Splits and Emergency Queen Cells
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Queens Development
All fertilized eggs have the potential to become a queen or a worker, while unfertilized eggs become drones. All eggs hatch into larvae about three days after being laid and all larvae are fed royal jelly exclusively for the first three days after hatching. To be clear the term hatch or hatching is used to refer to bee eggs hatching into larvae and the term emerge is used when a bee emerges from its cell as an adult.
Royal jelly is a sweet, protein-rich secretion exuded from the hypopharyngeal glands of worker bees. These glands are located along the sides of a worker’s head and are largest in nurse bees between 6 and 12 days old. As workers grow older, the hypopharyngeal glands shrink and become increasingly less productive. Nurse bees consume large quantities of pollen and nectar to produce the copious amounts of royal jelly required for queen production so colonies with greater access to resources are able to rear larger numbers of well-provisioned queens. Every larva receives about 10,000 nurse bee feeding visits during development – this means that each larva is fed on average every 43 seconds.
It is possible for all female larvae under three days old to become a queen, though larger, more vigorous queens are produced with the youngest larvae, less than one day old. Larvae selected to become queens receive more royal jelly throughout development, thus younger larvae have a greater opportunity to receive optimal nutrition and meet their full potential. In contrast, worker-destined larvae transition to a ‘worker jelly’ diet on the third day. Worker jelly is a mixture of royal jelly, pollen, and nectar. Larvae exclusively fed royal jelly develop into reproductive queens while larvae fed worker jelly become sterile workers.
Upon emergence, a virgin queen spends five to eight days in the colony prior to taking her mating flight(s). Nurse bees continue to feed her during this time, allowing her reproductive organs to mature and her flight muscles to grow strong in preparation for mating flights. Also, the appearance of a virgin queen differs from a mated, laying queen. Before maturation, her ovaries have not fully developed, thus her abdomen is not yet distended, allowing her to move quickly across the comb and take mating flights.
Figure A shows the virgin, unmarked queen. Figure B is the same queen after mating. This queen is laying and marked.
Ovary Size and P-coumaric Acid
In the eusocial honey bee Apis mellifera, with reproductive queens and sterile workers, a female larva’s developmental fate depends on its diet; nurse bees feed queen-destined larvae exclusively royal jelly, but worker-destined larvae receive royal jelly for 3 days and subsequently jelly to which honey and pollen are added. RNA-Seq analysis demonstrated that p-coumaric acid, which is omnipresent in honey and beebread, differentially regulates genes involved in caste determination. Rearing larvae in vitro on a royal jelly diet to which p-coumaric acid has been added produces adults with reduced ovary development and size. Thus, consuming royal jelly exclusively not only enriches the diet of queen-destined larvae but also may actually protect them from inhibitory effects of phytochemicals ever-present in the honey and beebread fed to worker-destined larvae.
Royal Jelly vs Worker Jelly
There are few reports on the differences between royal jelly (RJ) and worker jelly (WJ). Some studies have shown that the moisture content of RJ is lower than that of WJ. Sugar is another important factor that may influence caste determination. It was found that the food of 1- to 3-day-old queen larvae contained 12.4 % sugars, which was approximately four times that found in WJ. Studies have also found that adding sugars to WJ induced larvae to become queens. Recent reports have noted that caste determination in honey bees is influenced by a 57-kDa protein in royal jelly through an epidermal growth factor receptor (EGFR)-mediated signaling pathway. While these studies strongly suggest a close relationship between food nutrients and caste determination, there is still little knowledge regarding the differences in chemical composition between RJ and WJ, such as the content of proteins, lipids, 10-hydroxy-2-decenoic acid (HDA) and mineral elements.
- Protein Power: RJ has significantly more protein, fueling the queen’s rapid growth and reproductive prowess, while WJ supports worker bees’ non-reproductive roles.
- Specialized Ingredients: RJ is rich in royalactin, a unique protein that triggers queen development, absent in WJ.
- Energy Composition: RJ boasts higher lipid levels for sustained energy, whereas WJ leans on sugars to fuel workers’ labor-intensive tasks.
- Developmental Impact: The nutritional differences between RJ and WJ drive physical, reproductive, and lifespan disparities between queens and workers.
Queen Cell Types
Swarm cells are ‘planned’ by the bees and are built down from queen cups usually found at the bottom of the frames or in little nooks and crannies between the side edges of the comb and the frame. Swarming is the bees’ natural method of reproduction and involves the queen leaving her colony which means she must be replaced hence the need for swarm cells.
Supersedure cells are also planned. They too will start out as queen cups (which look a bit like the cap of an acorn) and can often be found on the face of the comb. The presence of queen cups in a colony does not necessarily mean the bees are planning to swarm or supersede; colonies build several queen cups as a matter of course and the cups don’t become cells until they contain an egg and royal jelly. There are many reasons why an old or inferior queen may be superseded. She may have been poorly mated, or her egg-laying is defective, possibly from poor nutrition. She may have been injured by wing clipping or when transferred from a queen cage or by fighting between virgins. Age or physiological problems may cause her to produce insufficient queen pheromone.
Emergency cells are not planned. As their name suggests, they are built in response to an emergency such as the loss of the queen through spring splitting or accident. these cells are developed from an egg already laid in a worker cell or very early-stage female larvae and are found anywhere on the comb where there is the right age of worker brood to start from. The drawn cell often protrudes slightly at the top where it has been adapted from a horizontal worker cell into one which is vertical.
Colony Selection of “Starter Material”
Only larva up to three days old are suitable for producing new queens i.e. six days after the egg is laid. However, if the queen is laying 1000 eggs per day that means there are up to 3000 suitably aged larvae in the hive to produce a new queen, should one be needed. There’s even more choice as the bees can start the queen rearing process – the production of a queen cell – from a cell occupied by an egg … something that has been known for decades but is relatively rarely discussed.
