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A Leafcutter Ant Adventure in the Lower Rio Grande Valley

- by A Sunjian
Atta texana
Atta texana worker cutting grass blade in Mission, Texas.

This is a narrative of a 4-day trip I took to Texas in search of Atta texana and the famed Atta mexicana. For more on the paper (A survey of Atta texana on the southern tip of Texas) that was published from this trip, click here.


It was with great anticipation that I stepped off the airport gate and walked into the somewhat humid air of Brownsville. The Brownsville airport, which boasted one gate and was so small that all the car rental agencies had been squeezed into one room - right next to the lone and lonely baggage carousel - was only steps away from the small lot that harbored the combined fleets of all rental companies.

I found the van that would be my constant companion for the next four days and eased into the driver's seat, throwing all my various ant collecting paraphernalia onto the passenger's seat. This included my camera, my Magellan eXplorist 100 GPS, and various collection vials. I also had my Nokia 9300 smartphone in my bag. I had installed the test version of DustyNotes Explorer into the mobile device two days earlier and I was raring to test it out in field conditions. I would be entering all my collection data into it, then using the export functions to create KML files for use in Google Earth. I wanted to upload the data immediately to Google maps, but that feature was not yet available for testing.

I took a deep breath before easing into the road leading to the main highway, the sensual female voice of my auto GPS counting down the distance to the next turn. I would be making full use of the auto GPS, especially as I had brought no hardcopy maps with me. It was exhilarating, the feeling that my trip was just beginning and that I had an entire future of anting ahead of me!

I have been anting sporadically for leafcutter ants since 2001, in such far-flung places as Mexico and Costa Rica, and so I had an idea what strategy to employ in my quest. In many ways, my strategy was somewhat counter-intuitive to what many people might think when imagining how naturalists foraged for their favorite critters. Although I would be spending quite a lot of time by myself wandering around urban landscapes and more natural areas in search of foraging ants and colony nest sites, I would also be socializing with quite a lot of people I meet on the way. Leafcutter ants tend to stop foraging during daylight hours when the days are hot and sunny, and due to the fact leaf cutter colonies are more scarce and widely scattered than the Pogonomyrmex harvesters and Solenopsis fire ants in this area, relying entirely on myself to spot and find these ants would mostly be futile, akin to finding needles in a very large haystack, especially considering the fact that I would only have 3 days to do my surveys. Instead, I would depend on the observations and experiences of the natives in the area, who had the benefit of years maintaining vigilance on their gardens and parks and sidewalks.

I decided that I would not head straight to my motel in McCallen, but that I would visit as many of the parks and towns in between Brownsville and my motel in search of Atta texana leafcutter colonies. I would be sticking to the World Birding sites on this first trip, and I decided to visit Harlingen's Arroyo Colorado.

When I got to the park entrance, which had various trails leading into the interior, I found that there was only one other car in the rather small parking lot. I changed into my hiking pants and boots and trudged into the paths. Alas, although I met an Amerindian guy who introduced me to some of the native wild plants (he bravely ate some of the very hot fruits from some pepper plants in the park, I found not one sign that any leafcutters were in the area. Lots of harvester ants, so much so that I could not believe people had been worried these ants were in danger of extinction from the fire ants.

After visiting a couple of other parks (including Estero llano grande state park in Weslaco), I decided to call it a day and checked into my motel, in the heart of McAllen.

Atta texana wingless queen bites me.
A surprise visit by a wingless Atta queen.

I took a shower and watched some TV for awhile. Imagine how flabbergasted I was when a huge female alate walked right in front of the TV! I thought at first it was a carpenter queen, but it was a leafcutter!

I scooped it up, noting that the queen was emitting a very distinctive vibrating sound. Much to my surprise, the queen ant was aggresive and started to bite me!

I went outside and managed to find two other queens, as well as numerous males. I guess luck favors the hard-working after all!


I resolved to visit Bentsen Lower Rio Grande State Park today, and early in the morning I got up and drove over to the relatively nearby park. I then spent the next few hours trudging the somewhat muddy grounds of the inner paths, vainly seeking some lone Atta texana forager along the darkened natural corridors. Surprisingly enough, my first encounter with leafcutter foragers occurred instead along the side of the main road, when I found the conical mounds of a small nest situated quite close to some picnic grounds. I guess there's some sort of lesson to that, on the order of "What you seek will always be where you least expect it".

The interesting point I guess from a research perspective is that this seems to support the notion that Atta leafcutters are critters who like relatively open spaces, which could explain why they do very well indeed when human beings come in and cut down trees and forests in order to build their relatively open suburbs and towns.

