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.

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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.


sources:
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.