What we know about “Tapinoma magnum,” the shiny black ant invading Europe
Numerous invasive infestations of the black ant *Tapinoma magnum* have been detected in Europe. While they do not pose an immediate health risk, the massive populations within each colony can cause considerable damage in urban, agricultural, and even natural environments. In hopes of stemming this invasion, researchers are now working to better characterize it, assess its impacts, and explore ways to limit the damage.
Bernard Kaufmann, Claude Bernard University of Lyon 1; Alan Vergnes, University of Montpellier; Giovanny Destour, University of Montpellier and Marion Javal, French National Research Institute for Sustainable Development (IRD)
The term "biological invasion" refers to the introduction and proliferation of animal, plant, or microbial species outside their native range. Most invasive species disrupt ecosystems by competing with native species and subsequently altering habitats. They represent a growing economic burden for human societies and a threat to biodiversity.
Among these species, ants play a prominent role. Until now, Europe and France had been relatively spared, despite the presence of the Argentine ant ( Linepithema humile ) along the Mediterranean coast and Lasius neglectus throughout the continent. Recent alerts raise concerns about the establishment of the red fire ant (Solenopsis invicta), detected in Sicily, and the electric ant (Wasmannia auropunctata), detected twice in the Var region—two species that have caused major damage to agriculture, people, and biodiversity wherever they have been introduced.
But it is another species that is currently attracting attention in Western Europe: Tapinoma magnum. Numerous invasive outbreaks have been detected, with massive populations causing considerable damage. It is now urgent to understand its characteristics, its impacts, and the state of research in France, and to explore ways to limit the damage it causes.
The discovery of supercolonies
In 2011, researchers and naturalists in France, Germany, and Italy discovered ants of the genus Tapinoma (abbreviated as T.) that turned out to be highly invasive. A European working group was quickly formed, with teams in Görlitz (Germany, B. Seifert), Rome (Italy, D. d’Eustacchio), Jaén (Spain, P. Lorite), and Lyon (France, B. Kaufmann).
To date, only one species of the genus, T. nigerrimum—which is relatively large compared to other species in the genus (2–5 millimeters)—is known in Mediterranean Europe and northwestern Africa, but the scientific literature does not describe it as invasive. However, in the field, the observed colonies consist of numerous nests interconnected by trails constantly traversed by workers, forming a dense network that can cover several hectares, constituting what are known as supercolonies, which are highly invasive.
In 2017, an analysis combining detailed morphological and genetic data revealed that T. nigerrimum actually comprises at least four distinct species: T. nigerrimum, T. darioi, T. ibericum, and T. magnum.
These last three are supercolonial and invasive species in Europe, with T. magnum being by far the most common. In 2024, a fifth species, T. hispanicum, was added, encompassing Spanish populations of T. nigerrimum (non-invasive).
From diverse backgrounds
Based on what is known about these invasive ants, T. darioi is native to Catalonia and likely to the Languedoc region, while T. ibericum is likely native to the rest of Spain.
For T. magnum, the situation is more complicated, as its possible areas of origin span the Maghreb countries (Morocco, Algeria, and Tunisia) and the entire Italian peninsula, possibly extending as far as the French Riviera.
Genetic analyses show, however, that the vast majority of populations that migrated to non-Mediterranean regions of Europe originated in southern Italy, particularly Sicily, Calabria, and Apulia. Only very few populations have been linked to the Maghreb. As for Corsica, the populations appear to have originated in southern Italy, with perhaps some minor Algerian influence.
Colonies covering up to 20 hectares
T. magnum and its invasive sister species are supercolonial: their numerous nests, connected by active tunnels, can house many queens. Built by piling up soil to create “solariums” exposed to heat, or located in warm cavities, these nests optimize larval growth. Males and future queens are produced in the spring (between March and May), while workers are produced later in the spring and in the fall.
The supercolony is a fluid entity whose boundaries expand or contract depending on temperature, humidity, and available resources, sometimes covering more than 20 hectares, unless the landscape (roads, waterways, forests) limits its expansion. The diet of invasive Tapinoma ants is omnivorous, but relies heavily on the consumption of aphid honeydew, particularly from roots.
When the first reports emerged outside the Mediterranean region, the trade in century-old olive trees from Italy and Spain was quickly suspected of being the primary source of the invasive populations. This hypothesis was confirmed by a study conducted with plant sellers in Montpellier and Lyon, which showed that a significant number of them harbored one or more invasive Tapinoma species, often fromdifferent geographic origins.
However, recent observations point to other potential modes of transport: cars that ants may climb into during the day to find warmer temperatures, the transport of green waste, the movement of ornamental plants for events, and the transport of prefabricated structures.
