Notes from Underground say

         Notes from
                        Underground

The quest for Pogonomyrmex anzensis Cole

by

Gordon C. Snelling

      When William Creighton collected P. anzensis in 1952, little did he know the headaches his collection of this ant would create. Over the years since his first collection, many individuals have made the pilgrimage back to Split Mountain in an attempt to relocate the species. However all of these attempts were doomed to failure, the main reason for this failure was a lack of understanding of this ant. Creighton's notes indicate that P. anzensis was collected under a rock and the assumption was that this was in the wash or adjacent desert area. An assumption which would soon be proved incorrect.
     In early 1998, Stefan Cover, Robert Johnson and myself decided to once again take up the quest for this elusive species. Because the type locality is within the confines of Anza Borrego Desert State Park, appropriate permit arrangements had to be made, however as the park was at that time endeavoring to get a handle on the species diversity within the park, the permit was not a problem. Once we got accommodations sorted out with park personnel we began to plot our plan of "attack". Due to the late hour, only limited searching confined to the area immediately adjacent to our campsite was possible. As expected the early attempts were futile.
     The following morning we set out early, our goal was Split Mtn., the type locality for P. anzensis. Upon our arrival we split up and began to scour the wash bottom and lower hillsides adjacent to the wash bottom. Common in this area were P. californicus, D. bicolor and Myrmecocystus flaviceps, but there was nothing that appeared to be P. anzensis. So, time to think outside the box. Looking at the slopes around us we chose the less daunting west slope for our first attempt, A relatively short time of clambering around on this slope convinced us that the object of our quest probably was not there and led us to the conclusion that we needed to move on to the more rugged east slope.

This slope was well covered with large heavy rocks and was extremely steep; not your typical habitat for any Pogonomyrex, yet we had struck out in the more typical habitats, so up this hill we went. Several minutes were spent scouring the hillside then a shout went up, Stefan had found something, we all met up and examined his find, clearly a "Pogo", but it matched none of the others from this area. Finally we had found this enigmatic ant, however we were not done yet. We still needed to locate the colony. More time spent stumbling and staggering around on this slope led to several more foragers being located but no nest. Finally about mid morning a nest was located, as with everything else about this ant, the nest was atypical. Located next to a partially buried large stone, it consisted of just a single unmarked opening and virtually invisible chaff pile which was somewhat reminiscent of nests of P. apache, but was even more diffuse. Several other nests were finally located confirming that this was typical rather than an anomaly.

Pic of some bleak habitats looking down Hwy 2 in the Sierra Juarez in Mexico. The area in the foreground is very similar to the type locality of P. anzensis which probably also occurs here

      In addition to locating the ant one of our goals was to collect the unknown sexual castes, given the overall dryness of the surrounding soil, it was time for Bob to bring on his secret weapon... the 5 gallon jugs of water which he had lugged up the hill when we found the nest site. Once Bob had watered his chosen nest we decided to call it a day.
     On our way back to camp we decided to check another promising looking location in the Ocotillo Wells Recreational Vehicle area. No wasted searching this time, we immediately headed for the large rocky hill that dominated the area. Up the hill and within minutes we had located our quarry. Once again only scattered foragers were visible, however now that we thought we knew what we were looking for it was not long until we had found the nest. The nest structure was again the same at this location pretty much proving that this was the norm for this species. Since we had put in a full day already, we opted not to excavate anything here and just collected a few specimens knowing that tomorrow would be a rough one as we returned to excavate the watered colonies.
     The following morning we found that the water had done most of the job required of it, namely bringing ants closer to the surface and softened the soil so ask to make digging less the chore it would otherwise have been. Sadly though after excavating three colonies our major objective had not been met. No sexuals were to be found in any of the three nest looked at, but we did discover another anomaly. This Pogonomyrmex certainly has to qualify as the most inoffensive of any species in the genus. It is certainly less interested in colony defense than any of the species I have run across, Creighton in his notes mentions that the sting is "inconsequential" but says nothing more about it. I can certainly confirm that assessment, the sting of this ant is hardly worth noting. Of the several times I managed to force the ant to sting myself and several volunteers for the most part was there nothing more than a brief redness at the site which lasted a day or two, on no occasion was the actual sting even felt. The only exception to this was in 1999 on a return trip to the site; during the excavation process of another colony I received several stings in close proximity to each other on my lower arm. This stinging episode produced a swollen itchy site, which lasted for close to a week. I suspect this reaction was a result though of several stings so closely spaced and not a normal reaction.
     Justin Schmidt has done some preliminary work on the venom of this species based on material I sent him in 1998 and 1999 and has found a number of interesting things. But more work needs to be done before any real conclusions can be made.
     The return trip in 1999 was again in the hope of locating the sexuals, this time however there was success in the air. After about an hour of digging I located the first male in my excavation. Needless to say my thoughts of abandoning the dig fled my mind and I attacked the rocky ground with renewed vigor. Another hour or so of digging netted close to 100 males and females.
     There has been some thought that this species should be in it's own group, At first glance the sexuals do support this theory, however more study is needed before any definitive conclusion can be reached. There is no question that the sexuals are very distinctive and cannot readily be confused with any other species.
     We have since found two additional locations where this species may be found, however both samples are based on dead specimens scavenged out of spider webs under rocks. Since that last visit, conditions in the area have been so poor that there has been little ant activity of any kind. One location is well south of Park boundaries and presents a significant advantage since a permit is not needed to collect material. We are eager for conditions to improve so living specimens can be examined and venom results compared with the Borrego material.