It is essential that there is plentiful supply of drones with a good genetic pedigree present in each colony. This will ensure that any new queen is mated successfully.
The use of the frame shown below has been used very successfully to this end.
Drone brood and queen mating
The first drone brood appear in the colony in mid April. From the laying of the egg the drone is ready for queen mating after 37 days. So the earliest that queen mating can take place is towards the end of May.
A virgin queen is ready for mating 21 days/3 weeks after the egg is first laid. For mating to coincide with the appearance of mature drones, it follows that queen breeding (the production of queen cells) should not start until say the second week in May.
After mating a further 2 weeks (until mid June) is required for the new queen to be assessed from the
new brood she produces.
So much for theory, in practice so much depends on the weather and the willingness of the bees to produce queen cells early in the season.

Drone characteristics
After emerging drones continue to be fed by the nurse bees. After 8 days the drones are able to feed themselves and fly from the hive; but are only able to fertilize the queen after they are 13 days old.
Drones are mainly seen flying only in fine weather in the afternoon; 30 minutes is about the average length of each flight.
Drones have a high energy requirement and therefore return frequently to the apiary where they visit any hive to top up their joules.
Although a drone can fly many a mile, queen mating often takes place within the vicinity of the apiary. I feel sure that the drones know when a virgin is present in a colony; the hive being visited by a host of drones.
On mating, of course, the successful drone dies and the queen returns to her colony with the mating sign.
Drone genetics
The drone carries only one set of chromosomes from its mother. If, therefore, this queen has undesirable characteristics which are not to be passed on when new queens are mated in the apiary, then the drones which she produces can be trapped using the frame shown below and so destroyed. The colony can later be requeened.
On the other hand if drones of the right strain are present, then it is essential to ensure that sufficient numbers of these are present so as to flood the apiary.
Drone genetics is discussed in more detail in
Genetics 2C.