Bees

Bee brood

The three development stages in bees are collectively known as brood. The three stages are the egg, larva, and pupa stages. A bee’s entire development takes place in an individual beeswax cell of the beeswax comb.

Bee development

Bees begin their life in the tiny white egg stage. A queen normally deposits one egg in a comb cell. The eggs are about the diameter of a pin and initially stand on end in the cell, leaning over to flatten to the cell bottom as the bee embryo develops. They are very difficult to see. Beekeepers will need to develop the skill to confirm their presence. The eggs that will develop into workers and queens are fertilized before leaving the queen, while the eggs that will yield drones are not. We cannot tell the difference between fertilized and unfertilized eggs, but the bees can. If the queen makes a mistake, the egg is removed and destroyed by worker bees. The egg stage lasts three days.

 

Worker brood cells: from capped (top) to eggs (toward center), with larvae in between; photo by The BeeMD photo collection
Laying workers and multiple eggs in cells; photo by Zachary Huang, beetography.com
 

Multiple eggs in worker cells usually signals a laying worker condition in the colony. This can occur when the colony becomes queenless and for whatever reason does not successfully requeenrequeen:
to replace a queen; old queens are often removed and replaced by a ripe queen cell or by a mated queen via an introduction cage
. If drones are being raised in worker cells the queen might be a drone layer. A drone laying queen might have run out of sperm or more likely lacks viable sperm, so she places unfertilized eggs in the worker comb cells. Colonies with either laying workers or a drone laying queen are unlikely to survive, even if diagnosed correctly by the beekeeper.

The egg doesn’t hatch; it has a thin outer covering and after three days melds into a larva. The bee larva (plural: larvae) is a legless and featureless white grub. It is specialized to eat and never leaves the individual wax cell. Larvae grow at a rapid rate in a five-step development called metamorphosis, eventually increasing 1500 times their original size. Each growth step is known as an instar. The larvae are visited 10,000 or so times during their development by adult nurse bees for inspection, feeding, and eventually cappingcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
of the cells. Adult worker bees (termed nurses) bring food and place it in the cell. They do not directly feed the larva. The larval development stage for drones is 6.5 days, workers 6 days, and for queens 5.5 days.

The larvae are C-shaped. Barely visible in the first instar, they fill the bottom of the cell by their three development days. Age can be determined by their size. Colony health can be determined by how plentiful nurse bees mass provision cell supply to the first three instars. Healthy cells should have a creamy-white food pool with the larvae on top of its food. Cells with less food may show larvae seeking to crawl out of their cells, evidence of nutritional stress, which might be due to a lack of a sufficiently abundant nurse bee population. Beginning with the third instar larva, the bee progressively provision their larvae. Food is added on demand; we do not understand the signals that pass from developing larva to adult bee.

Open worker brood; some cells contain one egg, one has two eggs, and some have first instar larvae; photo by Robert Snyder
Worker larva; photo by BeeInformed
Mixed brood; open cells with larvae and capped pupae; photo by Robert Snyder
 

When fully grown and filling the cell, the larva changes to a pupa (plural: pupae). The pupal stage, frequently termed cappedcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
stage, is one of body change. The grub-like larva rapidly takes on the features of the adult; it does not get fed during this time. This last stage includes a prepupa form that spins a thin silken cocooncocoon:
very thin, protective silk envelope which an insect larva or pre-pupa forms about itself by spinning the envelope while inside the cell, to change to the pupal stage
inside the cell before conversion to the pupal stage (within a day). During the pupal and prepupal stage, the cell is sealed with a wax cappingcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
. The eye color of developing pupae beneath the brood cappingcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
changes from white to dark black as the pupa matures. The intermediate stages of pink and purple eye color can be used to approximate pupal age. The pupal development stage for drones is 14.5 days, workers 12 days, and queens 8 days.

Three stages of worker brood; illustration by Margarita Meyer
Drone pupa at purple eye stage (top); photo by Lawrence John Connor
 

The total development days are 16 days for queens, 21 days for workers, and 24 days for drones. These are averages; there can be variation of several hours to a day or more in development time. For example, if brood nest temperature drops, development takes longer.

