Over time

Ordered to expand, the colony expands the nest's capacity.
Ordered to breed the colony do so if there is enough capacity.
If the food level (r_workers * r_food) is above 40% the food increases. If lower it decreases and when out of food, ants start dying. NOTE: This is one way to kill your colony.
If the number of ants in the colony is bigger than the nest capacity limit, the number of ant is slowly decreased
Slowly migrating actual Worker and Warrior amount towards the setting (ants are given new tasks)
Sometimes cave ins and other accidents occur (decreasing capacity and killing ants)
See Technical Implementation for the actual calculations being done