Swarm controls will have resulted in an increase in numbers. Getting back to the number you thought of first is simple: put two colonies together, but do it carefully.
The accepted way to unite two colonies is using a sheet of newspaper. The books will tell you to move the colonies close together, moving one of them a yard at a time each day, but my experience is that this is unnecessary. Simply wait until the bees have stopped flying in the evening, remove the crown board from one hive and lay a sheet of newspaper directly over all the frames of the brood box, (use a broadsheet not a tabloid) then place the second colony over the top of the newspaper. You can make a few small holes in the paper but I never do. Close up and leave for a week before inspecting and reassembling into one unit.
If there are supers, ensure that there is a sheet of newspaper wherever adjacent boxes contain different bees.
A few precautions:
- loosen all hive parts and take any brace comb off the bottom of the frames of the top box beforehand, preferably earlier in the day.
- At the same time remove the queen you do not wish to keep.
- Put a queen excluder on top of the newspaper so that the queen is confined in one box and also to hold down the newspaper.
- I find a fine water spray will keep the bees in the bottom box immobilised for the short time they are exposed.
(Celia F Davis, Warwickshire BKA)