Beekeepers split their hives for various reasons, including to increase the number of colonies in their apiary, to reduce the size of a colony, or to stop swarm-related behaviors. To keep a hive from swarming, using a double-screen board (Snelgrove Board) is a good method. A Snelgrove Board has pairs of little shuttable doors on 3 of its four edges, and a central area with two layers of screen, which bees cannot pass through. Smells and warmth can pass through, but not bees. The upper and lower sets of doors allow you to siphon off flying foragers from the box above the Snelgrove Board into the colony below it. It all has to do with working with the foragers’ normal orienting behavior. The bees separate themselves into nurse bees above, who stay put, and foragers below.
The method described in this article is to be used on a strong colony early in spring BEFORE any queen cells have been made by the bees. You know when you have an amazingly populous colony coming out of winter and you sort of know they’re going to swarm? Try this method before they even get started on queen cells. This means in our area of upstate NY, do it in mid-April, well before dandelions start blooming. Louis Snelgrove described this technique in 1934 and it’s good for preventing a swarm by making a “vertical split.” You can choose if you want to actually make that split and increase your colony numbers, or not make it and reunite the bees, keeping the same number of colonies.
Read carefully and try doodling on a sheet of paper to understand which doors are being opened or shut as you read along. The goal is to separate foragers from nurse bees who will not abandon the brood, which prevents swarming. At the same time, you'll get some emergency queen cells started for the split — this happens separately from the queen’s space.
Starting the process: Day one
To start your split, follow these step-by-step directions to create a lower colony with the queen and a little brood, and an upper colony with a small amount of food and a lot of brood frames with nurse bees clinging to them:
- Remove all brood boxes from the bottom board and add an empty brood box on top of the bottom board.
- Examine the frames in the brood boxes and select a frame with some nectar, honey, and fresh pollen. Put it in the box on the bottom board.
- Select two frames of open brood with their clinging bees still attached, and the queen. These frames should have eggs and very young larvae. Inspect each frame very carefully to make sure there are no queen cells and, if there are queen cells, destroy them. Put these two brood frames with the queen in the center of the brood box on the bottom board and add frames that are mostly empty, to finish filling the box. These empty frames of comb (not foundation) give your queen ample room to lay eggs.
- Put a queen excluder over this single deep box and add supers, preferably supers of comb. If a super has only foundation, place that super just above the queen excluder.
- Put the Snelgrove Board on the top super. Orient it so the end without any little doors faces the same way as the hive’s normal entrance. Open an upper door on one side for the upstairs bees to use as an entry/exit.
- Place the second original brood box containing the rest of the colony on top of the Snelgrove Board. This box should have at least 3 full frames of honey/nectar, and brood in all the remaining frames. If there are too many brood frames to fit in this top brood box, give some brood to other weaker colonies to give them a boost. Close the hive up, and double-check to make sure you have one upper door open on one side for those upstairs bees to use. You’ll have an empty deep box to put away since you started with an extra one.
Continuing the process: Day six
Shut the upper door of the Snelgrove Board and open the one just below it leading to the lower colony. This means that bees that have matured into flying bees in the upstairs brood box will now enter at the same side but really be entering the bottom colony! This increases the forager force downstairs and helps fill the supers with nectar. Also, and very importantly, you must now give the upstairs bees a new entrance/exit on the opposite side by opening that upper door. Because of the screens between the upper and lower colonies, they all smell the same, so upper foragers will not seem like invaders when they enter below. Also, during cool weather, warmth is shared throughout the two parts of the hive. If you had made a normal split this early, one part might be at risk of becoming chilled.
What you have now is the lower colony with the queen but very few nurse bees, because the nurse bees were placed with most of the brood upstairs. Why won’t they swarm? Usually a swarm contains a queen and a huge amount of nurse bees. But what you have downstairs is a queen and a huge amount of foragers. Also, bonus: the whole foraging force of the original strong colony is filling supers with nectar because all foragers come to the lower colony. No bees were lost in a swarm. No bees were taken away for a split.
Upstairs, above the Snelgrove Board, the bees are pretty far from the queen below and feel queenless, so they’ve raised some queen cells from very young female larvae. This population upstairs will not swarm, because they have no queen. This upper colony can be taken off later to become a split, which will grow quickly.
Wait a minute! What if you don’t want another colony? You have two options here
Option #1: Allow queen cells to mature upstairs and a new queen will be laying on about day 30. At that point you could use a two-queen system, with supers in the middle area, one brood box below with the old queen and one brood box above with the new queen. But if that sounds too weird, just don’t let the queen cells upstairs develop fully. (Pick Option #2)
Option #2: Keeping just one colony with one queen, the old one. If this is your plan, then on day 7, search all brood frames in the upstairs colony carefully and destroy all queen cells you find. It’s best to shake the bees off the frames into their brood box in order to see every place a queen cell could be hidden. Cut all queen cells of any age or size. Continue on day 12 with the process of siphoning field bees off to the lower colony by changing the doors.
Day 12
By now it’s about the beginning of dandelion bloom. On day 12, you will again fool the upstairs foragers (newly matured in the past 7 days) into entering the downstairs colony, by shutting their little upper door on the side and opening the one just below it. Then give the upstairs bees a new entrance/exit at the back of the Snelgrove Board. If you let the queen cells upstairs develop, this back upper door is the one a new queen will use (maybe later today!) for her mating flights. As bees mature upstairs into foragers, they’ll also use this back upper door. Bees that had been entering at the side door will be confused for a day or so since no side doors are open now, but the large amount of scent coming from the wide front entrance at the bottom board will bring them down there and they will reorient.
Day 20
Continue siphoning newly matured foragers away from the upper colony and into the lower one. This is done by shutting the upper back door and opening the lower back door. Remember, you must now give the upstairs bees a new entrance/exit on the opposite side by opening that upper door. Also, at this time, the population in the lower colony will also increase even more because new bees raised down here since the original manipulation are emerging from their cells. Watch the supers carefully from now on and be ready to add another when they are filled with nectar or honey, 70% or more.
What to do next: Day 30
About four weeks after the split, you can inspect the upper part for signs of a newly mated laying queen — when egg-laying is confirmed, simply move the upper part to its own bottom board on another hive stand. Add an inner and outer cover and put away the Snelgrove Board. Tada! You have a new, small colony with a young mated queen. Watch this one carefully and give it another brood box or a queen excluder and a super in about a week. Add a honey super every 3 weeks or so.
But if you choose not to increase your numbers, this is what to do: After you see eggs being laid upstairs around day 30, replace the Snelgrove Board with a second queen excluder. This will give you a two-queen system, with supers in the middle area, one brood box below with the old queen and one brood box above with the new queen. All bees will work together and you can still decide later to do away with one queen. Or, you can leave them each in their own brood chambers and unite the two brood boxes when you take the supers for harvest. The queens and bees will work out which queen will live and which will die. But in the meantime, a two-queen system makes a lot of honey, and you have a backup queen if a friend needs one.
And your last step is to congratulate yourself for performing a swarm-stopping, massive nectar-collecting maneuver that’s effective but not often used! Get more tips and tricks in our Beekeeping Guide.
