Ants are among the most successful and diverse groups of insects on Earth, with more than 12,000 species described and many more undiscovered.
They are also highly social and cooperative, forming complex colonies that can range from a few individuals to millions of workers.
Ants play important roles in many ecosystems, as predators, scavengers, seed dispersers, soil engineers, and mutualists with other organisms.
However, not all ants are welcome in every habitat. Some ants have been introduced by humans to new regions, either intentionally or accidentally, and have become invasive pests that threaten native biodiversity, agriculture, and human health.
Invasive ants can outcompete, displace, or even kill native ants and other animals, as well as damage crops and infrastructure.
They can also alter the structure and functioning of ecosystems, reducing their resilience and stability.
Examples of invasive ants and their impacts
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Fire Ants
One of the most notorious invasive ants is the red imported fire ant (Solenopsis invicta), native to South America but introduced to North America, Australia, Asia, and other regions.
Fire ants are aggressive and have a painful sting that can cause allergic reactions in some people and animals.
They also form large colonies that can dominate the landscape, displacing native ants and other species.
Fire ants can damage crops, such as sugarcane and citrus, by feeding on plant tissues or protecting sap-sucking insects that they farm for honeydew.
Fire ants can also cause electrical failures by nesting in wires and equipment.
Argentine Ant
Another example of an invasive ant is the Argentine ant (Linepithema humile), native to South America but spread to Europe, North America, Africa, Asia, Australia, and many islands.
Argentine ants are highly adaptable and can thrive in a wide range of habitats. They form supercolonies that can span hundreds of kilometers, with millions of workers that cooperate and do not fight with each other.
Argentine ants can outcompete native ants for food and space, reducing their diversity and abundance.
They can also affect the populations of other insects, such as butterflies, bees, and aphids, by preying on them or interfering with their mutualisms with native plants.
These ants can also invade homes and buildings, where they can contaminate food and transmit pathogens
Yellow Crazy Ant
A third example of an invasive ant is the yellow crazy ant (Anoplolepis gracilipes), native to Africa but introduced to Southeast Asia, Australia, Pacific islands, and other regions.
Yellow crazy ants are named for their erratic movements and yellowish color. They have a powerful spray of formic acid that they use to subdue prey or deter enemies.
They can form supercolonies that can cover large areas and have high densities of workers.
Yellow crazy ants can have devastating impacts on native ecosystems, especially on islands where they have no natural predators or competitors.
They can kill or displace native ants and other arthropods, as well as vertebrates such as lizards, birds, and mammals.
They can also disrupt nutrient cycles and plant growth by altering soil chemistry and vegetation structure.
Yellow crazy ants have caused the decline or extinction of several endemic species, such as the red land crab on Christmas Island and the Seychelles magpie-robin on Fregate Island.
Native ants and humans have different ways of dealing with invasive ants. Native ants may use their own chemical weapons, physical defenses, or behavioral adaptations to resist or avoid the invaders.
For example, some native ants may produce repellent or toxic substances that deter or harm invasive ants.
Others may have spines, hairs, or armor that protect them from attacks.
Still others may change their activity patterns, nesting sites, or foraging strategies to reduce encounters with invasive ants.
However, these adaptations may not be enough to cope with the overwhelming numbers and aggressiveness of some invasive ants
Humans have developed various methods to control or eradicate invasive ants, depending on the scale and severity of the infestation.
These methods include mechanical removal, chemical pesticides, biological control agents, or integrated pest management (IPM).
Mechanical removal involves physically destroying or removing ant nests or colonies using tools such as shovels, vacuums, or steam generators.
Chemical pesticides involve applying toxic substances that kill or repel ants using baits, sprays, granules, or dust.
Biological control agents involve introducing natural enemies of invasive ants such as predators (e.g., phorid flies), parasites (e.g., microsporidia), or pathogens (e.g., fungi) that can reduce their populations or fitness.
IPM involves combining different methods in a coordinated and sustainable way that minimizes environmental and economic costs and maximizes effectiveness and efficiency.