Resource - Bee development

Bee-Health. 2019. Bee Brood (Basic Bee Biology for Beekeepers). Bee Health. Accessed 2023. https://bee-health.extension.org/bee-brood-basic-bee-biology-for-beekeepers/

Royal jelly, the larval food

All bee larvae (female and male) receive a jelly-like food. Food is placed in the cell with an egg about to transform into the larva. Larval food is termed royal jellyroyal jelly:
a protein-rich secretion of the worker's hypopharyngeal glands fed to all young bee larvae. Sometimes termed worker jelly to when it is the food fed to the worker larvae for the first three days of worker larval development; the queen receives this food throughout her larval development
; it is a protein-rich food made in head glandshead glands:
nurse-age bee glands that produce worker jelly or royal jelly. which is fed to developing larvae; these glands are usually mandibular and hypopharyngeal glands
of adult worker bees. Initially the cell with a young larva is mass provisioned. A pool of royal jellyroyal jelly:
a protein-rich secretion of the worker's hypopharyngeal glands fed to all young bee larvae. Sometimes termed worker jelly to when it is the food fed to the worker larvae for the first three days of worker larval development; the queen receives this food throughout her larval development
is kept replenished in the bottom of the cell, and the C-shaped larvae simply lies in a pool of its food. After 2.5 to 3 days, however, the diet of the worker and drone larva changes to a mixture of pollen and nectar, and food is not so generously supplied. This is called progressive-provisioning. The queen larva remains on a diet of royal jellyroyal jelly:
a protein-rich secretion of the worker's hypopharyngeal glands fed to all young bee larvae. Sometimes termed worker jelly to when it is the food fed to the worker larvae for the first three days of worker larval development; the queen receives this food throughout her larval development
, continued in generous supply, her entire larval life.

There are differences in the jelly, with the worker food sometimes termed worker jelly instead of royal jellyroyal jelly:
a protein-rich secretion of the worker's hypopharyngeal glands fed to all young bee larvae. Sometimes termed worker jelly to when it is the food fed to the worker larvae for the first three days of worker larval development; the queen receives this food throughout her larval development
, a term sometimes reserved for the food of a developing queen. Differentiation of the two females (termed a castecaste:
reproductive division of labor within female bee adults; a single reproductive female queen (via pheromone secretions) maintains more or less sterile female workers
system) is considered due to the quantity and quality of food. The larva destined to be queens receive a higher quality and a greater quantity of food. The queen jelly includes a higher amount of sugar.

Studies have sought to determine exactly what component(s) of the larval diet might be responsible for the faster development, the difference in body size, and development of large numbers of ovarioles (where eggs are produced) in queens. One study indicated one of the most common proteins, royalatin, caused the difference in body size, but this theory has not been reproduced in other studies. The magic of larval food differences remains elusive.

Drone, worker, and queen brood differences

The worker and drone brood cells are horizonal in orientation. There is a size difference; workers develop in six-sided comb cells, roughly 5 cells to a linear inch. Drone cells are larger, roughly four to an inch. During the pupal stage, worker cell cappings are slightly convex and brownish in color. The six-sided cell is clearly visible in the cappedcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
cells. Drone cell cappings are dome-shaped and often lighter brown in color but due to the elevation not as clearly six-sided in shape. Drone brood cappings extend 1/3 - 3/8 inches outward from the comb face. Cell cappingcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
wax will darken as worker bees walk over it.

Capped drone brood interspersed among capped worker brood with large section of drone brood on right side; photo by Mark Dykes
Queen cup; photo by The BeeMD photo collection
Capped queen cell; placement and summer occurrence would indicate supersedure cell; photo by Dewey M. Caron
Developing queen larva; photo by: Dan Borkoski
 

Queen brood cells are distinct from either worker or drone brood. Queen cells are oriented vertically, opening downward rather than horizontally. Queen cells, initiated by the queen, develop from queen cups. A queen cups is a cup-shaped beeswax cell, rather than six-sided as are worker and drone cells. When occupied, it is termed a queen cell. The queen cells extend from half to almost an inch in length. CappedCapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
queen cells grow to roughly the shape of a peanut.

