What we know about Tapinoma magnum, the shiny black ant invading Europe
Numerous invasive colonies of the black ant Tapinoma magnum have been detected in Europe. They do not pose an immediate health risk, but the colossal populations of each colony can cause considerable damage in urban, agricultural, and even natural environments. In the hope of stemming this invasion, research is now underway to better characterize it, assess its impacts, and explore ways to limit the damage.
Bernard Kaufmann, Claude Bernard University Lyon 1; Alan Vergnes, University of Montpellier; Giovanny Destour, University of Montpellier and Marion Javal, Research Institute for 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 local species and then altering habitats. They represent a growing economic burden for human societies and a threat to biodiversity.
Among these species, ants occupy a prominent place. 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 fears of the arrival of the red imported fire ant (Solenopsis invicta), detected in Sicily, and the electric ant (Wasmannia auropunctata), detected twice in the Var region. Both species have caused major damage to agriculture, people, and biodiversity wherever they have been imported.
But it is another species that is currently attracting attention in Western Europe: Tapinoma magnum. Numerous invasive outbreaks have been detected, with huge populations causing considerable damage. There is now an urgent need to understand its characteristics, its impacts, the state of research in France, and to explore ways of limiting the damage it causes.
The discovery of supercolonies
In 2011, researchers and naturalists discovered ants of the genus Tapinoma (abbreviated to T.) in France, Germany, and Italy, which proved to be highly invasive. A European working group was quickly formed, with teams in Görlitz (Germany, B. Seifert), Rome (Italy, D. d'Eustacchio), Jaen (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 of the genus (2-5 millimeters), is known in Mediterranean Europe and North-West Africa, but scientific literature does not consider it to be invasive. However, in the field, the colonies observed consist of numerous nests interconnected by trails constantly frequented 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 morphology and genetics revealed that T. nigerrimum actually comprises at least four different species: T. nigerrimum, T. darioi, T. ibericum, and T. magnum.
The latter three are supercolonial and invasive species in Europe, the most common by far being T. magnum. In 2024, a fifth species, T. hispanicum, was added, grouping together Spanish populations of T. nigerrimum (non-invasive).
Diverse origins
From what we know about these invasive ants, T. darioi is native to Catalonia and probably to Languedoc, while T. ibericum is probably native to the rest of Spain.
For T. magnum, the situation is more complicated, as its possible areas of origin cover the Maghreb states (Morocco, Algeria, and Tunisia) and the entire Italian peninsula, possibly extending as far as the French Riviera.
However, genetic analyses show that the vast majority of populations imported into non-Mediterranean regions of Europe originate from southern Italy, particularly Sicily, Calabria, and Apulia. Only very few populations have been linked to the Maghreb. In Corsica, populations appear to originate from southern Italy, with perhaps a small contribution from Algeria.
Colonies covering up to 20 hectares
T. magnum and its invasive sister species are supercolonial: their nests, which are numerous and connected by active trails, can house many queens. Built by accumulating soil to create "solariums" exposed to heat, or installed in warm cavities, these nests optimize larval growth. Males and future queens are produced in the spring (between March and May), workers later in the spring and in the fall.
The supercolony is a fluid entity whose boundaries expand or contract depending on temperature, humidity, and resources, sometimes covering more than 20 hectares, unless the landscape (roads, waterways, forests) limits its expansion. The diet of invasive Tapinoma is generalist, but relies heavily on the exploitation of aphid honeydew, particularly on roots.
When the first reports came in from outside the Mediterranean region, the trade in century-old Italian and Spanish olive trees was quickly suspected of being the main source of the invasive populations. This hypothesis was confirmed by work with plant sellers in Montpellier and Lyon, which showed that a large proportion of them were hosting one or more invasive Tapinoma species, often fromdifferent geographical origins.
However, recent observations indicate other potential transport vectors: cars, which ants climb into during the day to find higher temperatures; green waste transport; the movement of ornamental plants for events; and the transport of prefabricated buildings.
Black, shiny, and very fast
Invasive Tapinoma ants are easy to recognize in the field: they are black, shiny, extremely fast ants, whose workers vary in size from 2 mm to 5 mm within the same colony.
