Pogonomyrmex – Page 3 – Wild About Ants

April 28, 2012

Identifying the Pogonomyrmex of Arizona: Terminology

When I introduced this topic last time, I realized that:

I didn’t define the terminology I was using, and
I used some outdated terms.

For example, I mentioned spines on the epinotum as a characteristic of some species of Pogonomyrmex. About half of you probably asked, “What is an epinotum?” and the other half said, “It is now called the propodeum.” Mea culpa.

In his work, Pogonomyrmex Harvester Ants: A Study of the Genus in North America, Arthur Cole uses “epinotum” to label the first abdominal segment in what is now called the mesosoma (the midsection of the ant). As Roberto Keller clarifies, the area is now called the propodeum. (See also David Louis Quinn’s discussion.)

Propodeum (in blue) armed with spines in an Acanthoponera minor worker (Scanning Electron Micrograph, Roberto Keller/AMNH)

To avoid further confusion, I’m going to develop a Pogonomyrmex glossary (and get myself into even deeper trouble).

Let’s start with:

Psammophore – the long hairs that form a basket shape on the under side of the ant’s head. Alex Wild has a fabulous post about psammophores.

I have to say although I realize there are excellent reasons for changing the names of both morphological characteristics and also species, it makes searching the older literature difficult. In these days of keywords reigning supreme, changing the keywords every few years results in loss of valuable information. Or maybe I’m just getting old 🙂

April 9, 2012April 10, 2012

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

January 8, 2012

Ants in Winter: Part 2 Pogonomyrmex in Arizona

In the last post, I looked at carpenter ants overwintering in upstate New York.

Here is Chandler, Arizona the temperatures the day this was taken ranged from a low of 45° F (7° C) to a high of 78° F (26° C). What are the ants doing here?