Almost all queen cell construction is started within 24 hours of queen removal when splitting. A few more cells may be produced for up to 48 hours after dequeening, but none are normally started after that. There will still be many hundreds of (apparently) suitably aged larvae in the colony at this point. However, these are not selected as all the queen cells that would be made have already been started.
Colonies produce different numbers of queen cells, from 6 to 56 (average 27). However, most of these cells are torn down before emergence, and a few of those that were sealed never emerge. It’s common to have 53% torn down, 5% never emerging and the remaining 43% emerge. A good reason to always leave 2 queen cells of the highest visible quality as possible (large and well formed)
The brood nest is roughly spherical and usually occupies the center of the hive. About 46% of cells started are on the central frames, and these have a much greater chance of producing queens. This was because queen cells started on the central frames of the brood nest were less likely to be torn down (41%) than those on the periphery (71%).
They predominantly choose eggs. Almost 70% of queen cells that are started are initiated when the cell contains an egg, rather than a larva. What’s more, most of the eggs chosen are three days old. Furthermore, over 60% of queen cells produced from 2-day old larvae are subsequently torn down. Bees choose to make queens from the oldest eggs or the very youngest larvae. Almost 60% of the ‘starting material’ chosen by the bees to ensure colony survival – that resulted in queen production – were 3-day old eggs or 1-day old larvae.
Workers Manage Queen Quality
Studies have shown that there is no relationship between weight and ovariole number, irrespective of the age of the egg or larva when the cell was started but some unpublished data has suggested that heavier queens may be able to achieve higher levels of polyandry i.e. mate with more drones, so increasing the genetic diversity, and consequently the fitness, of the colony. From this it could be speculated that a queen with a larger thorax may have better developed flight muscles. These might enable her to stay longer in drone congregation areas for mating.
Studies also indicate that workers are somehow ‘weeding out’ lower quality (defined as smaller and probably lighter) queens. These results suggest that workers regulate the queen rearing process by differentially constructing cells. Workers built different numbers of queen cells from different ages of brood and non-randomly destroyed over half (53%) of the initiated cells before their emergence. For those queens whose cells were not torn down, the variation in reproductive quality was limited, varying only slightly among age groups for queen size. In this way the workers regulate queen quality traits by cur-tailing low-quality queens from fully developing, which is further evidence that cooperation predominates overpotential conflict of having to many emerging queens within honey bee colonies.
Why Multiple Cells
- Colonies raise multiple queens to guarantee the requeening process. This assumes that the ‘cost’ of queen rearing is low, which seems reasonable. Since only 5% of queens raised failed to emerge it is probably not to overcome this limitation.
- Multiple queens allow colony reproduction if conditions are suitable. Only colonies that raise multiple queens would be able to (simultaneously) reproduce and requeen, so there might be a selective pressure to allow this.
- A consequence of age demographics (brood or workers) in the colony. This is slightly trickier to explain and has not been tested. Queen cells result from an ‘interaction’ of available brood (eggs/larvae) with workers. A colony has variable numbers of both, and there are a variety of worker cohorts, only some of which contribute to cell building. Therefore, the production of multiple cells (and queens) may simply reflect the variation in the factors – ages of brood and workers – involved.
- Rearing multiple queens allows workers to select ‘better” queens. It allows workers to select for better queens by destroying those of lower quality.
Conclusion
When conducting splits by removing the overwintered queen and leaving the parent colony to build emergency cells, cells are started within 24-48 hours and capped within 5 days. Workers prefer “starter material” that is selected from 3-day old eggs or 1-day old larvae which could be located anywhere on the central brood area frames that contain this age of egg/larvae. This means that unlike swarm cells found normally at the bottom of the frame and supersedure cells on the face of a frame, emergency cells can be anywhere so additional effort should be allowed to assure all cells are identified when taking next steps in managing how many cells to leave. A missed cell can encourage after swarms if not addressed.
Alternatively, if you are improving your colonies by adding larvae from a separate hive make sure you add a frame containing eggs and larvae to assure you provide starter material that fits what they prefer at the time they begin building cells which could be up to 48 hours later. It makes sense to place these frames in the center of the brood nest. Also, if you are grafting perhaps grafting from eggs rather than larvae maybe something to consider since you can’t determine exactly when the workers will have access to these cells.
It’s clear that, when allowed, the worker bees will manage this process themselves with great skill and ability producing the best queens possible for the colony and the species long term genetic survival. This should generate caution in the beekeeper understanding that interruptions to this highly delicate process are taken at the beekeeper’s risk and should be done taking every effort to work within the bee’s natural behaviors.
Referenced Materials
- Worker regulation of emergency queen rearing in honey bee colonies and the resultant variation in queen quality
- Honey bee colonies regulate queen reproductive traits by controlling which queens survive to adulthood
- Emergency queen rearing in honeybee colonies with brood of known age
- Emergency Queen Cells
- Quality of Emergency Queens
- Effect of age of eggs used for rearing honey bee queens on the number of received queen cells
- A dietary phytochemical alters caste-associated gene expression in honey bees
- Diet and Cell Size Both Affect Queen-Worker Differentiation through DNA Methylation in Honey Bees (Apis mellifera, Apidae)
- Comparison of the nutrient composition of royal jelly and worker jelly of honey bees (Apis mellifera)
- The Ontogeny and Dietary Differences in Queen and Worker Castes of Honey Bee (Apis cerana cerana)
- An Introduction to Queen Honey Bee Development
- Phenotypic dimorphism between honeybee queen and worker is regulated by complicated epigenetic modifications
- Evaluation of queen cell acceptance and royal jelly production between hygienic and non-hygienic honey bee (Apis mellifera) colonies