Whoo! Your acromyrmex are pokey! The ones my ant friends (myrmecologists) keep in their lab are not so pokey as that. They just have our local sonoran desert species, whichever that one is. They are kind of difficult to keep around here; it's difficult to maintain the proper humidity in the fungus chamber. What does your set-up look like? I've got my seed-harvester colony (Messor pergandei) back in a CD case. I put them in a commercial ant farm frame, and they just hid at the bottom all the time--the one place you can't see them.