The value of a frame of brood


When inspecting a colony, we take many things for granted if they do not appear out of the ordinary. However, it is useful to stand back and consider the value of such items to both bees and beekeeper.

During the main part of the season, some brood frames are largely filled with sealed brood and older larvae. Often, you just check quickly to ensure the bees have not tucked queen cells down by the side bar or above the bottom bars. But what is the real value of such a frame?

The queen’s normal laying pattern begins in the middle of the frame and progresses outwards in concentric circles. Assuming the sealed cells are in the centre, this is the oldest brood. If the age of the unsealed larvae gets younger towards the outside, you know your queen is present and laying well – at least she was eight days or so ago!

Boosting colony numbers

Sealed/older brood means new adult worker bees will hatch soon to boost colony numbers. Finding such frames shortly before an anticipated honey flow promises a greater foraging force to take advantage of the crop. As new bees emerge, they will take over the nursing and house duties from others who can then begin to forage. However, if this is the situation as the nectar flow is finishing, your colony could become short of food, especially if you remove the supers. In extreme cases, you may have to feed your bees with sugar syrup or candy.

Healthy brood

Most importantly, your frame of brood shows your colony’s health status. Firstly, you must learn to recognise the appearance of healthy brood. Mature larvae are pearly white, curled neatly in the bottom of the cell in a distinct ‘C’ shape. At this stage they fill the cell and the segmental divisions become apparent. Sealed cells have light-to-dark brown, slightly convex cappings which look dry.

Once you are familiar with healthy brood, any abnormality will immediately catch your attention and can be investigated further.

Drone-laying queen or laying workers?

Drone brood usually occurs in patches at the edges and bottom of the frame.

If the worker cells are interspersed with raised cappings of drone cells, suspect your queen was not properly mated and has insufficient sperm stored in her spermatheca to fertilise the eggs she lays in worker cells. She usually continues to lay in a regular pattern. As the workers try to accommodate the larger drone larvae, the cells are deformed, disrupting the uniform sealed brood pattern and the comb surface becomes uneven.

A deformed, irregular pattern of sealed cells may also indicate your colony is queenless and has laying workers. When a colony cannot or fails to replace a lost queen, workers develop functional ovaries and start laying eggs, often several in one cell. However, these are unfertilised and develop into dwarf drones. The brood pattern is disrupted.

What abnormalities might you see?

Sunken, greasy cappings, maybe with small perforations, are indicative of American foulbrood (AFB). The spore-forming bacterium, Paenibacillus larvae subsp larvae, develops in the larva’s gut and kills it after the cell is sealed. The contents decay to a dark yellowish slime. If you poke a matchstick into the cell, stir it around and withdraw it slowly, the contents will form a ‘rope’ which can be extended for 10–30 mm before breaking. The larval remains dry out to a very dark brown scale which is difficult to remove. You can see these by looking down into the cells held at an angle to a light source.

Larvae in open cells may be lying at awkward angles and appear yellowish-brown, taking on a ‘melted’ appearance. Some cappings may be sunken and perforated but the contents do not ‘rope’ as with AFB. Dry scales can be removed easily from the cells. This indicates your colony may have European foulbrood (EFB). The bacterium Melissococcus plutonius infects the gut and competes with the larva for food, usually killing it by starvation shortly before the cell is sealed.

Do uncapped cells among the sealed brood contain chalky white or mottled grey ‘mummies’? Your bees have chalk brood, caused by a fungus, Ascosphaera apis, which kills larvae before sealing. The bees can remove the mummies easily and you may find them scattered on the floor.

Uncapped cells may also indicate sac brood, a virus infection. The larva dies before its final moult, the last skin remaining intact. Sac brood can look like AFB as the larva dies on its back with its head pointing upwards, the fluid-filled membrane resembling a ‘Chinese slipper’. The contents turn yellow, then black. However, unlike AFB scale, the sac is easily removed from the cell.

Bald brood also results in uncapped cells. This can be genetic or caused by damage to the comb by wax moth larvae. The cells often have a raised lip and the pupae inside continue developing to emerge in due course.

Wax moth larvae tunnel under the cappings, leaving a silken web and a trail of small black droppings. Uncapped cells are often seen in rows among the sealed brood. In extreme cases, whole areas of cells can be covered with webbing.

What do you do?

If you discover anything abnormal, you need to take action for the sake of your bees.

If you suspect AFB or EFB you must, by law, notify the relevant authorities. Contact the National Bee Unit (0300 3030094) if you live in England or Wales, Science and Advice for Scottish Agriculture (, or the Department of Agriculture and Rural Development, Northern Ireland (028 3889 2374). An inspector will come and look at your bees and take the appropriate action.

If you suspect one of the other problems, the remedy is in your hands.

Depending on the time of year, a failing queen can be replaced or she can be removed and her colony united to a queenright one.

If laying workers have only just started, you can try to reverse the situation by introducing a comb of young brood from another colony on which the bees can raise queen cells. If laying workers are well established, shake them off their combs and remove the hive. Generally they will be accepted by a neighbouring colony, provided it is strong, and will return to normal in a queenright situation.

A strong colony is the best protection against pests and diseases. The definition of ‘strong’ obviously varies during the year. Record the number of frames of brood at each regular inspection. This should increase or decrease as the season progresses. If it does not increase in the spring, check what is wrong. With more than one colony, you can see if all are at approximately the same stage, assuming you compare like with like.

A weak one can be strengthened with sealed and emerging brood from a very strong one. Clear the comb of all adhering bees before transferring it and don’t forget to fill up the gap in the strong colony or the bees will fill it with wild comb. However, before transferring any combs, you must make sure all colonies involved are healthy. The beekeeper is one of the major causes of spread of disease through movement of combs, honey and equipment between colonies. Don’t waste healthy brood by putting it into an ailing colony.

For severe cases of sac brood, bald brood and chalk brood, consider requeening your colony from one that does not show the symptoms.

What use is my comb of brood to me?

As well as strengthening a weak colony, your frame can be used to boost a strong colony prior to an anticipated nectar flow near your apiary or migration to a particular crop. It is also an essential part of a nucleus, whether this is for raising and mating a new queen, housing an old queen or making colony increase.

It is easy to take the brood for granted but this really is the key to the colony’s status. We feel good when we see the queen but it is her brood which tells the real story. 

Written by Claire Waring. This article appeared in the February 2019 issue of Bee Craft Magazine

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