Entomologists Find Population of Invasive Red Fire Ants in Italy

Entomologists Find Population of Invasive Red Fire Ants in Italy

The red imported fire ant (Solenopsis invicta) is one of the worst invasive alien species and the fifth costliest worldwide, impacting ecosystems, agriculture and human health.

Researchers from the Institute of Evolutionary Biology at the CSIC-Pompeu Fabra University have now documented 88 nests of red imported fire ants — for the first time in Europe — near the city of Syracuse in Sicily, Italy.

The ants could soon spread all over the continent, the researchers warn, which could cause major environmental, health, and economic problems in Italy and beyond.

“Solenopsis invicta is one of the worst invasive species. It can spread alarmingly quickly,” said Dr. Mattia Menchetti, lead author of the study.

“Finding this species in Italy was a big surprise, but we knew this day would come.”

Solenopsis invicta’s common name comes from its most infamous characteristic — its stings — which are painful and, occasionally, may cause anaphylactic shock.

Although it originated in South America, Solenopsis invicta has spread quickly, flying into wind streams to travel farther on the local level.

But humans have also helped it spread both through the maritime trade industry and by shipping plant products, enabling it to establish in Australia, China, the Caribbean, Mexico, and throughout the United States in less than a century. Europe has evaded them for longer than expected.

“There are a vast number of alien ant species currently establishing in Europe, and the absence of this species was kind of a relief,” Dr. Menchetti said.

“For decades, scientists have feared that it would arrive. We could not believe our eyes when we saw it.”

After seeing photos taken in Sicily of what looked like Solenopsis invicta, Dr. Menchetti and colleagues took a trip to the region to confirm the ants’ identity and collect samples.

They found a total of 88 nests in a 4.7-hectare area next to a river, some of which housed many thousands of worker ants, near the city of Syracuse in Sicily.

After speaking with locals, the researchers learned that people in the Sicilian region had been getting stung — and frequently — for several years.

“The locals have been experiencing these painful things since at least 2019, so the ants have probably been there for a while. And the real extension of the invaded area is probably larger,” Dr. Menchetti said.

Analyzing the DNA of the Sicilian queen ants and comparing it with the genomes of ants from all over the world, the researchers concluded that this particular population likely came from either the United States or China.

Next, they analyzed the local wind patterns in Sicily to see how the ants might spread now that they’re in Europe.

They also put together a comprehensive model to determine how suitable the rest of Europe and the Mediterranean area will be for the species — and whether climate change will be a factor.

According to the model, 7% of the European continent is suitable for Solenopsis invicta given current environmental conditions, and climate change will likely expedite their spread and population growth even further.

They also found that urban areas are particularly at risk. In fact, 50% of Europe’s cities are vulnerable to invasion.

“This is especially concerning because many of the cities, including London, Amsterdam, and Rome, have large seaports, which could allow the ants to spread rapidly to more countries and continents,” said Dr. Roger Vila, senior author of the study.

The team’s work was published in the journal Current Biology.


Mattia Menchetti et al. 2023. The invasive ant Solenopsis invicta is established in Europe. Current Biology 33 (17): 896-897; doi: 10.1016/j.cub.2023.07.036

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This article was first published by Sci-News on 12 September 2023. Lead Image: The red imported fire ant (Solenopsis invicta). Image credit: Alex Wild / University of Texas Insects Unlocked program.


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