Fire ants invade Europe?

Solenopsis invicta has officially arrived in Europe. This species, known as fire ants, which is among the most aggressive in the world, was discovered for the first time in the wild on European soil by a team of Spanish and Italian scientists, who reported it in an article published by the journal Current Biology Monday, September 11.

“We first received images from a resident of the Syracuse area in Sicily, who complained of being bitten by an ant, and the accompanying images looked like fire ants,” says Mattia Menchetti, a researcher at the Institute of Evolutionary Biology in Barcelona and lead author. From this article.

About 100,000 fire ants around Syracuse

Then he and his team went there, at the end of 2022, to determine whether it was indeed Solenopsis invicta, a reddish-brown ant up to 5 millimeters in size equipped with an arrow feared around the world.

There’s no doubt: In total, 88 fire ant nests were found. Knowing that a single nest can easily contain more than 1,000 ants, “we estimate that there were actually about 100,000 ants in an area of ​​4.7 hectares,” says Mattia Menchetti.

This first contact does not mean that the invasive species has just set foot on Italian soil. “Testimonies from local residents indicate a presence that may date back to 2019, which we have not been able to confirm,” explains this evolutionary biologist.

Olivier Plait, a specialist in invasive species at the University of Avignon, says this confirmation of the presence of fire ants in Europe “raises concern when we observe the very negative impact of this species elsewhere in the world.”

Native to South America, this tropical insect is classified as… Top 10 most harmful invasive species For humans, in the latest baseline report of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) published in early September 2023.

Before building its first nests in Europe, Solenopsis invicta was largely settled in North America, Asia, and Oceania for a century. Olivier Plait points out that its presence costs billions of euros every year, “either because of its direct impact on the economy or in the expenses of trying to eliminate it or control its spread.”

If in its native home in South America these little ants encounter other species that have learned to defend themselves against them, this is not the case at all in the new areas where they settle. Mattia Menchetti confirms that these organisms face little competition, and “harm local biodiversity by imposing themselves at the expense of other species.”

Strong poison

These losses to biodiversity result in significant economic costs, as shown OECD in 2019 report. But the fire ant “also has a significant health impact due to its sting, which contains a powerful venom,” emphasizes Gemma Trejos Peral, a specialist in biodiversity and ants at the Museum and Zoological Institute of the Academy of Sciences. .

“Not only is their sting extremely painful, but there are cases of anaphylactic shock every year. [réaction allergique brutale, NDLR]”, adds this expert.

Humans are not the only ones affected. “These ants are capable of causing serious injury or even killing small livestock,” notes Gemma Tregus Peral. For this reason, agriculture and livestock are often the main victims of its spread.

There are many reasons to try to get rid of these invasive little critters as quickly as possible. But success stories in this field are rare. United States and Australia spends hundreds of millions of euros Every year without being able to get rid of it. Only the New Zealanders were able to eliminate it, but “only because they did it at the right time,” Olivier Plait asserts.

In fact, this species can reproduce very quickly without quick action to get in its way. On the one hand, it is a type of ant “capable of forming supercolonies,” as Olivier Plait points out. In most non-invasive species, two neighboring nests compete until one conquers the other. This is not the case with fire ants. “The energy saved in this way can be used for reproduction,” sums up the specialist from the University of Avignon.

These super colonies can become very impressive. In the case of the Argentine ant, which is also found in Europe but is less destructive, There is one that spans more than 6 000 km.

On the other hand, Solenopsis invicta accepts several queens in one nest, which is far from the case in most ant species. Here again, this is a great population accelerator.

Finally, fire ants can also naturally spread over several kilometers. This means that they do not necessarily need to be transmitted by humans to ensure their spread. The error is that queens make nuptial flights, while in other species they mate in the nest. Thus, the “queens of fire” can lay their eggs kilometers away from their original den… and find a new nest there.

When this type is discovered, a race against time begins because it is “a classic case of a situation in which inaction costs more than action,” as Olivier Plait emphasizes.

In the city while waiting for global warming

Europe has long believed itself safe from the invasion of these tropical insects which, in order to survive, need a climate warmer and more humid than that which dominates much of the ancient continent. But due to global warming, there will now be 7% of European territory where a fire ant can feel comfortable, and almost 50% of urban areas, including cities such as Paris or London.

But the experts interviewed by FRANCE 24 stress that we should not blame everything on global warming. “Their arrival in Europe is primarily due to the globalization of trade – fire ants generally arrive via commercial ships – and global warming is only facilitating their spread,” explains Mattia Menchetti.

For his part, Olivier Plait specifies that cities represent “bridgeheads” for the spread in areas that are not yet climatically acceptable for these tropical insects. Indeed, urban centers form suitable “micro-climates” for these insects: when it is very cold in urban areas. In winter, they find refuge in buildings, and if the summer is too dry for their liking, they only need to find pockets of moisture. They just have to wait between two buildings until global warming turns all of Europe into a playground.

In this regard, it is perhaps “fortunate that the first nests were discovered on an island like Sicily,” believes Gemma Trejos Peral. There are fewer large urban centers and water can slow the natural spread. Olivier Plait believes that “if the presence in Europe is limited to this area, its eradication using insecticides is still quite possible.”

But still, the Syracuse suburbs marked the beginning of this invasive species’ European adventure. “Usually, when we start hearing about these ants’ stings, it’s because they’ve been there for some time,” says Gemma Trejos-Peral. Maybe they had time to expand their scope.

Above all, “this is not the first time we have seen fire ants in Europe,” emphasizes Olivier Plait. This has been seen in shipments of exotic plants arriving at ports, particularly in the Netherlands. And every time they were intercepted.

But some may have gone unnoticed. In this case, the discovery of Syracuse would serve as confirmation. However, it is urgent to know what to do: is there still time to eradicate the insect or should we above all try to control its spread? For this reason, it is necessary, according to Mattia Menchetti, to “appeal to the population” by asking them to report their stings and to send any photo of an ant that looks red or suspicious.