walls of the irrigating ditches along the 

 Santa Cruz River between the laboratory and the city of Tucson. 

 Since C. rimosus is a very small ant, colored much like the soil 

 and quickly stops running or curls up and feigns death when the 

 soil in its vicinity is jarred, it readily escapes observation. Fortu- 

 nately its nests are shallow and its remarkable fungus-gardens, so 

 unlike those of the various species of Atta, Mycetosoritis, etc., 

 are easily unearthed and examined after they have once been 

 located by following homing workers. 



