Queen Excluders

Queen excluders are perforated or wire sheets placed inside the hive between the brood box and the honey super, or between compartments, that let worker bees through but stop the queen and the drones. There are different types, wire, plastic and perforated sheet; the gap size, frame construction and how it sits on the hive determine whether an excluder works or not. This page deals with the excluder as a hive part: its types, dimensions, fitting and maintenance.

How does a queen excluder work?

An excluder is a "size filter". It makes use of the difference in body thickness between workers, the queen and drones:

• The worker bee can pass through the gaps in the excluder; foragers carry honey up, and nurse bees move between the two sides.
• The queen cannot pass because of her thicker thorax and abdomen; laying stays below the excluder.
• The drone cannot pass because it is the largest of all; for this reason an exit should be provided for drones left above the excluder.

Although old texts sometimes describe it the other way round, this is correct: the excluder lets workers through and stops the queen and drones. On standard excluders the gap is usually around 4.1–4.4 mm. The narrower the gap, the harder it is even for workers; the wider it is, the greater the risk of a small queen getting through.

What types of queen excluder are there?

Wire excluder

Made by welding parallel round wires to cross strips; it is often set in a wooden frame.

• Because the wire has a round cross-section, it wears the bees' wings and hairs less and passage is easier.
• It is sturdy, can be cleaned with a blowtorch or hot water, and lasts a long time.
• Framed types have a bee space on one side; this stops the excluder sticking to the top bars and lets the bees use the whole surface of the excluder.

Plastic excluder

Light sheets with long slots, moulded in one piece.

• Cheap and light, easily cut to fit the hive.
• Bends over time and can warp in the sun and in hot water; a warped excluder leaves gaps at the edges.
• Poor-quality ones may have rough edges on the slots; when buying, check that the edges are smooth.
• Cannot be cleaned with a blowtorch; it is cleaned by chilling it and scraping off the propolis once it becomes brittle.

Perforated sheet excluder

Made by punching long slots in a metal sheet. It is sturdy, but if the slot edges are sharp they wear the bees; thin sheet bends easily. Today wire and plastic types are more common.

Special excluders

• Vertical dividing excluder: Placed upright between frames inside the hive; used to confine the queen to a few frames.
• Excluder cages and compartments: Cage-type devices used to confine the queen to one or two frames for a short time.
• Entrance excluder: Fitted to the entrance; it stops the queen leaving. It is not reliable on its own for preventing swarming and also blocks drones from leaving; it should be used carefully and for short periods.

What should you look for when choosing an excluder?

• Size fit: The excluder must cover the top of the hive completely, with no gaps at the edges. Langstroth and Dadant sizes are different.
• Even gaps: The wires must be evenly spaced and parallel; even a single widened gap can let the queen through.
• Bee space: On framed excluders, pay attention to which side the bee space is on.

How is a queen excluder fitted to the hive?

1. Inspect the brood box; see the queen, or at least make sure there are no eggs or young larvae on the frames you are going to move up.
2. Scrape excess comb and propolis bridges off the top bars with a hive tool; the excluder must sit flat.
3. Place the excluder flat. With wire excluders, it is often recommended that the wires run at right angles to the frames; if the manufacturer specifies a direction, follow it. Which side of a framed excluder the bee space should face depends on your hive's construction: about 6–9 mm of bee space should remain below and above the excluder, as more than that leads to brace comb.
4. Feel with your finger that there are no gaps at the corners and edges.
5. Put the honey super on top; in the first super, giving one or two drawn combs directly above the excluder speeds up the bees' passage.
6. A week later, check the super for eggs: if there are eggs, the queen has stayed above.

Maintaining and cleaning a queen excluder

The excluder's worst enemies are propolis and wax. As the gaps narrow, passage becomes harder and the bees start to treat the excluder like a wall.

• Clean it in the cold: Propolis becomes brittle in the cold. Leaving a plastic excluder in a deep freezer for a while and then flexing or brushing it makes cleaning easier.
• Wire and metal excluders: Scrape with a hive tool; remaining wax and propolis are removed with hot water or brief heating with a blowtorch. The wires must not be overheated and bent.
• Checking: After cleaning, examine the gaps against the light; if there is a spread wire or a broken slot, replace the excluder.
• Storage: Store on a flat surface, with no weight on top and out of the sun; plastic excluders bend in the heat.
• Hygiene: An excluder from a diseased hive is not fitted to another hive until it has been cleaned and disinfected; for notifiable diseases, official instructions are followed.

Common mistakes

• Seating the excluder crooked or upside down; the queen gets past at the edge, or the bee space is lost.
• Cutting and patching an excluder to fit a hive of a different size on the assumption that "it'll do".
• Using a clogged excluder for years without cleaning it.
• Going into winter with the excluder on; the queen can be left separated from the cluster.
• Forgetting an entrance excluder for a long time; drones build up inside and the entrance gets blocked.