Invasive red fire ants have made their way to Europe and are poised to takeover

A red fire ant species with a painful sting (Solenopsis invicta) is one of the most invasive species on Earth. Native to South America, these red fire ants have recently spread across the globe. 

Now, a team of scientists led by the Institute of Evolutionary Biology (IBE) in Spain has confirmed that this species has reached Sicily and could soon spread all over Europe, possibly causing major environmental, economic, and health problems in Italy and beyond.

Alarming spread of red fire ants

“S. invicta is one of the worst invasive species. It can spread alarmingly quickly,” explained lead author Mattia Menchetti, a PhD student at IBE. “Finding this species in Italy was a big surprise, but we knew this day would come.”

Previously known as “the imported red fire ant,” this species’ scientific name comes from its most infamous feature, its painful stings that can sometimes cause anaphylactic shock. 

How are they spreading?

Although it is native to South America, red fire ants have spread rapidly by flying into wind stream to travel farther on the local level. 

Humans have also played a major role in the insect’s global spread through the maritime trade industry and by shipping plant products, helping it establish throughout the United States, as well as in other regions, such as Australia, the Caribbeans, China, and Mexico. However, this is the first time that the ant has been spotted in Europe.

Alien ant species

“There are a vast number of alien ant species currently establishing in Europe, and the absence of this species was kind of a relief,” Menchetti said. “For decades, scientists have feared that it would arrive. We could not believe our eyes when we saw it.”

After seeing several photographs taken in Sicily of what looked strikingly similar to S. invicta, the experts travelled to the region to confirm the ants’ identity. 

Red fire ants have painful stings

They discovered 88 nests in a 4.7-hectare area close to a river, some of which contained several thousands of working ants. Sicilian residents told them that they had been getting stung frequently by such ants 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,” said Menchetti. “And the real extension of the invaded area is probably larger.”

First entry point in Europe

Although scientists discovered the ant in Europe for the first time, they suspect that Sicily wasn’t the insect’s first point of entry on the continent.

While they could not yet determine how it reached Europe, an analysis of the Sicilian ants’ DNA revealed similarities to red ant populations in the US and China.

Predicting the future spread of red fire ants

To better understand how the ants might spread around Europe, the researchers analyzed the local wind patterns in Sicily and designed a comprehensive model to determine how suitable the rest of Europe and the Mediterranean region will be for this species and what role might climate change play in the ants’ further spread.

What the researchers learned 

The analysis revealed that, although only seven percent of the European continent is suitable for S. invicta given current environmental conditions, climate change will likely expedite their spread and population growth in other areas too. 

Moreover, researchers found that urban regions, particularly in Europe, were especially at risk, with 50 percent of Europe’s cities 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 senior author Roger Vila, an evolutionary biologist at IBE.

Eradication plans

Since the only place where the red fire ants were successfully eradicated is New Zealand, the experts plan to base their interventions on methods that worked there, as well as on efforts underway in China. 

First, they will systematically inspect local areas to assess whether the ants have already reached them. Next, the plan is to initiate a multi-year treatment to eradicate the red fire ant nests. Finally, they will monitor the invaded sites to ensure that there are no resurgences. 

In these efforts, the public should play a critical role in helping monitor the insect’s spread. “Citizens can play a very important role in this,” Menchetti explained. “We hope that, with their help, we will be able to cover a wider area. This will help us track and spot all the possible areas invaded in the region.”

Citizen science programs 

Thus, the researchers plan to organize citizen science programs in which people would take photos of the ants. However, since many European ants build similar-looking nests, the experts will double-check the citizens’ findings. They need to make sure that they discovered the right ant species and are actually reporting red fire ant sightings.

“There needs to be more awareness about this problem because the problem is already in Europe. We need coordinated action, and we need it now,” Menchetti concluded.

The study is published in the journal Current Biology.

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