I then found several other Atta nests, all near the open spaces along the road, and I proceeded to measure the nests and take some samples. Atta texana is a somewhat drab ant, and even the large soldier cannot be said to be as interesting looking as Atta mexicana soldiers, with their massive shiny heads. Nevertheless, I was quite happy, and took the time to call my wife on my cell and see how she was doing. Ah, the wonders of modern technology, when everyone is only a few button presses away even when you're in the middle of a large park anting!

I later discovered some gigantic leafcutter nests that were only several meters inside the forest edge along the main roadway. The nests were huge mounds of soil that seemed to swallow the lower trunks of the surrounding trees (see image below), gigantic structures that I never saw before even in Mexico. After taking some Atta texana worker samples and suffering through the very muddy soil in the undergrowth, I left the park and had some lunch. I wanted to drive around the surrounding towns as well to see what I could find.

A HUGE nest of Atta texana along the side of the main pathway heading into Bentsen Park.
A HUGE nest of Atta texana along the side of the main pathway heading into Bentsen Park. The nest is somewhat hidden by the foliage along the side of the road.

The interesting thing is that quite a few people I met during this afternoon suburban exploration knew about the leafcutters, and I soon ended up in a church. I had been told by a friendly townsperson that his brother had been trying to kill a large colony of leafcutters in the church. I spoke to one groundskeeper, who excitedly directed me to the nest under a tree, and told me that they had repeatedly tried to fumigate and kill the colony but had failed spectacularly. Indeed, the nest was composed of a large number of mounds that spread in a circular pattern under the luckless tree, and large numbers of leafcutters (Atta texana) rushed to and fro in their usual manner.

Atta texana distribution in texas Lower Rio Grande.
A church yard in Sunjian had a medium sized nest on the front yard, which proved impossible to kill even with fumigation.

As the afternoon wore on, I decided to return to Bentsen park, where I met the very friendly and hospitable Dr. Joshua Rose, the area's resident insect expert, as he prepared for the park's nightly excursion. He showed me some other Atta texana nests, all again in the relatively open spaces close to the road, and educated me on some of the subtleties of park maintenance. By this time, the mosquitoes were starting to be a real bother, and I finally left for the motel back in McAllen.

It had been a pretty full day, but one which was also very productive.


I resolved to go to Falcon State Park today, but because I knew it would take an hour or more to get there, I decided to take my time and visit all the small towns in between McAllen and Roma, near where Falcon State Park was located.

I spent some time at Rio Grande City, where the negative responses of all the people I talked to threatened to cast a pall on my search, before I met an old retired rancher who immediately said that he had indeed seen these ants climbing and defoliating a tree in his yard. He regaled me with stories about the dangerous border area, which turned out to be just a few hundred meters away, and we were soon joined by his wife.

As I passed through the busy Roma downtown, I suddenly spotted the large sprawling nest mounds of a large Atta colony situated to one side of a park close to a Starr Bank, and right across from the modern Riverview Mall.

At Falcon State Park, I spent the entire afternoon going through the trails. It was a very hot day, and the harsh sun burnt through the sunblock I had lavishly applied upon my exposed arms, face, and neck. The vegetation here was of the semi-arid variety, including various cacti.

I spotted the carcass of an Atta alate, where it lay, disarticulated, as if impaled upon the thorns of a drying cactus leaf, but was totally unsuccessful in finding any Atta nest holes or foraging workers.

Atta texana impaled on cactus thorns.
The disarticulated remains of what I take to be an Atta texana alate litters the surface of a rotting cactus stem.

On the way out I talked to the female ranger, who told me that she had these leafcutters in her home, and that she had tried to get rid of them earlier but had failed. I implored her to take a sample for me, which she readily acquiesed to, such is the kind heart of these men and women who take care of the national and state parks.


I woke up this morning by 830 am, certainly much later than I usually do. I decided I would not hurry today. I put in some gas at the Heb's, then off to Falcon State Park, and this time I did not need the GPS to point out where route 83 was located, as I have become almost a native in my knowledge of this area. I'm off to see what the kind ranger had gotten for me, although I did not hold much hope for it being Atta mexicana, given the fact I had found that very large colony of Atta texana in the middle of Roma yesterday.

