A Snelgrove board is a specialised division board inserted between two brood boxes. Instead of a single entrance, it gives the beekeeper independent, closable entrances at the front and back, at both the lower-box level and the upper-box level. By opening and closing these in a planned sequence over roughly two weeks, a beekeeper can split a colony's queen-right box from a queenless, cell-raising box on top — without losing any of the colony's flying foraging force to a swarm.
The method is named after L. E. Snelgrove, who described it in his 1934 book Swarming, Its Control and Prevention. Because it keeps the whole flying force working while splitting queen from queen cells, it is prized by beekeepers who want to raise a new queen or prevent swarming without sacrificing a honey crop.
A cutaway two-box hive with a Snelgrove board between them: four independent, closable entrances let a beekeeper redirect returning foragers between the queen-right box and the queenless, cell-raising box on top, without ever losing flying bees to a swarm.
Foragers always try to land at the original entrance location. By opening or closing the front-lower versus front-upper door, that same stream of returning bees can be steered into either brood box, conserving the colony's total foraging strength.
Pick a manipulation-timeline stage or toggle the four entrance buttons yourself, adjust forager traffic, and watch where the amber bee stream ends up — plus how the swarm-impulse gauge responds to congestion at closed doors.
Because the method never actually loses bees — only redirects them — a colony treated with a Snelgrove board can still produce a full honey crop even while its swarming urge is being broken.