Cell Holding Cabinets

A queen cell incubator (queen incubator, incubation cabinet) is a thermostat-controlled cabinet that keeps sealed, ripe queen cells outside the hive at a stable temperature close to that of the brood nest and at suitable humidity. It gives flexibility on distribution day and makes it easier to transport queen cells and collect virgin queens; but a temperature deviation or a power cut can kill the whole batch at once. This page explains when an incubator is needed, the correct settings, how to choose one, and how to use and maintain it.

What is a queen incubator used for?

Ripe queen cells are normally distributed to mating nuclei on day 10 after grafting; the queens emerge on days 11–12. If distribution is delayed because of weather, workload or box preparation, the first queen to emerge kills the other cells. An incubator removes this danger by keeping the cells outside the hive in separate individual compartments, and allows distribution to be postponed by one or two days.

• Distribution flexibility: Cells are given to the boxes when you are ready.
• Collecting virgin queens: If the cells emerge in caged compartments, the virgin queen can be given to a mating nucleus directly in her cage; cells that do not emerge or are defective are sorted out.
• Transport to distant apiaries: Portable incubators that run in a vehicle carry the cells without any loss of temperature.
• Rest after insemination: In laboratories that carry out instrumental insemination, queens are kept briefly in their cages in a warm cabinet after the procedure.

If the cells are distributed on time, an incubator is not essential; its real benefit shows with large batches and tight schedules.

What temperature and humidity should a queen incubator have?

Inside the hive the brood nest is kept at roughly 34–35 °C, and the incubator imitates this condition. Published standard methods for queen rearing recommend about 34.5 °C and high relative humidity (about 70%).

Overheating kills faster than chilling. For this reason the thermostat is set slightly on the low side, and the inside of the cabinet is always checked with a second, independent thermometer.

What should you look for when choosing an incubator?

• Thermostat precision: A digital thermostat that measures to a tenth of a degree and holds a narrow range is preferred. Simple on/off thermostats can cause wide fluctuations.
• Independent thermometer and alarm: An alarm that warns when the temperature leaves the set range saves the batch when a fault happens at night.
• Humidity control: A water reservoir or an automatic system with a hygrometer; in cabinets that only have a water dish, humidity should be monitored with a separate meter.
• Air circulation: A gentle fan reduces temperature differences inside the cabinet; the fan must not blow directly onto the cells and dry them out.
• Cell slots: An interior layout suited to a perforated rack that holds the cells upright, or to rows of cages.
• Power backup: The ability to run on an uninterruptible power supply or a vehicle battery; essential in areas where power cuts are common.
• Ease of cleaning: Interior surfaces that can be wiped, and corners that do not collect wax and fondant residue.

Egg incubators can also be used for queen cells; however, the temperature and turning mechanisms set up for poultry eggs are not suitable for queen cells. Turning must be switched off and the temperature set using an independent thermometer.

How are queen cells placed in the incubator?

1. Timing: Cells are taken on days 9–10 after grafting, when the pupa has hardened. Moving cells in the days immediately after capping is risky.
2. Transport: From the finisher to the incubator the cells are carried upright, without jarring, in a warm container.
3. Sorting: Short, curved or thin-walled cells, or cells torn open from the side, are removed at this stage.
4. Separate compartments: Each cell is put in its own slot or protective cage. The cage should contain a little fondant.
5. Labelling: The batch number and grafting date are written on the cages or the rack.
6. Monitoring: The cabinet is checked several times a day via the thermometer and hygrometer without opening it; the door is opened as briefly as possible.

What happens to a virgin queen that emerges in the incubator?

When a virgin queen emerges she can manage for a few hours on the fondant in her cage, but the incubator is not a place for long-term care. The younger virgin queens are when introduced, the more readily they are accepted; so they should be given to a mating nucleus on the day they emerge, or within one or two days at most. Acceptance of a virgin queen that is a few days old becomes noticeably harder.

• Emergence check: A cell whose tip has opened neatly like a lid indicates a healthy emergence.
• Defect check: Virgin queens with crumpled wings, damaged legs, or that are very small are not used.
• Cells that do not emerge: A cell that has not opened after several days is examined; it may indicate a dead pupa, chilling or a heating error.

Holding in the hive instead of an incubator

If there is no incubator, the bees do the same job: ripe queen cells are put individually into emergence cages and held in a strong colony, in the upper box where the queen is kept below an excluder, or in a queenless, populous colony. The bees regulate temperature and humidity themselves, and the emerging virgin queen stays in the cage in the bees' care. There is no electrical risk, but the hive has to be opened for every check.

Maintenance, cleaning and safety

• Cleaning: After each batch, cages, racks and interior surfaces are cleared of wax, fondant and dead bee debris, wiped with an odourless cleaner and dried thoroughly.
• Mould: Mould can grow in cabinets running at high humidity; change the water in the reservoir regularly.
• Calibration: At the start of the season, run the cabinet empty for a day and confirm temperature stability with two separate thermometers.
• Location: A room out of the sun, where the temperature does not swing much; the cabinet's own thermostat can only partly compensate for changes in outside temperature.
• Disease: Cages from a batch showing signs of disease are not reused without cleaning.

Common mistakes

• Relying on a single thermometer: A thermostat failure can only be detected by an independent measurement.
• Putting cells in without separating them: Among uncaged cells, the first queen to emerge kills the others.
• Opening the cabinet often: Temperature and humidity drop every time it is opened.
• Keeping virgin queens for days: Acceptance becomes harder and the queen deteriorates.
• Using an egg incubator without adjusting it: The turning mechanism and a different temperature damage queen cells.