The drive was uneventful, and I listened in true leisurely fashion to my Book on Tape, The Last Juror, by John Grisham, who always tells a good tale. When I got to the entrance of the park, the ranger who gave me my ticket was a man, but the woman I talked to yesterday was in back, and seeing me, hurriedly passed along her sample, apologizing that she only saw the smaller ants. I said everything was ok, and parked the van and chatted with them for a few minutes. The other ranger also noted that he had seen the same kind of ants in his in-law's home.

Atta texana with seed in Bentsen Park Texas.
Atta texana worker in Bentsen Park prepares to carry a large seed.

I decided that I would go only to those places that I did not visit yesterday, and ended up in the first picnic area, one that was close to the reservoir. I wandered over close to the waters, noting the tall grasses and sandy nature of the soil, then headed towards the area with more desert vegetation. As I crossed from the parking lot asphalt to the thorny growths, imagine my surprise when, a scant 4 meters or so beyond the boundary I saw what looked to be an Atta nest underneath the thin leaves of some grass. Peering down I immediately determined that they were Atta, and after securing a single sample and recording all the notable details, tried to locate the other nest holes, something which was easier said than done, as the very thorny leaves and branches of the plants in the plot of land continuously threatened to impale me. After 10 minutes of fruitlessly searching for the main nest, I walked back to the picnic grounds, walked quickly farther along, then again plunge into the maelstrom of vegetation after seeing a semi-path open before me.

Incredibly, this time I found several larger nests located beneath the shade of a flowering tree. As in the first nest hole, the Atta were exiting the nest holes in lines as they dumped soil into the ever-growing pile that encircled one side of the nest holes.

I was now facing a quandary. Should I continue to explore the surrounding area to find more nests, or continue on my way to Laredo in hopes of finding Atta mexicana there, before returning to the park on the way home when I can catch the ants out in full force as the day cooled?

I decided that I would chance the trip to Laredo, since I knew Falcon State Park would remain open until 10 pm. I had a large flashlight with me, and I determined that I would not be deterred by thoughts of drug smugglers, or the border patrol, finding me crawling around in the dense undergrowth.

Atta texana with berry in Falcon State Park.
Atta texana worker in Falcon State Park carries a large berry.

So I headed west, and the already-scarce evidence of civilization gave way to vast fields and ranches as I chewed the distance to Laredo. I was glad I had brought along the Book on Tape, but I was also worried that I was just as quickly going through the CDs and might have nothing to sustain me on the way back.

I hit the town of Zapata. The empty fields of oranges suddenly gave way to houses and McDonalds, Subways, and Pizza Huts. Curious about the possibility of finding what I was looking for in this very hot and isolated town, I started nosing around the various public buildings I could find, beginning with the town courthouse and finally ending up in the local hardware store, where a rather pretty clerk laughingly hinted that she had seen these hormigas arrieras carting off tortillas! One older woman though mentioned that she had them in her house, and she described the large multi-nest architecture that Atta so favored. Unfortunately, I felt awkward trying to ask her if I could tag along to her house, there and then, in front of all these people, so I ended up giving up on that line of search and continuing on my way.

Which ended with me hitting the Zapata public library and asking the librarians about leafcutters. Like almost all librarians everywhere, these women were very kind and helpful people, who even took me out into their library yard in search of these ants. Amazingly enough, one of the librarians noted that she had these types of ants in her home, that they had defoliated her rose bush, and that they only came out at night, all of which got my hopes up that she indeed had leafcutter ants.

I took the plunge and asked whether I could come over to her home and take pics of the ants, as well as samples. To alleviate any doubts, I presented her with my driver's license and information about my website and my email.

Unfortunately, she could not get out until 5 pm, when the library closed, so I wiled away the couple of hours until then fruitlessly wandering around the birding park right next to the library, and such was the heat that this was not a minor undertaking. I took a break and got some drink at a nearby grocery store (a Super S) at the intersection of 9th avenue and Hwy 83. The last hour I spent tapping away at my mac in the library, before wandering the aisles perusing the rather limited number of books that were shelved neatly in tall wooden cabinets.

Finally, 5 pm arrived, and I followed this good librarian to her home, which turned out to be fairly close by. Unfortunately, the ants in her yard were Pogos! My hopes were dashed, and I explained that these ants were not the leafcutters. She insisted that these were the ants that she had described earlier, and the only explanation that I can come up with, other than crediting the harvesters with some nascent leafcutting tendencies, is that the ability of leafcutters to create extremely long foraging lines had somehow caused this good woman to confuse them with the harvesters. Perhaps the leafcutters had their nest mounds a hundred meters away, and multiple foraging lines had converged one night upon the hapless rose bush.

