A queen excluder is a foundational piece of equipment in managed beekeeping, designed to organize the internal structure of a honeybee colony. Its primary function is to serve as a selective barrier, ensuring the queen bee remains confined to a specific area of the hive. By controlling where the queen travels, beekeepers maintain a distinct separation between the brood nest and the honey storage areas. This tool allows for a more efficient and cleaner honey harvest by preventing the queen from laying eggs in the sections intended for surplus honey.
Physical Design and Primary Function
The effectiveness of the queen excluder relies entirely on a precise measurement that exploits the natural size difference between the various castes of honeybees. The barrier is constructed with openings that are carefully sized to allow the smaller worker bees to pass through unimpeded. These openings are typically limited to a width of approximately 0.163 inches (4.1 millimeters), though some variations may be slightly wider, up to 4.4 millimeters.
The queen bee, having a significantly larger thorax than her worker offspring, is physically unable to squeeze through this narrow gap. Similarly, the male drones are also too large to pass the barrier, often becoming trapped if they wander above it. This design ensures that the queen is restricted to the lower boxes of the hive, known as the brood chamber, where she can continue her egg-laying duties.
The fundamental purpose of this confinement is to keep the upper sections, called honey supers, free of eggs, larvae, and pupae. If the queen were to lay eggs in the honey frames, the resulting brood would complicate the honey extraction process and contaminate the final product. By keeping the honey supers brood-free, the excluder guarantees that the harvested comb contains only pure honey.
Placement and Seasonal Application
Proper placement of the queen excluder is necessary for it to function as an effective management tool. In a standard hive setup, the excluder is positioned directly on top of the uppermost box designated for the brood nest. This structure creates a physical division between the lower brood area and the honey supers that are stacked above it. Before adding the excluder, beekeepers must confirm that the queen is located in the lower brood box, as accidentally trapping her above the barrier can be detrimental to the colony.
The timing for placing the excluder is tied to the condition of the colony and the environment. Beekeepers typically install the excluder when the colony is strong and a significant nectar flow is beginning, which is usually when the first honey super is added for the season. A strong hive is required because the barrier can create a slight bottleneck, and a weak colony may struggle with the restricted traffic flow.
Conversely, the excluder must be removed later in the year, typically following the final honey harvest in late summer or early fall. Removing the barrier allows the colony to move freely as a cohesive unit in preparation for the colder months. If the excluder is left in place during winter, the queen may be separated from the main winter cluster of bees, leading to her death from exposure and the subsequent loss of the colony.
Types and Management Considerations
Queen excluders are available in a few different physical forms, primarily distinguished by their construction material and style. The most common varieties are made from either a metal wire grid or a molded plastic sheet.
Material Differences
- Metal excluders, often framed in wood for stability, are durable and easier to clean with heat, though some designs may impede airflow.
- Plastic versions are lighter and more affordable but can be prone to warping in high temperatures and generally have a shorter lifespan.
Beekeepers consider the practical trade-offs associated with using the excluder, which can influence colony dynamics. One common issue is drone congestion, where the larger male bees become trapped in the honey supers above the excluder since they cannot pass back down into the brood area. This can lead to the excluder becoming clogged, reducing the efficiency of worker bee traffic.
The barrier may also slightly slow down the movement of worker bees as they navigate the narrow openings, potentially reducing the rate of honey storage during a heavy nectar flow. Careful monitoring is necessary to ensure the excluder is clean of propolis and wax buildup, which can further impede the workers’ ability to pass. Younger or smaller queens may occasionally be able to slip through the openings, requiring the beekeeper to remain vigilant during inspections.