As I was walking along Arizona's Rock Creek, near the Barnhardt Trail in the Mazatzal Mountains, I was looking under rocks for whatever goodies may be lurking. The altitude was about 5000', and the surrounding vegetation was a mixture of sycamore, ash and alder, surrounded by pinyon-juniper and oak outside of the riparian corridor.

Under one of the rocks, I found strange ants 5-6 millimeters long that were covered in turbercles. The ants were not very active, slowly walking around. They did not offer to bite or sting - indeed, some of them played dead. The nest was made out of a material that looked like dried mud. I did not see an entrance to the nest - no obvious cone or mound.

The ants were members of the genus Trachymyrmex. Like Acromyrmex versicolor, these ants take pieces of vegetation into their nests and grow fungus upon the vegetation. The ants then eat the fungus. Since this time, I've also found Trachymyrmex in the Whetstone Mountains, in Southern Arizona. Those nests usually had a "volcano" style cone associated with them.

A strange thing happened when I took some of the ants home for identification. Some - not all! - of the ants developed a white bloom on their exoskeletons. The bloom had a crystalline appearance, as though salt water had dried upon them. Not all of the ants within the sample exhibited this, and I did not notice it upon the ants when I collected them. According to Creighton (1950), prior to his revision of the genus this "bloom" was used as a character when keying out Trachymyrmex species. It seems he was correct in discounting it, since these ants came from the same nest!

Here is a Trachymyrmex worker walking over a portion of the nest material. The workers did not run, but walked very slowly. They made no offer to sting or bite.	Many of the workers played dead - they revived after a bit. This pair are on fragments of nest material.	A worker walking along the nest rock.
	Here is a close up of a preserved specimen. The small divisions on the ruler are millimeters. Note the slight whitish "bloom".	A head-on view of Trachymyrmex.
As the specimen with the bloom dried off, the bloom looked increasingly like dried on salts.	Here is a head on view of one of the workers which did not have the bloom.	And another head-on view. This is nice view of the various tubercles and protruberances with which the ants were covered.
Trachymyrmex in Arizona's Whetstone Mountains. This is a rear view at the nest entrance, showing the ant's abdomen.	Trachymyrmex removing excavated soil from the nest. This colony in the Whetstone Mountains had a "volcano" style nest mound.	Trachymyrmex emerging from nest
Pair of Trachymyrmex	More Trachymyrmex at the nest entrance.	A shot of a Trachymyrmex nest in Arizona's Whetstone Mountains (yellow arrow)

---

Home

---