Congratulations if your bees survived the winter. The main honey flow will be upon us in several weeks. To obtain a good honey crop, a honey bee colony must have many bees (about 50, 000). However, a populous colony is also more likely to swarm, leaving you with little or no surplus honey.
Swarming is colony reproduction; all organisms have the urge to reproduce. For a honey bee colony, making more workers is not reproduction. To reproduce, they need to make a new queen; then the colony divides, with one portion getting the old queen and the other having the new queen. This division process is call swarming.
We don’t completely understand the factors that initiate swarming, but crowding of the brood nest and less queen pheromone certainly contribute to the swarming process. Thus, to mitigate swarming, prevent crowding of the brood nest. A simple procedure is to insert frames of drawn comb into the brood nest (foundation also helps, but use less). Caution: do not insert frames if cold weather is predicted. If the bees cannot maintain 93o F over the entire brood area, brood will chill and die. Repeating this procedure may prevent the development of the swarm urge.
However, many times the bees will decide to swarm despite our best efforts. A queen cup is the beginning of a queen cell usually along the bottom of the comb. An empty queen cup does not indicate swarming will occur. However, once there is an egg or larvae in what was formally a queen cup, it becomes a queen cell, indicating that the colony will swarm. A queen develops more rapidly than a worker, taking only about 16 days to develop from an egg. The egg hatches 3 days after laying, the larvae is fed copiously for 4 days and the queen cell is capped at about 8 days. The prime swarm (one with the old queen) usually departs at about 8 days. Once a queen cell is discovered the colony will swarm in 4 days or less (depending upon the age of the larvae and weather conditions). There are several procedures that usually (but not always) prevent swarming as detailed in the links below. Pick a procedure and bee prepared.
During swarming season (mid-April through May), I suggest that you check your colony for swarm preparation every 7 days. Controlling and preventing swarming, requires a lot of time and effort, but your work will reward you with a large honey crop.
General Information http://www.dave-cushman.net/bee/swarmcontrol.html
Pagden method http://barnsleybeekeepers.org.uk/pagden.html
Snelgrove method http://barnsleybeekeepers.org.uk/snelgrove.html
Demaree method http://barnsleybeekeepers.org.uk/demaree.html