Solenopsis invicta swarm
Invasive species are organisms that don't naturally occur in a location and might or might not damage the local natural biome. Often these invasive species are introduced by human actions and happen to find perfect conditions (natural or due to climate changes) for developing to a point where they start to influence the environment by competing with local species, predating them, or even bringing new diseases.
This of course also applies to ants. Nowadays with the global logistics network it's impossible to keep every shipment free from unwanted visitors. But the irresponsible or illegal commerce of exotic species for the hobby can also increase these problems.
The biggest invasive ant species worldwide are: Anoplolepis gracilipes, Solenopsis invicta, Wasmannia auropunctata, Pheidole megacephala and Linepithema humile. All these are known invasive species in The Netherlands and the last two are even registered to have settled here, partially because these species are adapted to survive the colder weather even when nested outside.
Tapinoma nigerrimum worker
Lately though, the Tapinoma nigerrimum population is getting more and more media attention as a fast-spreading issue, especially in city environments where they can easily survive the winters (between walls and inside buildings).
It's unclear how this species got here but the registered Tapinoma nigerrimum nests in The Netherlands has tripled between 2019 and 2021.
Anoplolepis gracilipes carrying for aphids. Photo by ©Lynette
Invasive ants often abuse the mutualistic interactions with local species in a way that both species can thrive and grow, but that doesn't necessarily mean a good thing.
Think about crazy yellow ants (Anoplolepis gracilipes) that can take over a biome by partnering with the local aphid population, both these populations will profit from this relationship and thrive.
Eventually the ants will need more protein and can quickly decimate local animal populations (invertebrates and small reptiles). The local flora will also be negatively affected by the explosive growth of the aphid population.
These invasions can quickly change the environment in such a way that within a few generations the complete biome might be disrupted beyond repair.
Another notorious invasive species are the red imported fire ants (Solenopsis invicta), a South American species widespread over the world. These ants can develop massive colonies and are extremely aggressive against bigger animals, they clamp onto the victim with their jaws and can sting multiple times, injecting a painful venom which can be quite dangerous for young kids and people susceptible to allergies.
Solenopsis invicta also feeds on buds from crop plants like soy and corn, making them accountable for huge losses in the agricultural sector especially in North America and Australia.
Solenopsis invicta workers. Photo by ©Vitaly Charny
Invasive species like the Argentine ant (Linepithema humile) are famous for creating super colonies, due to the polygynous nature of these species, given the right conditions they will keep growing and spreading as long as there's space available.
Linepithema humile worker
Linepithema humile is native to the south of Brazil, bordering Argentina and Paraguay and has been spread worldwide by irresponsible commerce.
The largest recorded ant colony in the world is from this species, in 2002 it was registered to spread for more than 6.000 km in the Mediterranean region!
This super colony was then estimated to have millions of nests and billions of workers working single minded, as one.
New studies in 2009 demonstrated that this super colony surprisingly belongs to one single 'mega colony' spread over Japan, North America and Europe, all ants containing the exact same DNA traits. This makes Linepithema humile the most populous society on record, besides humans.
Some native species can also be misinterpreted for invasive due to their behavior in a city environment, correct identification is therefore important before any actions are taken, in general the common signs of invasive species (in city environment) are:
- year-round workers activity inside the house
- unusual large presence of workers on food sources
- no visible nest, workers seem to come from different places
- decaying of garden plants (due to increased aphid activity)
It's important that us, ant-enthusiasts, do our part by legally acquiring ants from legitimate sellers and taking full responsibility for the exotic species under our care: studying about them beforehand, using appropriate and enough anti escape methods and providing the best possible environment for them so they don't feel the need to look for better conditions.
We can also help by reporting when we spot and identify any invasive species during our ant hunts.
By suspicion of invasive ants' activity at home report to the local municipality and/or a plague control company.
Pheidole megacephala workers with major. Photo by © Alex Rebelo
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