Fire ants launched their global invasion through the United States

Solenopsis invicta

The famously pesty South American fire ant (Solenopsis invicta) has plagued the southern regions of the United States since the 1940s. Although they achieved legendary status as one of the most damaging insects in the United States, for half a century they never moved beyond the North and South American ranges.

About 10 years ago, though, all that changed.  Solenopsis invicta suddenly started appearing elsewhere: Taiwan, China, Australia. Did these arrivals mark a new wave of invasion from South America, perhaps hitchhiking on the global soy trade?

Genetic data reveal the global spread of fire ants from the southern U.S. (Figure from Ascunce et al 2011)

A new study by Ascunce et al in this week’s Science answers that question with a resounding No. It turns out the Asian invasions are our fault. The dense fire ant populations in the United States served as a launch pad for all three Australasian incursions.

source: Ascunce, M.S. et al 2011. Global Invasion History of the Fire Ant Solenopsis invicta. Science 331: 1066-1068 DOI: 10.1126/science.1198734

14 thoughts on “Fire ants launched their global invasion through the United States”

  1. Weird, I thought this was already known. Cool to see my good buddies (the fire ants) back in the pages of Science, though.

    1. US Exports $1.280 trillion f.o.b (2010)

      US Export goods agricultural products (soybeans, fruit, corn) 9.2%, industrial supplies (organic chemicals) 26.8%, capital goods (transistors, aircraft, motor vehicle parts, computers, telecommunications equipment) 49.0%, consumer goods (automobiles, medicines) 15.0% (2009)

      Total GDP $14.660 trillion

      Total US debt held by China about $ 950 billion = 6% of annual GDP

  2. It does seems quite likely that the US populations of Solenopsis invicta were the source of the Asian infestations. After all, that’s where all the trade volume is and increased frequency equals increase probability.

    However, I would suspect that it’s much more likely that those Asian countries themselves were “at fault”, since the US has minimal merchant capacity to that part of the world. How a foreign merchant carrier or a foreign port deals with quarantine issues is hardly a US responsibility.

    Therefore I would disagree that “It turns out the Asian invasions are our fault”, unless you are referring to humans in general. For that matter, we humans suck in general in preventing inadvertent hitchhikers simply because of ignorance, laziness and parsimony.

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  4. Hi,

    I wonder why they haven’t come to Europe yet? At least in southern European countries the average temperature should be high enough.

    The US also exports a lot to Europe, so why haven’t they invaded yet?.

    1. It’s not all about temperature. These ants like it hot and humid. In the US, they are much less prevalent, indeed absent, from the greater part of the more arid warm regions. Mediterranean Europe is also relatively arid.

      1. Thank you for your reply. I asked since we had a discussion about this topic a few month ago in an ant forum. Nobody knew the answer.

        Some people there even think they could establish in Central Europe.

    2. Marc "Teleutotje" Van der Stappen

      They entered Europe already a few times but or they were intercepted in carantine or they couldn’t survive outdoors. Not much is published about their situation in Europe. The only thing I know of is about the Exotic ants in The Netherlands ( , see table 2) with 2-5 temporary settelments since 1957.

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