EN
Formica sanguined Latr. occasionally takes wood ants as its slaves. Eleven nests of the former were experimentally provided with various amounts (10,000-250,000) of pupae of F. polyctena Foerst. or F. rufa L., and thus, mixed colonies with different proportions of slaves (29-96%) were obtained. The slaves destroyed the F. sanguinea colonies by eliminating their brood andqueen(s) (with no aggressiveness towards adult workers). The following year, even though F. sanguinea workers were still present, the slaves adopted young queens of their own species. Before their complete emancipation, the slaves fought on the side of the slavers during conflicts with conspecific ants, even against their former nestmates. Emancipation restored mutual comity between the ex-slaves and the unenslaved F. polyctena. At the same time, the ex-slavers lost their aggressiveness towards alien F. polyctena (but not vice versa). The mixed colonies were raided by foreign F. sanguinea. The studies were carried out in the Gorce Mts (the Western Carpathians) from 1987 to 1991.