Rover Ants (Brachymyrmex patagonicus), an emerging pest species

As if we didn't already have enough pest ants to worry about, here is a relatively new one. The rover ant Brachymyrmex patagonicus, a tiny South American species, has been working its way under the radar across the southern United States. Its presence is now large enough that pest control companies are reporting a sudden increase in requests. According to gardeners I've talked to, these ants emerged in huge numbers here in Tucson about 5 years ago. Given the interest in this species, I thought I'd post a summary of what we know of this emerging pest and how to reliably identify it.

Distribution in North America. The map below is adapted from MacGown et al (2007), with additional data on the southwestern cities taken from my own collections, credible rumors from pest control folks, and from Dale Ward's Ants of the Southwest. Brachymyrmex patagonicus appears to be spreading in the southeast and has recently arrived in various western cities. I would not be surprised if it is already established in San Diego and Los Angeles. If you have seen this ant in a location not indicated below, please drop a comment or send me an email.

Biology. We do not know much about this species. Colonies nest in soil and leaf litter, often under covering objects such as stones. They tend hemipterous insects for honeydew and visit nectaries. In Tucson, mating flights occur year round, even in mid-winter on warmer nights. Alates are attracted to lights, generally appearing shortly after dusk, and their reproductive output is impressive. I've been running blacklights in urban Tucson for a couple of years, and B. patagonicus alates consistently outnumber those of all other ant species combined. Here is a mating pair:

The ecological effects of the Brachymyrmex invasion remain largely unstudied. (If you're an aspiring myrmecologist looking for a thesis project, this one's ripe for the picking!) The subjective consensus of myrmecologists is that B. patagonicus won't become a major pest in the way that, say, fire ants and Argentine ants are, but they do enter houses and might be regarded as a small nuisance for homeowners. In Tucson, B. patagonicus co-exists with native Solenopsis, Pheidole, Dorymyrmex, Camponotus, Forelius, and Pogonomyrmex without any obvious effect. On the negative side, they appear to have displaced a native Monomorium in my yard, but that is a single observation and is purely anecdotal.

Identification. All Brachymyrmex species have only nine antennal segments in the worker caste, reduced from the 11-12 segments typical of most other ant genera. This trait makes identification to genus relatively simple with sufficient magnification. That, and the fact that Brachymyrmex are really small. Few species break 3mm in length, and B. patagonicus is usually between 1 and 2mm.

To confirm that an ant is Brachymyrmex patagonicus, look for this combination of characters:

  • Eyes relatively large
  • Several long erect hairs present on the mesosoma
  • Body usually medium to dark brown in color
  • Appressed hairs on the abdominal tergites relatively sparse, so that the integument appears smooth and shining

For comparison, here is a photo of Brachymyrmex obscurior, a similar species that is also introduced from the tropics. Notice the smaller eyes and the denser covering of appressed hairs on the gaster:

Another commonly encountered Brachymyrmex in North America is the native species B. depilis. Notice the small eyes, the light color, the lack of standing hairs, and the dense covering of appressed hairs on the gaster:

One final nomenclatural note. Brachymyrmex patagonicus in the U.S. has sometimes been referred to as "B. musculus" based on an earlier misidentification. However, Argentine Brachymyrmex expert Estela Quirán recently confirmed the match between South American B. patagonicus and the North American populations, so the taxonomy of this new invader appears stable for now.


MacGown, J.A., Hill, J.G., Deyrup, M.A. 2007. Brachymyrmex patagonicus (Hymenoptera: Formicidae), an emerging pest species in the southeastern United States. Florida Entomologist: Vol. 90, No. 3 pp. 457â464.

Quiran, E.M., J.J. Martinez, Bachmann, A.O. 2004. The Neotropical genus Brachymyrmex Mayr, 1868 (Hymenoptera: Formicidae) in Argentina. Redescription of the type species, B. patagonicus Mayr, 1868; B. bruchi Forel, 1912; and B. oculatus santschi, 1919. Acta Zoologica Mexicana 20: 273-285.

Mississippi pest control extension sheet on B. patagonicus.

