How can you tell? I'm curious, because according to the Catalog of Hymenoptera (Krombein et al 1979), P. maricopa "nests and habits are similar to those of P. californicus," whose nests "are surmounted by a circular or semicircular crater of loose sand and have a single entrance." I read somewhere else (I forget where) that californicus does not cut down vegetation. Based on the nest descriptions in the Catalog, I would have guessed these were P. barbatus: "The usual nest is a low to high gravel mound, frequently with a scooped-out crater, though the nest structure varies. The most conspicuous ant of this genus in its range."

Also, is it your sense that these mounds are entirely excavated material, or are they formed by denuding existing mounds of vegetation and adding some excavated material to the top?

Thanks for posting your image. I made a point of stopping to check those mounds out when I was passing through.

Not maricopa, I have never ever seen that species build mounds of that magnitude. I would be leaning more towards occidentalis or similar. A shot of the mandible would help to pin it down if you have one.

At the time I was working with William Mackay at UT El Paso and he has positively IDed these ants as P. maricopa. There are voucher specimens in both my personal collection as well as the collection at UTEP. They lack propodeal spines, have a straight anterior edge to their clypeus, and are larger and more strongly punctate in the intrarugal areas than P. californicus. This is the only area I've seen these massive mounds too. In empty lots in the city they usually only have small openings in sandy soil. I believe P. occidentalis has well developed propodeal spines as well as the offset basalmost tooth. It also does not occur in El Paso or any of the Southeast New Mexico counties. My main reference is "The Ants of New Mexico" by W. Mackay and E. Mackay 2002.

Paul thanks for the extra information I have now found reference to P. maricopa building large mounds. That and the information you have given does seem to point to this being the correct Ident for these ants. However I would not be shocked if somewhere down the road these turn out to be an undescribed but very similar species, as is happening to californicus in california.

Did that reference say they constructed mounds this big, like, assuming the whole thing is the work of ants?

Nothing to indicate the size being that large.

What's the reference you're looking at? Thanks

Ants of Nevada by the wheelers. Couldnt find my copy of Pogonomyrmex by Cole to check that one.

I know, its strange. We were all pretty amazed. Even in White sands NM they don't make mounds like this, although I guess they don't have access to gravel to stabalize it. But now that I'm thinking I've been back and forth across Fort Bliss as part of a different job and never saw anything similar out there, even in very similar sandy habitats. For a time there we went out and sampled a number of the nests to get reproductives and see if they were a different species. In addition to the large mounds they also were larger in body size than other P. maricopa we'd seen. However the work fell through and we never did any serious analysis. This nest is the largest we've found. The others usually had multiple crater like entrances and were half a meter tall and 2 or 3 meters in diameter. Ususally they would dominate a low spot between the coppice dunes. On warm days the ground would be covered with foraging workers. An interesting note is that although they cleared most vegetation from around the nest, they weren't able to stop this ground creeping plant that exuded a latexy fluid when broken. In summer this grows even on the mound. I'll try and dig up some other pictures.

I've added one very small shot and one very blurry one... these guys aren't too keen on holding still for a photo. Do these help at all?
(Did you get any shots of the ants, Noah?)

yeah, not so much...

I don't think the ants built those whole mounds. Going on my intution from the pictures and then from what I saw when I visited the site, it seems that most of the mounds around are part of a plant-stabilized wind driven shifting dune system. The ants seem to appropriate existing mounds and add a thinner cap of coarser sand on top. The large base of the mounds themselves are almost entirely fine grained sand that didn't seem to be sorted by ants, and none of the smaller ant mounds were made of the fine-grained sediments.