When crushed, they have a characteristic odor, described by ancient authors as reminiscent of rancid butter. This diagnosis is not sufficient. T. nigerrimum, which is native and harmless, has the same characteristics, and other smaller species (T. erraticum, T. subboreale, T. madeirense) have the same odor.
To be certain that you are dealing with an invasive Tapinoma, you need to be able to observe several nests connected by ant trails.
Distinguishing between the three invasive species requires more genetic, chemical, or imaging resources to be deployed by our laboratories.
Urban and agricultural damage
First thing to remember: Tapinoma are annoying, but they do not pose a proven health risk, except for very young children in direct contact with large nests.
However, invasive Tapinoma species cause damage in natural environments as well as in urban and agricultural areas, with direct or indirect negative effects on biodiversity that have not yet been quantified but are likely to be significant.
In market gardening and private vegetable gardens, ants destroy large amounts of soil, exposing roots or burying stems. They cut leaves and stems, breed aphids en masse, and attack certain vegetables. Operating losses can be significant, especially in greenhouses: in the Drôme region, for example, an organic market gardener saw two-thirds of his turnover wiped out.
For businesses, the widespread presence of ants found in manufactured and exported goods can lead to their rejection or return, and in restaurants, they can contaminate kitchens or scare away customers from outdoor seating areas. Parks and recreation departments have noticed an impact on visitor numbers in the most infested areas of parks, on the use of shared gardens in Lyon, and on production greenhouses in Grenoble.
We expect these species to spread rapidly throughout the country and their impacts to multiply. Unlike other invasive species such as the Argentine ant and Lasius neglectus, Tapinoma ants have been imported from several regions on multiple occasions and therefore exhibit high genetic diversity, giving them significant potential for adaptation. Their ability to establish themselves throughout the country is greatly enhanced by climate change.
Several research groups, including ours, are currently working to better understand these species and propose control strategies, working in partnership with field workers, associations, and local authorities. In our laboratories in Lyon (B. Kaufmann), Avignon (IMBE), Montpellier (CEFE, CBGP), and Tours (IRBI), we are studying their mechanisms of dispersal and proliferation, their genetics, and their ecology, and are working on control methods. Our research should 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 several tips:
- First, you must ensure that it is indeed an invasive Tapinoma and have the species identified by a specialist by contacting the FIVALO project for the Central region or Bernard Kaufmann for the rest of the country. This is vital in order to avoid harming local ant species, which are the first line of defense against invasion. This is particularly the case in the southern half of France, where the local species T. nigerrimum is present.
- Then, contact your neighbors to find out if they are also affected so that you can take action together afterwards.
- then its municipality or intermunicipal authority by means of a letter signed by all the residents concerned.
So start fighting back. There's no need to call in pest control, unless the infestation is limited to one or two houses or gardens, but follow three simple principles.
- The first is to search for nests (in spring and fall) either in the ground or in garden objects (dry compost, flower pots, planters, under tiles, slabs, stones, metal, gardening tarpaulins) or along the house (stairs, boiler room or laundry room, attic).
- Second, destroy them if possible by drowning them in hot water (140°F) or large amounts of water (in this case, repeat frequently); if this is not possible, physically disturb them with a spade and remove favorable sites.
- The third method involves attracting ants to improvised "trap" nests: any of the garden items mentioned above can be used as a trap. In spring, ants raise their future queens, which need warmth and therefore sunlight. This is the time to eliminate them in order to limit the number of reproducers in the following season.
For businesses, professionals, and local authorities: the procedures explained above require too much manpower to be sustainable, so there is no ready-made solution at present. That is why it is important to focus on prevention, particularly for services responsible for green spaces and landscapers.
Essential precautions include checking for ants in green spaces, buildings, or waste disposal areas on the premises or within the company; inspecting plants chosen for green spaces 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, Senior Lecturer in Ecology, Claude Bernard University Lyon 1; Alan Vergnes, Researcher, University of Montpellier; Giovanny Destour, Researcher, University of Montpellier and Marion Javal, Researcher, Research Institute for Development (IRD)
This article is republished from The Conversation under a Creative Commons license. Readthe original article.