Argentine ant

Argentine ant ( Linepithema humile ), museum specimen

The Argentine ant ( Linepithema humile ) is a type of the glands of ants ( Dolichoderinae ). She is originally from South America, but it was accidentally kidnapped by people in new areas and has now become an almost worldwide spread, invasive neozoon.

Features

The Argentine ant is light brown. Workers are 2.1-3 mm long, queens reach a length of 4.5-4.9 mm.

While the genus Linepithema is well recognized that members of the genus with each other are difficult to distinguish. Other Linepithema species are very often confused with the Argentine ant. In Central Europe, the workers are to be distinguished by a number of characteristic features of other glands of ants. The propodeum dominates the mesonotum significantly. The dentition of the mandibles is built very irregular: In total, there are 5-6 distributed over the Kaurand larger teeth and in the gaps 11-15 significantly smaller teeth. The lower jaw switches are 6 -membered, 4 -membered the Labialtaster.

Dissemination

The original area of ​​distribution of the Argentine ant was limited to Argentina, Brazil, Paraguay and Uruguay, where it occurs near the Río Paraná. Today, the Argentine ant is a nearly worldwide spread neozoon that was accidentally deported with the transport of goods as on ships and planes. Currently ( 2011) it has expanded its distribution to a total of 21 countries on several continents. In 1895 she was first deported to southern Europe and spread from large coastal cities, starting especially in anthropogenic habitats from. Since the nature but this is not frost-hardy, their range in Central Europe has so far been limited to hot houses - there are no permanent field presence. This species was previously often delayed in their propagation by climatic constraints, therefore global warming could favor the spread of this invasive species. Local also slow domestic, competitive strong ant species the spread of the Argentine ant.

Ecology

The habitat of the Argentine ant in their original home is tropical and subtropical forest. Their preferred habitats in Europe are agricultural areas, gardens and various other, influenced by man habitats. However, it also penetrates into non- disturbed habitats, including oak and pine forests in the Mediterranean. They preferred areas with moderate temperature and humidity. Argentine ants are omnivorous and take honeydew, nectar, insects and carrion itself.

Colony structure

In their home colonies of the Argentine ant monogynous ( one queen per colony), and the colonies fight each other. There, where it was introduced, the Argentine ant, however, form so-called super colonies of several nests ( polydom ), each with multiple queens ( polygynous ). These colonies can extend over enormous areas: the largest extended after the 2007 level over a length of 6000 km from Galicia to Italy. Reason is the so-called founder effect: Usually only very few individuals are abducted and therefore very little genetic diversity. Of these genes are also affected, involved in the production of so-called cuticular hydrocarbons. Based on these chemical signature seen ants members of their own colony and can distinguish them from other colonies. However, since trains initially only a few individuals an entire population, the entire population has similar equipment for the detection of colony members - they are not aggressive to each other.

Hatching queens are mated directly in the nest. For their average lifespan of 0.9 years, they then produce eggs. In the absence of queens workers can lay unfertilized eggs which then hatch males. The super wide colonies reproduce by conditioning of new nests in the vicinity of old nests and expand at an annual rate of up to 150 m.

As an invasive species

The Argentine ant is classified worldwide by the Invasive Species Specialist Group of the IUCN as one of the 100 worst invasive species. Even though they usually settles in areas dominated by humans, so they can also penetrate into natural habitats. There it often occurs as a superior competitor of native ants, because they do not fight each other by their super colonies and can optimize the search for food. Often they find food faster than other ants and show partly aggressive behavior towards local ant species. Because of the extremely high stocking densities, which can reach as super colonies, they are directed to also considerable damage to ecosystems as a whole - as they interfere by reducing native ant mutualistic relationships between native ants and plants. Due to intensive hunting they can reduce stocks of native arthropods strong, some of which are important pollinators of plants. To take flowering plants indirectly damage. Last can also damage agriculture go hand in hand, as Argentine ants, like many other ants cultivate aphids to get to honeydew. Due to the large number of Argentine ants stock explosions of aphids can be caused, which then damage crops.

Because of these problems has been repeatedly tried to exterminate the Argentine ant locally, mostly without success. Various measures to prevent introduction and insecticides are used. In California, for example, stocks of the Argentine ant could be locally reduced by up to 90 % by poisoned baits were designed.

Scientists from the University of California, Irvine have developed a method for the smell of the Argentine ant to use against them. The individual hydrocarbons profile of the exoskeleton of ants plays an important role for the detection of other members of the nest. The scientists developed a substance of natural similar, but is different therefrom. This material performs when applied to an individual means that other members of a colony nest attack and kill this individual. This chemical control method could, in combination with other treatments to effectively combat.

Another approach for large-scale control of the Argentine ant has been proposed by scientists from Japan. They showed that it is possible to affect the Wegfindungsverhalten the Argentine ant using a synthetic pheromone .. This was later confirmed by further experiments a New Zealand research group in Hawaii and was undertaken by the Victoria University of Wellington, which showed that this approach is also positive impact on other local ant species has ..

Film

• War of ants. Television documentary, Germany, 2012, 52 min, written and directed by Stefan Geier, production: Arte, Bayerischer Rundfunk, first broadcast on September 6, 2012 in arte, Summary of arte. Documentation on the largest colony of Argentine ants Super along the southern Mediterranean coast. The film shows what strategies combat the Argentine ants native species and supports scientists who want to stop their spread.