In my prairie sites where I study the Comanche harvester ant, I have found two species of Trachymyrmex: T. septentrionalis and T. turrifex. I have 14 prairie sites and of these 8 have both species, 5 have only T. turrifex and one has only T. septentrionalis. Finding both species is quite exciting for two reasons: first, these are funky looking ants with all kinds of spiny projections on their bodies. So, they were one of the first ant genera I learned to identify correctly. And they are very cute. But the more exciting thing has been the discovery of the nests of T. turrifex, which are turrets. They have a bit of a crater area in the middle of which is this turret, about 2 and ½ inches long. I was quite astonished when I happened upon some of these structures and more so when I saw ants coming in and out of them. I got some photos and some video as well.
The nest of T. septentrionalis is very different. The entrance is a few centimeters from a characteristic crescent shaped pile of soil which they make as they excavate their nest.
These differences in nest form, and ant nest architecture in general, are quite interesting to me. I have no idea what the differences in form between these two Trachymyrmex species are about — they are living in the same kinds of habitats and I believe have similar life patterns, etc. So, these nest differences are quite a mystery.
Earlier this summer, I found some Solenopsis xyloni easily coming and going in and out of a T. septentrionalis nest. The S. xyloni, a native fire ant species, and T. septentrionalis met each other at the entrance to the Trachymyrmex nest without out any sign of aggression and the S. xyloni preceded to enter the nest. Trachymyrmex expert Dr. Jon Seal (University of Texas-Tyler) has observed the same but does not know what is going on.
Trachymyrmex ants are related to the leaf cutter ants in the genera Atta and Acromyrmex. Though technically, not leaf cutter ants, Trachymyrmex ants may collect leaves to grow fungus like the true leaf cutter ants. But my understanding from Jon Seal is that Trachymyrmex ants are not obligate fungus eaters. They forage on other foods as well.