1911] Wheeler — Two Fungus-Growing Ants from Arizona 97 



a vertical gallery descended into the soil but was followed only 

 a few inches to where it passed under a boulder that could have 

 been removed only with a charge of dynamite. The soil about 

 the nest was so hard that it had been soaked by a recent heavy 

 rain only to a depth of eighteen inches and the walls of the fungus 

 chamber were very dry and dusty. 



The colony inhabiting this nest was very large, comprising 

 several hundred workers and being fully four to six times as popu- 

 lous as the largest septentrionalis and turrifex colonies I have seen. 

 The workers were also more rapid in their movements and feigned 

 death much less readily than our other species of Trachymyrmex. 

 The colony was evidently in a hibernating or subdormant condi- 

 tion and contained neither larvse nor pupee. I also failed to find 

 any dealated queens, but these may have escaped into the lower- 

 most galleries as soon as the surface boulder was removed. The 

 breeding season of the species probably does not begin till just 

 after the rains in early July. This is indicated by the late appear- 

 ance of the males and winged females which were taken, evidently 

 while on their nuptial flight, by Schaeff'er, on August 24. 



All the other colonies of T. arizonensis found in the Huachuca 

 Mts. were examined less thoroughly, but all had essentially the 

 same structure at the surface of the soil. The entrances, usually 

 only one or two in number, were always near or just under the edge 

 of some large stone and when this was removed the galleries could 

 be followed along the surface for several inches before they de- 

 scended to a lower level. In two instances portions of the surface 

 galleries were packed with fungus-garden refuse in a manner that 

 recalled the conditions I have described for Cyphomyrmex wheeleri 

 {loco citato p. 768) . Unfortunately I was unable to reach any of the 

 chambers in these nests and was therefore unable to determine 

 whether the size and conditions described for the single nest 

 excavated with the aid of Mr. Palmerlee, were normal. I believe, 

 however, judging from the character of the soil in which these 

 ants live, that the chambers are commonly under stones and that 

 the fungus-gardens are suspended from the under surfaces of these 

 and not from rootlets as in the other species of Trachymrmex that 

 have been studied. 



On warm days the arizonensis workers may be seen about the 

 entrances of their nests. They go forth timidly and singly like 



