Pogonomyrmex desertorum
One summer in July I went walking in the desert near Tucson. We were in our summer monsoons, so it had rained a couple of days previously. The clay-filled soil was drying out, and the ground was turning back into its "concrete like" state. I noticed a few ants excavating a nest.

They looked quite a bit like Pogonomyrmex harvester ants of some kind - specifically, they looked a lot like Pogonomyrmex barbatus, the Red Harvester Ant. But they didn't act like P. barbatus. These ants had a more silky appearance, and they were not nearly as defensive. I was able to sit next to the nest for quite awhile and the ants more or less ignored me...something that probably wouldn't happen with a P. barbatus nest. These ants were another type of Pogonomyrmex - Pogonomyrmex desertorum.

I watched them forage for seeds for awhile. They didn't go out in a stream, like P. barbatus, but rather went out in ones and twos. I was quite surprised to see them going to Pheidole xerophila nests. Pheidole xerophila is primarily a seed eating ant as well. These Pheidole are a fraction of the size of the Pogo workers. The Pogos were rummaging around in the soil near the Pheidole nest until they found a seed, then carrying it back to their own nest. When a Pheidole worker would encounter a Pogo, the Pheidole worker would clamber over the Pogo, biting at it.


  

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Pogonomyrmex desertorum worker. These ants seemed to become much more common around the time of the summer monsoon rains in Tucson. You can see that this one has dried clay on her petiole (the thin 'waist' of the ant)
Pogonomyrmex desertorum worker. These ants seemed to become much more common around the time of the summer monsoon rains in Tucson. You can see that this one has dried clay on her petiole (the thin 'waist' of the ant)
In spite of how inoffensive Pogonomyrmex desertorum usually is, when there is a mating flight of another ant species, they definitely take advantage of the situation. Here a P. desertorum worker is bringing a piece of a male leafcutter ant back to the nest.
In spite of how inoffensive Pogonomyrmex desertorum usually is, when there is a mating flight of another ant species, they definitely take advantage of the situation. Here a P. desertorum worker is bringing a piece of a male leafcutter ant back to the nest.
Pogonomyrmex desertorum seems to spend a lot of time rummaging around the nests of other seed harvestering ants. Here a group of Pogonomyrmex desertorum workers can be seen looking for seeds around a Pheidole xerophila nest, while the smaller P. xerophila minor workers cluster around their nest entrance.
Pogonomyrmex desertorum seems to spend a lot of time rummaging around the nests of other seed harvestering ants. Here a group of Pogonomyrmex desertorum workers can be seen looking for seeds around a Pheidole xerophila nest, while the smaller P. xerophila minor workers cluster around their nest entrance.
The Pogonomyrmex desertorum workers sometimes get quite aggressive about scavenging seeds. Here a P. desertorum worker is investigating the Pheidole xerophila nest entrance.
The Pogonomyrmex desertorum workers sometimes get quite aggressive about scavenging seeds. Here a P. desertorum worker is investigating the Pheidole xerophila nest entrance.
Pogonomyrmex desertorum worker grooming herself.
Pogonomyrmex desertorum worker grooming herself.
Pogonomyrmex desertorum worker scavenging seeds outside of a Pheidole xerophila nest. You can see a Pheidole xerophila minor worker crawling over the Pogonomyrmex's head.
Pogonomyrmex desertorum worker scavenging seeds outside of a Pheidole xerophila nest. You can see a Pheidole xerophila minor worker crawling over the Pogonomyrmex's head.
Pogonomyrmex desertorum worker looking for seeds. They seem to often take on this 'hunched over' posture.
Pogonomyrmex desertorum worker looking for seeds. They seem to often take on this 'hunched over' posture.
Pogonomyrmex desertorum worker scavenging around a Pheidole xerophila nest. You can see that the P. xerophila minor workers are taking exception to this, biting at the Pogonomyrmex.
Pogonomyrmex desertorum worker scavenging around a Pheidole xerophila nest. You can see that the P. xerophila minor workers are taking exception to this, biting at the Pogonomyrmex.
Pogonomyrmex desertorum worker emerging from her nest.
Pogonomyrmex desertorum worker emerging from her nest.