Black, shiny, and very fast
Invasive Tapinoma ants are easy to identify in the field: they are shiny black, extremely fast ants, whose workers within the same colony range in size from 2 mm to 5 mm.
When crushed, they have a distinctive odor, described by ancient authors as reminiscent of rancid butter. This characteristic alone is not sufficient for identification. T. nigerrimum, which is native and harmless, shares these characteristics, and other smaller species (T. erraticum, T. subboreale, T. madeirense) have the same odor.
To be sure you’re dealing with an invasive Tapinoma colony, you need to see several nests connected by ant trails.
Distinguishing between the three invasive species requires our laboratories to employ additional genetic, chemical, and imaging methods.
Damage to urban and agricultural areas
First and foremost: while Tapinoma ants may be annoying, they do not pose a proven health risk, except for very young children who come into direct contact with large nests.
However, invasive Tapinoma species cause damage in natural habitats as well as in urban and agricultural areas, with direct and indirect negative effects on biodiversity that have not yet been quantified but are likely significant.
In commercial vegetable farming and in home gardens, ants turn over large amounts of soil, exposing roots or burying stems. They cut leaves and stems, breed aphids in large numbers, and attack certain vegetables. Operational losses can be significant, especially in greenhouses: in the Drôme region, for example, an organic vegetable farmer saw his revenue drop by two-thirds.
For businesses, the widespread presence of ants in manufactured and exported goods can lead to their rejection or return; in the restaurant industry, ants can contaminate kitchens or drive customers away from outdoor seating areas. Parks and recreation departments have observed an impact on visitor numbers in the most heavily infested areas of parks, on the use of community gardens in Lyon, and on production greenhouses in Grenoble.
We expect these species to spread rapidly throughout the country and for their impacts to increase. Unlike other invasive species such as the Argentine ant and Lasius neglectus—particularly because Tapinoma species have been imported from multiple regions on numerous occasions and thus exhibit high genetic diversity—they possess significant adaptive potential. Their ability to establish themselves throughout the country is greatly enhanced by climate change.
Several research groups, including our own, are currently working to better understand these species and develop control strategies, collaborating with local stakeholders, organizations, and local governments. In our laboratories in Lyon (B. Kaufmann), Avignon (IMBE), Montpellier (CEFE, CBGP), and Tours (IRBI), we are studying their dispersal and proliferation mechanisms, their genetics, and their ecology, and we are developing control methods. Our research is expected to lead to the development of a control strategy and tools within the next two years.
What should you do if you suspect an infestation in your home?
For individuals who suspect they may have Tapinoma, here are a few tips:
- First, you must confirm that it is indeed an invasive Tapinoma species and have the species identified by a specialist by contacting the FIVALO project for the Centre region or Bernard Kaufmann for the rest of the country. This step is vital to avoid harming local ant species, which serve as the first line of defense against the invasion. This is particularly true in the southern half of France, where the local species T. nigerrimum is present.
- Next, contact your neighbors to find out if they’ve been affected as well so you can take action together afterward,
- then to their municipality or regional authority via a letter signed by all the residents concerned.
So, start taking action. There’s no need to call pest control, unless the infestation is limited to just one or two houses or gardens—just follow these three simple steps.
- First, look for nests (in the spring and fall) either in the ground or in garden items (dry compost, flower pots, planters, under roof tiles, pavers, rocks, metal, or garden tarps) or around the house (stairs, boiler room or laundry room, attic).
- Second, destroy them if possible by submerging them in hot water (60 °C) or large amounts of irrigation water (in which case, change the water frequently); if this is not possible, physically dislodge them with a spade and remove the favorable growing sites.
- Third, lure ants into makeshift "trap" nests: any of the garden items mentioned can serve as a trap. In the spring, ants raise their future queens, who need warmth and therefore sunlight. This is the time to eliminate them, in order to limit the number of reproductive ants in the following season.
For businesses, professionals, and local governments: the procedures described above require too much manpower to be sustainable, so there is no ready-made solution at this time. That is why it is important to focus on prevention, particularly for departments responsible for green spaces and for landscape architects.
Key precautions include checking for the presence of ants in green spaces, buildings, or waste disposal sites within the local area or on company premises; inspecting plants selected for landscaping or interior design; monitoring the transport of green waste or compost; and limiting the presence of ants in parking lots where they could climb into vehicles. Do not hesitate to contact laboratories for advice.
Bernard Kaufmann, Associate Professor of Ecology, Claude Bernard University of Lyon 1; Alan Vergnes, Researcher, University of Montpellier; Giovanny Destour, Researcher, University of Montpellier and Marion Javal, Researcher, French National Research Institute for Sustainable Development (IRD)
This article is republished from The Conversation under a Creative Commons license. Readthe original article.