Continuing on a quest to learn to identify the Pogonomyrmex, I found a nest of the desert harvester ant, Pogonomyrmex desertorum.
Character number 1: They are a bit smaller than most harvesters, workers roughly 6mm in length.
According to Cole, the P. desertorum in the western regions have more ridges (rugae) on the head and pronotal area (mesosoma) than those farther east, but in general they have fine rugae and are quite shiny or have a “silky luster.” I would say they are pretty difficult to distinguish from Pogonomyrmex barbatus, although they do have finer rugae.
These had a simple nest opening, with none of the scattering of pebbles you see with many harvesters.
The workers were forging singly, apparently large on plant material.
According to Pogonomyrmex guru Pogolumina, Pogonomyrmex desertorum colonies are usually quite small, around 500 workers.
One claim to fame for desert harvester ants is that they are prey for horned lizards. As horned lizard numbers are on the decline, that might make these little guys pretty important.
According to Antweb, the 15 species of Pogonomyrmex in Arizona are:
- Pogonomyrmex anergismus
- Pogonomyrmex apache
- Pogonomyrmex barbatus
- Pogonomyrmex bicolor
- Pogonomyrmex californicus
- Pogonomyrmex (occidentalis-group) colei
- Pogonomyrmex desertorum
- Pogonomyrmex hoelldobleri
- Pogonomyrmex huachucanus
- Pogonomyrmex (Ephebomyrmex) imberbiculus
- Pogonomyrmex (californicus-group) magnacanthus
- Pogonomyrmex maricopa
- Pogonomyrmex occidentalis
- Pogonomyrmex pima
- Pogonomyrmex rugosus
I have a ways to go…