Joe MacGown's in-depth page on B. patagonicus

Specimen images from Antweb and from Joe MacGown.

More like this

My exterminator is calling the ants I'm having problems with "rover" ants. I live in Denton County, Texas (near Dallas). I would love to get rid of them - can you tell me what is effective? I found them in my child's bed the other day and that's the last straw.

I took some pictures (not very detailed) but I think they look a lot like that top picture (if those are the rovers). They look black to me but your lower pictures look more brownish. Here's my pics:

Anyway, I'm not in the red areas on your map. And I'm desperate to get rid of them.

Thank you.

Hi Susan. Your photos sure look like rover ants to me.

I wish I could give advice for getting rid of them, but as far as I know, no one has yet figured out a reliable way to do that. They're persistent little guys.

Thanks for your reply. Persistent is a good word for them. I sprayed some Raid Ant Killer in the bedroom (which I hated to do) and didn't let the children sleep in there for 2 days. So far I've not seen more in there but it's not even been a week.

When I had them in the kitchen, the exterminator finally had to put something inside the walls to knock them back. I am about convinced they were living in the walls (my kitchen has all interior walls) and no exterior treatment helped at all.

Thanks again for taking the time to look and reply.


Brachymyrmex patagonicus, also called the "dark rover ant", does occur in Denton, Texas. I collected specimens of this ant two weeks ago at a gas station on I-35 in Denton.

I live and work in Houston where this ant has become the number one pest species that pest control companies encounter. Complete control of this ant has proven challenging. They are very mobile and appear to move nesting sites with little provocation. Dark rover ants are primarily an outdoor species and this is where most efforts at control should be focused. However, outdoor perimeter treatment must be extremely through. Unfortunately, this is not as easy as it sounds and is not the norm for many pest control service companies.

Interestingly, ten years ago this ant was not even on the pest radar in and around Houston. While it could be collected easily outdoors it was rarely if ever encountered indoors. Ten years's everywhere, in huge numbers and defying most efforts to control it's abundance. Good luck!

Just received a call today from Texas A&M University that a sample I had submitted is confirmed as rover ants. I collected the specimen at a daycare in Beckville, Texas in Panola County.

I had sent them into A&M as they behaved similarly to the "Rasberry" ants being featured on the newscasts over the last several weeks.

I identified a rover ant infestation at Austin when our Veronica Obregon, from Communication's collected few from her yard.

You take great pictures and point out key taxonomic features of the species. Keep up the good work.

I have had tiny little black ants show up in my master bath and my office. I'll see about 6 to 10 in one day and then nothing for several days and then another cluster here and there. They don't seem to be "after" any item in the house and are really just there to annoy me since I pay for regular extermination. I called my exterminator who is coming out to "handle" them and he called them Floridian Rover Ants. He explained how persistent they are and what a pain they are to control and that they are sensitive to pesticides. If they detect pesticide in the area they simply back off for awhile and then come right back later or it drives them deeper into the house for protection. He said the key is to offer them a palatable bait that they will take with them to the colony.

Forgot to mention, I'm in Spring, TX, a northern "suburb" of Houston.

Not to sound like a solicitor for any certain product, but rover ants have become a serious problem in my area also. As a certified Pest Management Technician, I can tell you the most effective way to rid yourself of this problem. Tell your Pest Technician the best way that my company has found to deal with "rovers" is a product called 'INTICE THIQUID'. I am in no way affiliated with 'INTICE', but I can tell you from experience, that this product is by far the best bait for "rovers". A few drops in the pheremone path will draw them out in droves. They will then feed the larvae and destroy the nest.

By Anthony "The B… (not verified) on 07 Aug 2008 #permalink

WOW... I am very impressed with the photos.

amazing detail. and excellent macro shots.

thank you for the excellent work!!!!!!!!!!!!!!

By joe ( anther b… (not verified) on 09 Aug 2008 #permalink

Anthony, are you in Texas? I might hire you if you are near the DFW area. I just fired the company I've used for several years. Is that INTICE product used indoors, outdoors or both? Do you put it in a bait station? I am glad I bookmarked this post and came back to check!

