It is important to understand the purpose of a queen excluder and how it works. If used inappropriately it can be damaging for the honey bee colony. All beekeepers using queen excluders must have a good understanding of the structure of the honey bee brood nest.
- The brood nest always maintains the same basic structure. It is not a random structure - the thermoregulatory demands of keeping the brood nest at the constant 35C temperature, that is needed for successful brood rearing, demand otherwise. The brood nest is always maintained as a ball shape that is sliced through with parallel honeycombs. The largest part of the brood nest is in the centre. This is where the queen will start laying with the nest expanding outwards from the centre as the colony expands after the dearth period. Surrounding the brood nest, placed to be convenient for feeding the young brood is a ring of the proteinaceous pollen required for larval growth. Surrounding the pollen ring will be a ring of honey. The surplus honey will be stored around the brood in a manner that is determined by the shape of the containers in which the bees are nesting (e.g. hollow tree or beehive). In a frame hive, with the honey storage placed above the brood nest the honey will be stored on top of the brood; in a long hive, such as a fixed comb hive or a top bar hive, the honey will be stored behind the brood. In either case the size of the brood nest will stop growing in size as it reaches the point where enough foragers have been produced for the main nectar flow. After this point the bees will store honey only, and the queen will not venture further to lay eggs. This can make harvesting very easy in well designed top-bar hives or in fixed comb hive as honey only needs to be removed until the first brood comb is reached. After that there will be no more honey, only increasing amounts of brood. Brood should not be harvested.
- It is important to realise that the placing of the honey in relation to the brood nest is directly affected by the position of the entrance of the beehive and this is particularly relevant for long hives where the position of the entrance is a matter of choice. The bees will always place their brood close to the entrance with the honey stores further away from the entrance. Hives with an entrance at the end will consequently have brood at one end and honey at another. Hives with an entrance in the middle will have brood in the centre and honey on either side. This design does not give such a convenient harvesting arrangement, especially in top-bar or fixed comb hives.
The queen excluder is a piece of preformed metal or plastic that is placed between the brood and the main honey storage areas of the beehive. The intention is to constrain the queen's egg laying into one area while workers are able to push through a slotted piece of metal to store the honey in another area of the hive. They are used in frame hives because the arrangement of the beehive is modular and the modular sections are placed one on top of the other to form a high tower arrangement, which can sometimes allow a long thin vertical type of brood nest. But mainly they are used because it is has been done for a long time in the developed world and no one has questioned the value of this piece of equipment.
However, there are a number of problems inherent in the use of queen excluders. Increasingly people are finding, even using frame hive systems, that queen excluders are damaging to the bees for a number of reasons and are starting to question if it is necessary to use them.
- They damage the body of the worker bees each time they have to push through. The bees' legs and wings suffer damage, pollen is knocked from their legs and hairs from their body. The very sharp wire mesh sometimes used in countries where technical equipment suppliers are absent (e.g. Malawi, Uganda) is viciously damaging to the bees bodies and reduce both their life span and their productivity.
- Queen excluders reduce the ventilation flow of air through the hive especially if they get blocked with wax and propolis as they frequently do. This in turn will affect the propensity of the bees to swarm. This may be a critical factor in tropical beekeeping where the colonies are much more likely to swarm and to swarm more frequently than temperate bees. The consequence of this is that they store less food and are therefore less productive for the beekeeper if there is a great deal of swarming.
- Queen excluders limit the egg laying capacity of the queen to the space allowed by the beekeeper. Thoughtful beekeepers in developed countries are starting to wonder if the colony is best left to choose for itself how much brood it wishes to make. The brood of course grows into the foraging work force. Consequently the more bees there are available for foraging the more nectar can potentially be collected. The colony 'knows' the correct size of brood needed to support its life activities and of course this will change dynamically throughout the year according to the seasonal development pattern of the colony. If the beekeeper constrains this artificially then the colony may be reduced in its potential size and therefore its productivity.
- It is inevitable that at times a queen will get through the queen excluder into the honey storage area. This happens frequently with frame hives. This causes abandonment of the brood nest over time and the hive area gets smaller unless the beekeeper corrects the position. Because the frame hive system is modular then it is easy to do this. However, if queen excluders are used in other hives types it is not always as easy to correct the situation.
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