When the queen lays honey bee eggs, up to 2,000 a day, she first backs into a cell and measures it. If the cell is the smaller size she fertilizes it as she lays it. I’d rather not get drawn into one of those ‘which came first, questions. In the larger cells she lays, but does not fertilize it. The size of the cells built by worker bees depends on whether drones or workers are required.
Usually there is only a small percentage of drones in a colony. The overall majority of bees are workers. Whether fertilized or not, it hatches and the larvae emerges in about 3 days.
One of the big questions for a beekeeper, when he inspects a colony, is whether the queen is still in residence, and is still laying. In a colony of 60,000 or more bees it’s often difficult to find the queen. Instead the beekeeper will look to see if there are fresh bee eggs. If the tiny, upstanding ‘white whiskers’ are found, then it can be assumed that the queen was at least present in the last day or two.
Those which are fertilized will become female bees, mostly workers but possibly a queen, any which are unfertilized become males bees, called drones.
If something happens to the queen, the workers make a last ditch attempt to pass on the colony’s genes. Some of the infertile workers begin to lay unfertilized eggs, unlike the queen these laying workers put more than one in each cell. These develop into drones, although the hive cannot continue, the drones can at least mate with a queen from another hive, thus passing on their genes.