I'm in Flower Mound, TX (DFW area) and we are having issues with rover ants in our master bathroom. So far they have kept themselves near the sinks. The Terminix guy came out a week ago and sprayed inside and out. They were gone for a day and then resurfaced. He came back out today to bait the inside of the bathroom. He couldn't do the outside since we are finally getting much needed rain. He used gel bait and bait stations. When he put them down there were about 20 or so ants on one side of the sink. I looked in there a few hours later and the amount had tripled and continues to grow every hour. At least they are taking the bait. Here's hoping it works!

I've noticed their "entry" points seem to be behind our mirror and one of the electrical sockets. That kind of worries me.

Glad I've found this posting as well. Judging by history and my naked eye I believe we have Rover ants in our master bath as well. Unfortunately the little buggers have been coming out of just about every possible opening in my walls and I've even found a few in other rooms now.

I'm in the Austin area as well and I'll be calling some exterminators tomorrow with specific questions.

In in NW Austin (Avery Ranch), and we have ongoing problems with these critters. Persistant is not strong enough to describe them. One thing I have observed is they love toothpaste and mouthwash. If they come out with an effective pesticide for rovers, mix it in with some toothpaste and they'll go nuts over it.

The bathrooms are their favorite hangouts. The kitchen not so much, which is weird because of the crumbs from the kids.

Anthony, thanks for the tip, I will pass it on to my pest service.

By Glen Colby (not verified) on 15 Sep 2008 #permalink

I live in Plantation, FL just west of Ft. Lauderdale and I can tell you that I am going crazy with tiny ants, hundreds of them, in my pool, expecially after it rains. They just cover the entire top of my pool. I have found out from Broward Extension Service, a part of University of Florida, that they are Rover Ants and there is nothing that will get rid of them. I can't belive that. I will ask my exterminator about Intice Thiquid. Thanks for the input.

Susan, If you are still having no success please contact ABC Pest & Lawn Service, Lewisville. We have been encountering the rover ants for the past several years and have had better than average success with treating them. Much like everyone is saying they are persistANT. They have multiple colonies and can nest almost anywhere.

We have been seeing these in south central Texas, Comal and Bexar counties.

By Patrick O. (not verified) on 12 Mar 2009 #permalink

I am in Bexar County (central San Antonio). We parked our car at the airport for four days and when we got home we noticed a few ants. The next day we noticed many more. They seem to be multiplying exponentially by the hour. Originally I thought they were crazy Rasberry ants, but they look more like these rover ants. We're calling our pest control company tomorrow morning. We'll recommend the INTICE THIQUID.

We talked to the pest control company and they do not treat ants in cars. However, their receptionist had the same problem with rover ants in her car. She put her car in the garage with the garge door closed then opened the doors of the car and set off a Raid bomb. Apparently that did the trick. Since we have an infant I felt like this wasn't the best option for us. Instead we put some Torro liquid ants baits in the car, put the car in the garage with the car doors closed, and set off a bomb. I have yet to see another ant, but we plan to leave the car in the garage with the baits in there for a few more days just to make sure. We'll probably set off another bomb in the garage in a day or two as well just to be sure they are all dead.

I had also talked with ABC and one recommendation, which may be helpful is they told me not to spray. They said that if they feel threatened that you could 'fracture' the colony and they'll split 1 colony into 3 and you'll expand your problem...maybe one of the pest control guys can confirm this for you...does anyone know if you can buy this Intice or does it require a license?

Ive had the most sucess baiting with terro liquid, i then follow the trails back to the nest or entry and treat with termidor or suspend

I live in Flower Mound, Texas and the rover ants came in the spring. They would show up on the kitchen counter, come thru the telephone jack, from under the molding. I would find the majority of them in the bathroom sinks. They were both upstairs and downstairs. I spent $150 with a pest control company who told me upon seeing the ant that they were very difficult to get rid of because it was hard to bait them. The article above gave me some insight on where to look for them outside my house under stone and along concrete.

Here is how I got rid of them.

