Food - honey storage. If there is less then 10 kg of food in the hive, the queen will cease laying eggs.
In our environment carnica colony normally needs apr. 20 kgs of well prepared food (overwintering + build up). Carnica always stores food right next to the brood and they use the food very rationally. The problems can be caused during the build up period if not managed correctly, even for the wintering that is more than excellent.