In queen rearing, grids are used to separate parts of a colony without separating the bees.

The principle

A queen excluder lets workers through but stops the queen. This creates a part of the colony that behaves as if queenless while the bees move freely back and forth.

That is exactly what a cell builder needs: the urge to feed cells, but with a queen keeping the colony going.

Working partly queenright

• The queen stays in the lower box, behind the excluder
• The rearing frame hangs above it
• The bees above the excluder have no direct queen contact and draw cells
• The colony does not weaken, because brood rearing continues

This is more sustainable than keeping a colony fully queenless, which becomes exhausted.

Where else it is used

• When making a nuc: To prevent the queen going along
• When introducing: To keep the colony partly queenless and improve acceptance
• In royal jelly production: Working continuously without the colony collapsing
• On the floor during transport, so the queen cannot leave

Material

As with ordinary excluders: wire grids with round wires give smoother passage than plastic grids with sharp edges, which wear the wing margins.

Practical points

• Lay flat; a warped grid leaves gaps the queen passes through
• Check where the queen is before fitting the grid
• Scrape off propolis; a propolised grid lets nothing through

What it does not solve

A grid does not make a weak colony strong. A cell builder must be full, rich in young bees and well fed — the grid only controls where the queen is.