To stop them immediately from entering the house, I used an insecticide we've used with great success in the horse barn. It's called Tempo. Tempo is animal safe and can be used where food is prepared. I mixed a gallon of the concentrate and saturated the exterior of my house along the concrete and stone where they might be living. I saw immediate results in that we had no more large invasions but there were still ants in the I knew some nests were inside the brick.

About a week after spraying and with a lot of patience, I watched and watched to see where they were leaving/entering the kitchen and bath. Once I found where, I went outside and watched and watch and then I saw 2 on the brick as they moved into the smallest hole in the mortar.

I used Thiquid InTice $15.50 and put a line of the bait on the concrete close to where they where entering the brick. I was amazed how fast the first ant took the bait. He ate and went into the hole and 10 ants came out, they eat went back and for hours the ants took the bait.

I laid down 4 areas around my house including the stone in my landscaping where there where many. I am ant free for now. I really hope this helps you. Remember, the trick is patience and observation just don't kill the scouts...follow them...bait them...kill them!

All the Best

I live in Hutto, TX and I have had ABC Pest Control come out to my house more times than I care to admit. When it comes to creepy crawly bugs, I go nuts. After spoting these rover ants in my house I have been itchy scratchy for months now and even a tiny speck of dirt makes my skin crawl because I worry it will be these ants.

I am finding them in all places in my home that are supposed to be clean - they love the inside of my dishwasher whether the dishes are clean or dirty (makes me sick to my stomach and I prewash every dish now before I use it), they are all over my shower walls, bathroom sink counters, and oddly enough my toilet paper roll hanging on the wall. I find them crawling along the top of my kitchen counter and in between the tiles of my backsplash.

ABC has placed baits in my home in the places I have found them in but like others have said - it works for a couple of days and then they come back in full force. In wild fits of anguish, I have found spraying them directly with Windex works well.

I'll have to pass along this information to ABC to see if they can try any of these recommendations. I'm at the point where the ants are winning and they can just have my house. I can't fight them anymore.

By Courtney E (not verified) on 15 Jun 2009 #permalink

Well, well, well. It seems that I now have a name to the nasty little pests in my pantry. Just what we need, a new bug in Houston. Terrific.

We've had quite a dry spell lately, along with high temps-- so perhaps they are looking for food/water.

They resemble little coffee ground specks...that is, until you see them moving. I didn't even know this was a true ant until I could get my macro working and saw it was a six-legged, segmented insect. The abdomen is really the give-away. It's so bulky compared to other ants.

These are pics of ours.

UPDATE to my previous post.

I am still ant free in my house. It's been about 3 weeks. I sealed the tiny holes in the mortar with that expanding foam you get at Home Depot once I saw no more activity. Next, I attacked the landscape stone that lines my flower beds. I should have taken a picture of the hundreds of ants that came to feed on the Thiquid Incite bait. Please try this stuff...I got my home back! Now I got problems with Geckos but my kids freak out less with them.

Best of Luck!!

Also a really good bait to use on these guys in Dupont Advion Ant Gel you will want to use this inside where you see they are trailing in from. Just put a lil dot in there path and they will all line up on it. On the outside go around the perimiter of your house with a granular insecticide. And finally use a dust insecticide in the weep holes on ur house or in the brick. This is how i use to treat for them when i was a pest control technician in Dallas,Tx. *This is my advice for you to tell your local pest control service*

I've had these ants in Kyle TX for 2 years now. Terminix couldn't even identify them, much less kill them, but ABC took care of it immediately with Intice Thiquid. They swarmed the bait and consumes it entirely within 45 minutes! Combat ant gel seems to work well as well. They are ALWAYS outside here, and so abundant I can't imagine killing all of them without causing a lot of collateral damage or poisoning the entire neighborhood. I heard some people keep them away from their houses by setting up self-watering globes away from the foundation. I will try this as well.

I am so glad I found out what these little buggers are...they are EVERYWHERE at my house in East Texas (Quitman) - inside and outside. We try not to use any chemicals on our property because we have numerous underground natural springs...I have tried DE, and corn meal and neither worked, it was like they found another way around the DE, since it kills pretty much on contact...but they do seem to love sugared water...they attack the hummingbird feeders within minutes of me hanging them. I guess I will have to try the gel traps and see what happens. If you have had sucess with non-chemical items, please post so I can try as well.