When the queen lays eggs in queen cups, in preparations for swarming, she puts a fertilized egg in several cups over a two-to-five-day time period. Cups receiving her eggs are usually at the margin of comb. In supersedure, the queen may lay eggs in only a couple to a few queen cups. In supersedure, she more often places eggs in cups positioned on the face of the comb itself. Recently we have come to understand that eggs queens lay in swarm or supersedure cells are larger in size compared to eggs in worker comb cells. Larger eggs and differences in food quality result in healthier queens.

Emergency queen cells, developed by workers in the absence of a queen, are modified from horizontal worker cells into the vertical orientation. In a lab, queens will develop normally in a horizontal position, and workers can develop when reoriented vertically. In a colony setting, the bees will abort cells that are incorrectly positioned. Remains of queen cells are often evident for a couple weeks following successful rearing of a new queen. Queen cups are present all the time but are especially prominent and freshly constructed during spring colony development. During the rest of year, they may be removed.

Handling brood cells

Bee brood in egg and larval stage are generally secure within their cells. Beekeepers may tip the comb frames without danger of the brood falling out. Frames may be shaken or the covering mantle of adult bees removed via brushing without damaging the developing brood. The brood, however, are in danger of dehydration or chilling if kept without adult bee coverage for a period of time, depending upon temperature and duration.

Grafted queen cells; photo by Jose Uribe, The California Beekeeper

Queen cells are commonly handled by the beekeeper when rearing new queens. Queen failure is consistently identified as one of the top contributors to colony loss or poor colony performance. Beekeepers manage to replace failing queens and divide healthy colonies using queen cells initiated by the queen or by creating a queenless colony to rear emergency queen cells.

Queen brood cells are sensitive to temperature and movement. Success and survival when using queen cells to requeenrequeen:
to replace a queen; old queens are often removed and replaced by a ripe queen cell or by a mated queen via an introduction cage
depends on proper timing, preparation, and handling. Shipping (transport) of queen cells, even for short distances or time, requires special handling. They need to be continuously kept warm. Temperature fluctuation or movement injury (especially on 8-9th development days) can result in death of a developing queen or damage to developing wings, legs, or body parts.

Capped queen cells can be carefully cut from comb (beekeepers can harvest "extra" swarm or emergency cells), without damaging the cell itself for transfer to another colony. Individual queen cells should be carefully pressed into the area of brood of receiving colony so they don't fall. It is far safer to transfer the entire frame/comb containing the developing queen cell rather than trying to remove and transfer individual swarm or supersedure cells.

Commercial queen producers raise thousands of new queens annually by transferring (grafting) one-day old worker larvae into plastic or beeswax queen cups to place into queenless colonies established to rear queens. Successful cells at the cappingcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
stage are removed to an incubator or left in queenless colonies until just before emergence of a new virgin queen. CappedCapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
cells might be protected by cell protector cages.

Capped queen cells can be used to replace a mated queen or placed in mating nucleusnucleus:
also called a "nuc;" a smaller colony of bees usually with three to five frames. Nucs are splits (divides) made from larger colonies. Nucs are purchased as a method of starting a new colony or as a resource to use to bolster weaker colonies. See more information about nucs <a href="index.cfm?pageID=3093#standard">here</a> and <a href="index.cfm?pageID=3417#nuc">here</a>. 
colonies for emergence and mating. Once mated they can be placed in a queen cage to be introduced to a new colony. It is critical to avoid an emergent queen during the queen rearing process - if this happens, unemerged, developing queen cells can be destroyed by the queen chewing a hole in the side of the cell (see "Hole in queen cell" section below).

Resources - Handling queen/brood cells

Topizthofer E, Mahoney M and Sagili R. 2021. Guide to shipping honey bee queen cells. Oregon State University. Accessed 2023. https://projectapism.org/uploads/1/0/5/7/105706229/queen_shipping_guide_final_pdf_for_download.pdf

Brood pattern

Healthy bees have a solid brood pattern with few open cells. Most of the brood cells (95%+) should be occupied with developing bees of approximately same age. The percentage may be lower in early spring or later in the fall. The amount of brood (indicated by how many frames have brood and how much brood is on each frame) should be adequate for time of season. The normal brood “pattern” (the area occupied by brood in the comb) should be spherical or sometimes oval in shape and extend across more than a single frame. The brood area should be adequately covered by adult bees to maintain proper brood rearing temperature (in the 90s °F or about 32 to 34 °C). We use brood pattern to assess size of adequateness of queen and total brood area to estimate size of bee colony.

