Introduction – Insect societies are well known for cooperation. However, there is a high potential for conflict both over resources (intercolonial) and over reproduction (intracolonial). Here I present the key results of my thesis in these two areas. 1. – In our first study we show that T. angustula possesses two types of entrance guards, hovering and standing guards, and that they have different tasks. Standing guards, however, can switch to hovering if needed. 2. – Honey bee, A. m. mellifera, guards recognise allospecific intruders via “different odours” not “harmful intruder odours”. 3. – Following up on project 1 we demonstrated a relatively clear division of labour in guarding of T. angustula where guards either act as standing or hovering guards. This study also adds descriptive data on the natural history at the nest entrances of T. angustula. 4. – In our fourth project we found that worker policing in the honey bee (A. m. mellifera and A. m. carnica) has a low cost because few recognition errors are made, 9.6% and 4.1% of eggs in male and female cells were removed in error, and because these errors are easily rectified. 5. – Virgin queens of M. quadrifasciata were only elected in queenless colonies and generally only shortly after the removal of the resident queen. The virgin queens' behaviour did affect their survival or their life time, respectively. Finally, we described the election process of virgin queens by their colony. Conclusion – Mainly the finding of two different entrance guards in T. angustula generated a series of new questions. In addition, this thesis helped clarifying how social insects recognise each other, it provided the first study that did not measure the benefit but the cost of worker policing, and it shed some light on the bizarre behaviour of queen replacement and execution in Melipona.