Lynn, I am not sure if was coincidence that they were gone or if it was the stuff I used, but I posted above about them being in a child's bedroom. I used this:, the active ingredient is mint oil. Very strong mint smell. I also used it in the kitchen. After using this, I haven't seen any for about a year now. *knocks on wood* :)

I don't know if you are looking for something for in your home, or outside. I wonder if mint plants would deter them outside?

I had such a battle with them I still am always keeping an eye out for them in the house. I still see them outside so I know they're out there and I worry they will come back inside some day. I would try the Safer Poison-Free again if they do.

Cari - did you find the Intice Thiquid locally or did you order it online?

I am also in North Texas (Irving/Coppell area), and these buggers have taken over my apartment. They pest control persons have been out 4 times, and the bait they use do not work. The ants may disappear for about a week, but then they reappear even more finding more cracks and crevices to come out of. SO annoying!

In Houston, TX, I work in the center of the second (top) floor of a large building, I have no exterior walls as my entire office block, of which I am the center, is completely surrounded by corridors, the same layout on both floors. I usually see no ants on my desk, as you'd expect, but if I set an open can of Dr. Pepper on my desk, within minutes there will be rover ants on it. Sometimes they'll wander by regardless, sometimes wandering on my arms. Facilities said they're sending someone out with gel baits.

One more note, at home I've noticed that when you use Amdro to kill a fire ant mound, rover ants move in the empty nest very quickly.

My exterminator just put the gel bait in my kitchen for the rover ants. Ewwww... I can't stand them!!! Although I don't know if they look like these pictures, they are so tiny. I'll have to try to catch a few of them and stick them under a microscope. He says they are very popular in this area (Houston) and come inside because they seek moisture.

Well, I'm sad to report the ants have returned. *sigh*

I live in Houston. Rover ants have been driving me nuts for about 4 months. After talking to a neighbor, he recomended Terro Ant Killer.

It's available everywhere and it's only $3.95.

I tried some he gave me, and it got rid of them in 2-3 days.

Simple to use, and inexpensive. It's a gel and you just put a drop or two right in their path. They love the stuff. Gangs of them will come pretty quick and take it back to the nest, and they all DIE! Haven't seen any more. It's only been a few days, but it's the first few days I haven't seen any in a long time.

Good luck!

Ahhh! I have these rover ants in my bathroom. They were treated once by ABC and resolved after two treatments (including gel, ?name?), but now they are back!! They seem to be coming out of the sink edge and from around the bathtub. I have an infant son and they were all over his changing pad (on the bathroom counter) - I was disgusted. I am going to have ABC come out again, but I am discouraged to read that they are so persistANT. GROSS!!!!!!! I feel like they are crawling on me! I try to resist killing them but every time I see them, I shoot them with a bleach solution. Makes me feel better to see them dead, but now I realize I may be doing more harm than good.

Oh, and we live in central Austin, FYI.

All the advice provided is much appreciated!

thanks for all this information. i just ordered INTICE THIQUID from for $15.50 and am hopeful that it will work!

Do you have a literature citation for statement that "Brachymyrmex patagonicus appears to be spreading in the southeast and has recently arrived in various western cities. I would not be surprised if it is already established in San Diego and Los Angeles"?

Am particularly interested in documenting spread of range in AZ (beyond Tucson) and spread into southern California.

By D A Reierson (not verified) on 04 Dec 2009 #permalink

My exterminator just told me the ants in our house are rover ants. He put down intice gel, hope it works. FYI, I live north of Houston on Lake Houston and have had the ant problem for about 2 - 3 months.

According to gardeners I've talked to, these ants emerged in huge numbers here in Tucson about 5 years ago. Given the interest in this species, I thought I'd post a summary of what we know of this emerging pest and how to reliably identify it.

Do you have a literature citation for statement that "Brachymyrmex patagonicus appears to be spreading in the southeast and has recently arrived in various western cities. I would not be surprised if it is already established in San Diego and Los Angeles"?

Am particularly interested in documenting spread of range in AZ (beyond Tucson) and spread into southern California.