Normal pattern of frame with capped worker brood semicircle below capped honey. photo by Dewey M. Caron
Spotty capped brood pattern; photo by Robert Snyder
 

Capped honey cells might be confused for capped brood. Generally, the cappingcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
on bee pupae shows the six-sided cell condition, whereas cappedcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
cells of honey may appear more like a sheet of wax cappingcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
. Open brood cells may appear empty unless closely examined with light (and magnification) to illuminate the bottom of the cell. Eggs and very early first instar larva are very difficult to see. The open cells may be backfilled with ripening nectar rather than eggs or larvae, especially when there is a strong nectar flow.

The opposite of a healthy brood pattern is a pattern that is spotty or irregular. This might be difficult to diagnose with hygienic bees in the fall, and patterns might be spotty in early spring or later in fall, especially if the temperature of the brood rearing area drops during colder evenings or a change in weather drops the temperature quickly. Chilled brood will likely initially show at the margins of the brood area. In a deadout necropsy, scattered capped brood cells, often partially opened, may occur over one to several frames if parasitic mite syndrome is diagnosed. In the case of starvation, the capped brood cells will be more of a solid pattern and the dead cluster might be situated on top of this dead capped brood.

Resources - Brood pattern

Lee K, et al. 2019. Is the Brood Pattern within a Honey Bee Colony a Reliable Indicator of Queen Quality? Insects 10(1): 12. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6359415/

Zawislak J. n.d. Reading the Brood Pattern. Honey Bee Health. Accessed 2023. https://beehealth.uada.edu/assets/pages/broodpattern.html

Hole in developing queen cell

When a virgin queen emerges, she locates queen cells of potential rival virgin queens and eliminates them one at a time by chewing a hole in the (potential rival) queen cell. This signals workers to remove (cannibalize) the developing queen. Queen cells with a hole in the side are not normal - successful queen emergence will be via the tip of the cell. Cells with holes or cell remains from which queens have successfully emerged may persist for a week or more after queen replacementqueen replacement:
removal of an old queen and installation of a new queen in a bee colony
behaviors are finished.

Hole chewed in side of queen cell, thus halting queen development; photo by Larry J. Connor
Developing queen cells, originally grafted into plastic queen cups, destroyed by virgin queen; photo by Rob Synder
 

This behavior of queen cell destruction occurs most frequently during swarming and when numerous emergency queen cells occur in a colony as part of queen replacementqueen replacement:
removal of an old queen and installation of a new queen in a bee colony
(in both instances there will be several queen cells developing).

It is possible to protect developing queen cells with a cell protector cage to prevent queen injury to side of cell in queen rearing situations.

Break in brood cycle

A healthy brood nest will show all three development stages—eggs, larvae, and pupae—in approximate ratio of 1 egg to 2 larvae to 4 cappedcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
pupae. An imbalance of expected ratio may be noted, but it takes experience and careful examination to diagnose an imbalance.

A brood cycle break might be observed with apparent lack of eggs and/or larvae in cells. Another break observance might be realized when comparing one colony to another. An imbalance may occur following queen replacementqueen replacement:
removal of an old queen and installation of a new queen in a bee colony
behavior in which case the remains of queen cells might be observed. Certain miticide treatments and external pesticide treatments to the foraging area of a colony might cause the queen to halt egg laying or the bees to cannibalize their larvae. Cleaning cells of a larval disease outbreak may lead to imbalance. Hygienic behavior of removing cappedcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
pupae, as workers search for cappedcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
cells with reproducing varroa mites, will lead to an imbalance in brood (and eventually adults) in a colony.

Too few adults or lack of open brood may signal brood break; photo by Robert Snyder
 

A brood break may be environmentally-related such as during or following heat or cold stress. Weather may adversely affect forage and lead to a pollen or nectar dearth. Weather changes may sharply reduce foraging, leading to bees reducing their brood rearing. The need to air condition colonies due to hot temperatures might reduce pollen foraging, and if the colony lacks sufficient stored bee bread, the bees will need to reduce their brood rearing.

