Rossomyrmex minuchae has a remarkable life history. Unlike other ant species, in which the worker ants (wingless, sterile females) undertake tasks such as searching for food and defending the nest, worker Rossomyrmex minuchae ants enslave another ant species to do this work instead (3) (7). Proformica longiseta, another ant endemic to the mountains of southern Spain, is the unfortunate species that is enslaved by Rossomyrmex minuchae (8).
Rossomyrmex minuchaeis only active outside of its nest for two months each year, between late June and early August. During this period, Rossomyrmex minuchae workers first scout for a nest of Proformica longiseta; once found, around 60 to 90 Rossomyrmex minuchae gather by the target nest and the invasion begins, with some ants invading through the main entrance while others dig into the nest. A struggle between the two ant species is presumed to take place within the nest, and results in Rossomyrmex minuchae carrying Proformica longiseta pupae, larvae, eggs and small workers back to their own nest. When the pupae hatch, they accept the Rossomyrmex minuchae nest as their own and forage for Rossomyrmex minuchae and care for its brood (3) (6) (7).
All reproductive activity of Rossomyrmex minuchae also takes place within this very short period of annual activity, typically for three weeks during July and August. The mating strategy of this species is characterised by two activity periods. During the ‘mating period’, females call in order to attract males, mate, then return to the nest in which they were born. During the ‘dispersal period’, mated females fly from the nest in search of a new non-parasitized Proformica longiseta nest (8), where they eliminate and replace the Proformica longiseta queen. In this parasitized nest, the Proformica longiseta workers care for the slave-maker (Rossomyrmex minuchae) brood and perform other nest duties, while the slave-making workers specialise in raiding new nests to refresh the worker force (9) (10).