I apologized for taking her time, and she apologized in turn for the fact that the red ants she had in mind were not leafcutter ants, and we parted after I gave her an ethanol-filled vial and asked her if she could send me some samples later if she did manage to find some lof these ants.

At this point I could have given up and hurriedly made my way back to Falcon State Park. But my stubborn disposition came to the fore and I continued to drive around , somewhat aimlessly in the small streets of this very small town.

I came upon a day care center for the elderly , and wandered in, where a worker called a male nurse , probably because he spoke english, after I told her that I had some questions. Intriguingly enough, the man immediately said that he had these ants in his home after I had briefly explained my search, and he asked whether I could get rid of them. I said probably not, but that I could certainly reimburse him for any time he spent showing me the colony.

It seemed that today was my day for waiting, because I had to wait another 30 minutes for him to finish his shift, and so back to the Super S fI drove – the heat was intense, and I needed all the liquid I could get. Afterwards, we passed the time talking about how to get rid of the leafcutter ants in his home. My impression was that here indeed was a man who was desperate to rid himself of some major pest.

His concern was understandable when I saw the extent and size of the colony that infested the yard around his home. The front lawn was composed of tall healthy green grass, except for a four meter diameter circle near the front yard, where the grass seemed to have been clipped short, and from the center of this circle several nest mounds erupted like little brown hills. The owner gestured angrily at the lawn and said that the ants had been cutting the grass and keeping it short around their nests. He ushered me around the periphery of his home, and on all sides nest mounds poked their heads above the ground. This colony was literally encircling the entire house!

One of the things he pointed out to me was a large 20 cm hole that gaped from the ground like an open sore. The hole was blocked with soil about 10 cm down, but he assured me this used to be a large mound that washed away when the rains came, leaving behind a huge tunnel that he said had angled down and towards the underside of the house before being covered up by the ants.

He introduced me to a friendly looking gaunt man, who proudly showed me the latest chemical that they had been using against their tormentors. On the side of the can was a label that clearly stated it was a “Fire Ant Poison”, which explained why it had not controlled the leafcutter ants, who had withstood two previous chemical attacks as well.

On another side, of the house, he pointed a small tree that had half of its leaves to one side completely stripped away. At the base of the tree was another hole, this one about half the size of the previous one, but in this case there was lots of activity occurring around it. Cut leaf pieces littered the ground, and Atta texana workers and some soldiers were hurriedly running to and fro among the scattered pieces and dragging leaves into a nearby mound.

Atta texana nest with fire ant poison.
A desperate homeowner uses fire ant poison on one of the nest holes in his home.

At this point the guy who was seemed to function as my host's jack-of-all-trades came back with the fire ant poison that he had shown to me earlier. They dusted the white powder onto the large nest opening, which I saw did not faze the ants a bit. The leafcutter ants continued to go over, around, and through the faintly pathetic white powder.

I continued to take pictures and samples, and parted after exchanging emails with the homeowner, who was now worried that the large nest might affect the foundation of his home. I had promised my host that I would send him information about how to control the leafcutter ants.


Much as I would have loved to extend my stay for a few more days, perhaps travel to Laredo and the nearby border towns in Mexico, the time to end my journey had arrived. However, I resolved not to go down without a fight, and I packed up and checked out of the motel, the La Copa Inn, by 630 am, knowing that the trip to Brownsville would last one hour, and that this would therefore give me some time to explore Brownsville. Before my noontime flight back to Houston, and then to New Jersey.

I used the same techniques in Brownsville that I had used earlier, patrolling the streets in search of large mound-like structures, stopping and talking to any pedestrian whom I thought would have some idea about my quarry, and visiting the local park. Alas, these were all to no avail. The closest I came to any hint of success was when a gardener mentioned that his home had the kind of ant that I described a few years back. However, two other people evinced great interest in my quest, including a baptist minister who invited me to stay for the church services later in the morning!

I reluctantly checked into the airport at around 9:30 am. Although my flight was not until 12:16 pm, I had planned to check in early in order to make sure that I had enough time to get all my specimens in through the security checkpoint. The nation was in the grip of the never-ending terrorist wars at this time, and did not allow any liquids into carry-on luggage. This produced a quandary for me, as I did not want to place the ethanol vials with my check-in luggage – an overzealous workers could so easily throw them away, thus negating all the long hours I had spent collecting these precious specimens. I drained most of the ethanol from each vial, taking care not to lose the smaller ant samples, then repackaged the lot into my backpack.

(to be continued?)

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