What’s the deal with Hairy Crazy Ants?

Nylanderia sp. "hairy crazy ants" (Buenos Aires, Argentina)

Several people have asked about recent news stories covering the “Hairy Crazy Ant” sweeping across the U.S. south. What’s the deal?

(AP)  NEW ORLEANS – It sounds like a horror movie: Biting ants invade by the millions. A camper’s metal walls bulge from the pressure of ants nesting behind them. A circle of poison stops them for only a day, and then a fresh horde shows up, bringing babies. Stand in the yard, and in seconds ants cover your shoes.


The AP is trying to be cute, but I think of this invasion in movie terms myself. It’s a sequel. And not even a good one. It’s one of those endless franchises that never dies, like Friday the 13th, and now we’ve moved on to Argentina Ant Horrors V: Hairier and Crazier.

The original movie- an 1890 classic- was Argentine Ants. Over a century ago, Louisiana was hit by a wave of pugnacious Linepithema humile, accidentally imported from Rosario, Argentina. The ants quickly spread across the warmer parts of the continent.

Argentine Ants was followed in 1940 by Argentina Ant Horrors II: Trial by Fire. The plot was the same: Formosa, Argentina sent us a six-legged plague, the infamous fire ants Solenopsis invicta. The invader spread coast-to-coast, everyone got stung, it was awful, blah blah blah.

The fire ant sequel was followed, predictably, by a pair of mediocrities copying the same tired script. Brachymyrmex patagonicus rover ants and Pheidole obscurithorax big-headed ants are both widespread in the southern U.S., and both are from- as best as we can tell- Argentina.

You’d think we’d be done by now. Sadly, no. Nylanderia pubens is the latest installment. An Argentine origin hasn’t been firmly demonstrated, yet, but I’d be surprised if they came from elsewhere. Species in the Nylanderia fulva/pubens complex are extremely common in subtropical South America. My little yard in Paraguay, back when I lived there, was full of them. And rover ants. And fire ants. And Pheidole obscurithorax, now that I think of it. It sounds so…familiar.

The gulf coast of the United States has a similar subtropical climate to northern Argentina. Ants from there do well here. What’s happening is nothing short of this: We are witnessing a great re-enactment of the northern Argentinian ant community along our own shores.

Here’s the problem for us, though. Argentina is home to a plethora of highly competitive ant species. They’ve got enough to send along another 5-10 sequels. Which invasion comes next?

My hunch is Crematogaster quadriformis, or Camponotus mus.

Coming soon? Camponotus mus, from Argentina.

Caldera, E.J., DeHeer C.J., Ross, K.G., Shoemaker, D.D. 2008. Putative native source of the invasive fire ant Solenopsis invicta in the U.S.A. Biological Invasions, 10: 1457-1479.

MacGown, J.A., Layton, B.  2010. The invasive Rasberry crazy ant, Nylanderia sp. near pubens (Hymenoptera:  Formicidae), reported from Mississippi (available online at:http://midsouthentomologist.org.msstate.edu/Volume3/Vol3_1_html_files/vol3_1_008.htm).  Midsouth Entomologist Vol 3: 1:  441-47.

Tsutsui, N.D., Suarez, A.V, Holway, D.A., Case, T.J. 2001. Relationships among native and introduced populations of the Argentine ant, Linepithema humile and the source of introduced populations. Molecular Ecology 10:2151-2161.

Wild, A. L. and A. V. Suarez. 2009. Mitochondrial DNA implicates the Paraná “invasion cradle” in another ant introduction-the South American big-headed ant, Pheidole obscurithorax. Oral Presentation, Entomological Society of America Annual Meeting, Indianapolis, IN, USA.

18 thoughts on “What’s the deal with Hairy Crazy Ants?”

    1. They seem to be a major problem for beekeepers; otherwise I’d call them more a nuisance. As to their effects on the native fauna, that’s a great question and not really known. After the fire ant & Argentine ant invasions it seems unlikely, in my opinion, they’d cause problems significantly beyond those stemming from the previous invaders. All the same, I’d feel better if someone was out there monitoring the effects.

      1. If they segment the trophic environment in Argentina/etc such that they co-exist on the same landscape then is is probable any additional species introduction will displace/impact additional native NA species in our environment.

        But eventually all new things become old, LOL.

        Good luck with that monitoring effort. Hard enough to do with plentiful money.

      2. It would be hard to do more ecological damage than the fire ants have already done. Fire ants almost wiped out the reptiles and amphibians in parts of the arid Southeast US, and ground-nesting birds also took a major hit. Endangered cave invertebrates in central Texas are threatened by them as well. The fire ants in Texas formed giant super-colonies with multiple queens and reduced territoriality, and achieved unbelievable densities and very fast recruitment against enemies or food. I pity any food item (especially something slowly emerging from a nice wet egg) withing biting range of these colonies (and EVERYTHING in southeast Texas is within biting range of these colonies).

        I watched (and fought) the invasion of Texas in the 80’s and 90’s. Perhaps things have stabilized now, or even recovered. Any Texan biologists out there have any good news about these damn things?

  1. I remember that well, Josh, as Buren and I had some interesting conversations about it. I think he might have published that tongue in cheek, to razz the USDA guys, of whom he did not have the highest opinion.

    And I know I shoudn’t say so, Alex, but Camponotus mus could be a pretty cool addition to our SE US fauna.

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    1. We have not, but we did send the mainland temperate species Tapinoma sessile (odorous house ant) to the uplands of Hawaii where (in the lowlands), many of these Argentinian species are also established.

      1. Thanks James.

        I wonder if this is interesting or if it just reflects a strong net balance of trade with products from Argentina coming into the US and not much visa versa?

        1. I think it’s interesting.

          I think South American ants are simply more competitive. And, I think that is because North American ants have evolved to deal primarily with abiotic stresses from a highly variable (=glacial) environment, while South American ants have had more stable environments over longer periods of time.

          Just my opinion, of course. These sorts of speculations are tremendously difficult to test in practice.

        2. Alex, I think there is something to the glacial component of your comment.

          But the contiguous subtropical AND tropical communities acting as a species source and refugia for southern hemisphere vs none on North America simply because of the shapes of the landforms likely also had a significant input. Less than 8 – 12 k yr is not a especially long time for community diversity development.

          More species to compete, more genetic source material available for ants in the tropics.

          It works in an opposite manner when you examine groups with Boreal distributions, Boreal maximal species diversity and abundance like Plecoptera.

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