• Behaviour;
  • caste;
  • dependent colony foundation;
  • emigration;
  • ergatoid queen;
  • Mystrium oberthueri;
  • nest relocation;
  • polygyny
  1. Nest emigrations are perilous for social insect colonies. Outside their nests, adults and brood are exposed to dangers. The behavioural mechanisms of emigration are thus likely to be under strong selective pressures.
  2. Most studies on emigration have focused on monogynous species where survival of the queen is paramount, but emigration processes are largely unknown for species having several queens per colony.
  3. In colonies of Mystrium oberthueri Forel, members of the morphological queen caste are as numerous as workers, although only a few of them mate and reproduce (polygyny). All queens perform intranidal tasks, such as brood care. Accordingly, we expected them to participate actively in emigration and to be less well protected.
  4. Using four colonies, we studied the dynamics of 16 emigrations with a special focus on individual behavioural profile.
  5. Workers were more involved than non-reproductive queens in recruitment and brood transport. Reproductive queens and young ants preferentially walked directly to the new nest without carrying brood. A chemical trail was probably used. The physiological status of individuals had more impact on their behavioural profile than their morphological caste.
  6. This highly organized emigration process may underpin dependent colony foundation, as both involve the coordinated movement of nestmates.