I now recognize these easily by their long legs, but still get their genus name confused with Acromyrmex. A human couple, on the trail with their dogs, paused and informed me that last summer they had seen a coral snake duck into this very nest entrance. Images taken with a Canon SX10 IS using "auto" mode and "macro" function. Time was late morning in a hilly saguaro-mesquite-paloverde habitat. An hour later there were no ants to be seen here.