Identifying Pogonomyrmex in Arizona: Part 1

In his book Bees, Wasps, and Ants: The Indispensable Role of Hymenoptera in Gardens, Eric Grissell laments that ant species are difficult to tell apart, more difficult than other types of insects that he has worked with in any case. Most of the time, I would disagree. When it comes to telling apart the harvester ants of the genus Pogonomyrmex, however, I can definitely see his point.

I grew up in the East, so I had never seen Pogonomyrmex before moving to Arizona. That may be part of the problem.

Most pogos look very similar:  reddish brown.

They are all about the same size. Most have spines on the epinotum. They have rugae (ridges) all over the place. Let’s just say telling them apart is not black and white.

This year it has been my goal to learn the 14 species of Pogonomyrmex found in Arizona:

  • Pogonomyrmex anergismus
  • Pogonomyrmex apache
  • Pogonomyrmex barbatus
  • Pogonomyrmex bicolor
  • Pogonomyrmex californicus
  • Pogonomyrmex colei
  • Pogonomyrmex  desertorum
  • Pogonomyrmex  huachucanus
  • Pogonomyrmex  imberbiculus
  • Pogonomyrmex  magnacanthus
  • Pogonomyrmex  maricopa
  • Pogonomyrmex occidentalis
  • Pogonomyrmex pima
  • Pogonomyrmex rugosus

Today I’m going to start with one I can identify, Pogonomyrmex californicus.

This is a Pogonomyrmex californicus worker. Can you see the lovely golden hairs under the head that make up the psammophore? This species has a well-developed psammophore.

Our local Phoenix, Arizona-area P. californicus workers have a distinct black gaster, which isn’t true of the species elsewhere in its range.

I have noticed that the workers often run with their gaster held up, like this one.

Of the species found in Arizona, only P. bicolor is similar to P. californicus in color, but bicolor workers definitely have spines on the epinotum, whereas californicus workers lack them.

Only 13 more to go 🙂

If you are looking for information about harvester ants, Pogolumina is the go-to place for Pogonomyrmex

Sandmat and Ants: Pollination?

It is spring and the flowers are blooming in Arizona.

Do you recognize the plants? I believe they are smallseed sandmat, Chamaesyce polycarpa.

In any case, ants were all over them.

On the day I visited, Dorymyrmrex bicolor workers were everywhere. Getting a little closer…

I could see the front of the ant’s head was covered with pollen.

Two more workers, with equally yellow mandibles.

The Dorymyrmex workers were definitely visiting the flowers* (see below).

I also saw Pogonomyrmex californicus workers in the sandmat.

They weren’t visiting the “flowers,” though.

The Pogonomyrmex workers were searching under the plants. I saw a lot of gasters in the air. Perhaps they were searching for seeds? I also wondered if there were extrafloral nectaries under the leaves or on the stems that were attracting the ants.

Frankly, I wasn’t that familiar with these little plants, so I wasn’t sure where the nectaries were.

Upon investigation, it turns out that what look like *flowers* are actually special flowering structures unique to euphorbs called cyathia (singular cyathium). What look like anthers are actually male flowers and at the center is a female flower. The dark reddish areas near the center are the nectar glands within the cyathia. (For more details about the flowering structures see Wayne’s Word (scroll to absolute bottom of post) or the flower structure of euphorbs.)

In any case, it seems like this plant would be a great one to add to an ant garden. I’m looking forward to learning more about it’s life cycle and how ants interact with it.

What do you think?

Ant of the Week: Pogonomyrmex californicus

Pogonomyrmex californicus is a common harvester ant in the Sonoran Desert.


Ants of the genus Pogonomyrmex are generally easy to recognize by the presence of a psammophore, a series of long hairs resembling a beard on the underside of the head. In fact, the root of its name “pogono” means beard in Greek.

The species can be distinguished from others in the genus by the fact it lacks propodeal spines (spines on the back of the trunk). The color varies throughout the southwestern United States. BugGuide has a collection of photographs of Pogonomyrmex californicus, including some that look just like the ones shown here.


Like other harvester ants, the diet of Pogonomyrmex californicus consists mainly of seeds from nearby plants, although they will also scavenge dead arthropods. The seeds are processed and stored within the nest.

Unlike the fire ants, which forage in groups, the Pogonomyrmex californicus workers are often seen foraging singly, gaster held straight out behind.

Pogonomyrmex californicus is found in open areas, often in association with Dorymyrmex bicolor.

At least where human activity is high, the Dorymyrmex seem to predominate. See the dead harvester next to this mound?

Pogonomyrmex californicus queens may work together to form new nests, as shown in the video. Although some seem to be “working” together more than others. 🙂

Why do you think the one queen is vibrating her gaster? Is that why the other queens take off?

Obviously there are a lot of interesting things still left to be discovered about these ants.

For more information see:

Navajo Ant Project

List of North American Pogonomyrmex at ASU

Robert A. Johnson. (2004). Colony founding by pleometrosis in the semiclaustral seed-harvester ant Pogonomyrmex californicus (Hymenoptera: Formicidae). Animal Behaviour. 68(5): 1189-1200.

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Pogonomyrmex californicus Harvester Ants

While investigating the Dorymyrmex bicolor ants I posted about on Monday, I spotted a few other ants that looked similar, mostly because of their red-brown and black coloration.



On closer observation, however,  these ants were obviously another species. First of all, they were almost double the size.


The long hairs on the underside of their heads gave it away that these were harvester ants in the genus Pogonomyrmex. The ‘beard” of hairs, called a psammophore, is characteristic of the genus. In fact, the name Pogonomymrex means “bearded one.”  Psammo comes from the word for sand in Greek, so the psammophore acts like a basket or an extra pair of hands to help the ants move sand, dirt, and probably some types of food as well.


These turned out to be a color variant of Pogonomyrmex californicus. Cole (1968) describes the species as concolorous light ferrugineous red in coastal California, moving to concolorous black or brown to the eastern part of its range in southern Texas.

Ants of the Southwest has a good page about these harvester ants that shows some of the the color variations.

It seems that Dorymyrmex bicolor and Pogonomyrmex californicus are often found in the same open, arid environments. It’s interesting that at this Maricopa, AZ site their coloration is so similar.