Watching ants is as exciting as a thriller, believes Bernhard Seifert from the Senckenberg Museum für Naturkunde in Görlitz.

The entomologist has been researching hymenoptera for many decades.

Even as a child he enthusiastically watched them go about their activities, which fascinated so many people: how ants live in often gigantic yet efficiently organized states, milk aphids, carry loads or fight against other peoples.

A new trend has been evident for around ten years: Ant fans are bringing a colony into their living room, invasive species are also popular.

That can be dangerous.

Rebecca Hahn

Freelance writer in the science of the Frankfurter Allgemeine Sonntagszeitung.

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    You can quickly set up your own ant colony: You can easily order one or more queens and a few workers or larvae in one of the many online shops on the Internet.

    For Central European ants you only have to pay a few euros, for more exotic imports the prices move from around thirty euros upwards.

    They are sent in test tubes, usually within a few days, in the normal way by post.

    Then the crawfish should move to a formicarium, a special terrarium for keeping ants, with which their owners can keep an eye on how they are laying out corridors, transporting food and disposing of waste.

    Crawling animals in the luggage

    Two researchers from the University of Lausanne have investigated which species of ants are traded on the Internet. They reported in April in the journal

    PNAS

    that invasive species are sold disproportionately often

    . "We have now discovered over 600 species of ants that are offered on the Internet," says Cleo Bertelsmeier, author of the study alongside Jérôme Gippet. These include 14 of the 19 most conquering species in the world. If these continue to be sent around the globe, invasive species could spread more widely, the researchers fear.

    Over 15,000 different species of ants are known worldwide.

    Even without the animal trade, some have managed to settle far beyond their traditional range, mostly hidden in people's luggage.

    "The passive transport by humans is the main factor that foreign ant species enter an area," says Bernhard Seifert.

    The insects would often be transported in plant pots, for example.

    Other species are so small that they can even hide in a laptop keyboard.

    Branch nests are quickly established

    Black head ants, for example, have spread almost worldwide as stowaways. Thanks to their short body length of barely two millimeters and the milky, almost transparent abdomen, the workers of

    Tapinoma melanocephalum are

    easy to overlook. The species is now widespread in all countries of the tropics and subtropics, where it occurs both indoors and outdoors. At least in greenhouses and heated buildings, black head ants can now also be found in temperate latitudes, including Japan, Europe and North America.

    Once the animals have got used to it, the colony grows in no time at all.

    A hundred to a thousand ants live in a single nest.

    If the space becomes too small, branch nests form with which the colony spreads further.

    Blackhead ants are very flexible in their choice of food.

    In the household they prefer to satisfy their appetite with sweet foods, outside or in greenhouses they tend to have aphids to collect their honeydew excretions.

    "Very active" rating

    The World Conservation Union counts blackhead ants among the extremely invasive ant species. Dealers still offer them for sale. They even advertise online the properties that make blackhead ants so invasive: The species is "very robust" and "extremely active", and the strong colony growth is also emphasized. No mention is made of the fact that it is an invasive species. At most, the sellers point out that the tank must be thoroughly sealed so that the tiny insects do not escape.