They provide a variety of services, from foraging for food and feeding nestmates to removing waste from the nest and expanding the nest through excavation. Once a raid is complete and the host brood have been acquired, the newly-acquired ants become the housekeepers of the colony when they develop into adults. But not all species are quite as deadly: Harpagoxenus americanus will kill very few host adults and will simply take the brood back to their nest. These raids might seem aggressive, however some species, such as Leptothorax duloticus’s, are especially brutal as they kill most of the adult workers upon invasion and sometimes take over the nest as their own. Some raiders stand guard at the raided nest’s entrance to prevent any brood from escaping with a host worker. An assembled party will then head to the host colony where it will kidnap the brood to bring back to their own nest. Once an unfortunate and unsuspecting host colony is found, the scouts return to their own nest to form a raiding party. An individual slave-making worker or a small group of slave-making workers will head out of the colony as scouts to find a new host colony. What about the workers? Once the queen has given rise to a suitably-sized colony with workers of her own species, the raids begin.
So far, we’ve only discussed the queen’s invasion into a host colony. A Polyergus mexicanus parasitic queen (in red) with her Formica argentea host worker (in black). With the help of these manipulated host workers, the queen can grow her colony with workers of her own species. This can be done by grooming herself near the injured or dead host queen or by rolling around and covering herself in the nest debris. One way that Polyergus queens manipulate the host workers is by acquiring the scent of their original host queen. The parasitic queen manipulates the host ants to engage in cooperative behavior towards her that normally would have been reserved for fellow colony members. How does she get this support, you may ask? Workers can usually identify whether or not other worker ants are part of their colony however, slave-making queens can disrupt this recognition process. Now that she has the support of the host workers, they can rear her own brood. All of this in a day’s work? No thank you! The reason this queen flies solo in her attack is because she requires workers to help care for her brood. The queen, who has already mated with a male, must invade the colony, usurp the host queen either by killing her or driving her away, secure the host’s brood, and have the host workers accept her as their own queen. Otherwise, a solo queen will invade a host colony alone. If the queen already has adult workers of her own species, the workers will invade the host nest. The occurrence of either invasion is dependent on the size of the queen’s colony. The parasitic process of dulosis can be characterized by two types of invasions into the host colony: invasion by slave workers and invasion by the parasitic queen. Slave-maker Polyergus mexicanus ants and their hosts Formica argentea together in one colony. The number of host workers within a colony can range from a few dozen to several thousand. Amongst these various genera, parasitic species differ from each other in colony size, with or without the kidnapped host workers. In the Myrmicinae subfamily, species such as Leptothorax duloticus, Harpagoxenus americanus, and Temnothorax americanus, which used to be known as Protomognathus americanus, engage in slave-making activity. Some slave-making ant species in the Formicinae subfamily include Polyergus mexicanus, Raptiformica sanguinea, and Rossomyrmex minuchae. Most parasitic ant colonies are found within two subfamilies of ant species: Formicinae and Myrmicinae. It involves the co-existence of two ant species within a single colony through the kidnapping and rearing of the host colony’s brood by the parasitic colony’s workers, otherwise known as dulosis. Only about 50 out of over 10,000 ant species practice this form of social parasitism. In fact, kidnapping and, for lack of a better term, enslavement is essentially what these ant species do best. “Take no prisoners!” said no slave-making ant ever.
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