Feeding colonies sugar syrup and/or protein may speed colony recovery; sometimes requeeningrequeen:
to replace a queen; old queens are often removed and replaced by a ripe queen cell or by a mated queen via an introduction cage
may help speed recovery. On the other hand, creating a brood break by splitting/dividing a colony is a non-chemical means of varroa control.

Resources - Break in brood cycle

Moore P. 2015. Honey Bee Queens: Evaluating the Most Important Colony Member. Bee Health. Accessed 2023. https://bee-health.extension.org/honey-bee-queens-evaluating-the-most-important-colony-member/

The Apiarist. 2020. Queenrightqueenright:
a colony with a healthy, worker egg-laying queen; the opposite of a queenless colony
… or not? The Apiarist. Accessed 2023. https://theapiarist.org/queenright-or-not/

“12 Using RequeeningRequeen:
to replace a queen; old queens are often removed and replaced by a ripe queen cell or by a mated queen via an introduction cage
and Brood Interruption to Control Varroa Mites 11116”. YouTube, uploaded by Honey Bee Health Coalition, 2 December 2016, https://www.youtube.com/watch?v=GnPBIStvC60

Cannibalism of brood

Bees on occasion will cannibalize brood. It is a normal and fairly common means by which the adult worker population might regulate their resources during spring. Worker bees will remove diseased brood. Currently, removal of capped brood from cells with reproducing mites is a desirable bee trait; this is termed hygienic behavior and the bees hygienic bees. Removing diseased, damaged brood is basic hive sanitation. Bees are currently being bred to be hygienic, although the practice goes back 100 years when bee stocks more resistant to American foulbrood were first developed.

Resources - Cannibalism

Posada-Florez, F, et al. 2021. Pupal cannibalism by worker honey bees contributes to the spread of deformed wing virus. Scientific Reports 11: 8989. https://www.nature.com/articles/s41598-021-88649-y

Resources

Seifert P, Buling N and Grunewald B. 2021. Honey bee behaviours within the hive: insights from long-term video analysis. PLoS ONE. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0247323

Oliver R. 2015. Understanding colony buildup and decline: Part 6 - Hiccups in colony linear buildup. Scientific Beekeeping. Accessed 2023. https://scientificbeekeeping.com/tag/rainy-weather/

“Honey bee hygiene: Cannibalism”. YouTube, uploaded by ApisProtect, 15 April 2021. https://www.youtube.com/watch?v=m_PPDFMgQV8

Shaw W. 2010. There are queen cells in my hive, what should I do? Welsh Beekeepers’ Association. 25 pp. https://wbka.com/wp-content/uploads/2021/12/wbka-booklet-english-PDF.pdf

Caron DM and Greve C. 1979. Destruction of queen cells placed in queenrightqueenright:
a colony with a healthy, worker egg-laying queen; the opposite of a queenless colony
Apis mellifera colonies. Annual Entomological Society of America. 72: 405. link to this paper

Milbrath Meghan. 2020. Working with queen cells. American Bee Journal 160(9): 973-977. https://bluetoad.com/publication/?m=5417&i=670156&view=articleBrowser&article_id=3741140&ver=html5 and https://bluetoad.com/publication/?i=670156&p=37&view=issueViewer

Anton K, Boyle N and Grozinger C. 2023. Beekeeping: Cell Builder Basics. PennState Extension. Accessed 2023. https://extension.psu.edu/beekeeping-cell-builder-basics

“Queen Bees Battle to the Death”. Facebook, uploaded by Animal Planet, 28 August 2018. https://www.facebook.com/watch/?v=308758423003650

Kamakura M. 2011. Royalactin induces queen differentiation in honeybees. Nature 473(7348): 478-83. https://www.nature.com/articles/nature10093

BlythewoodBeeCompany Admin. n.d. How does Royal Jelly Make a Queen Bee? Blythewood Bee Company. Accessed 2024. https://blythewoodbeecompany.com/blogs/news/how-does-royal-jelly-make-a-queen-bee

Field J. 2005. The evolution of progressive provisioning. Behavioral Ecology 16(4): 770–778. https://doi.org/10.1093/beheco/ari054

“The life Cycle of a Honey Bee – The First 21 Days of Honey Bee’s Life” YouTube, uploaded by Discover Agriculture, 14 July 2019, https://www.youtube.com/watch?v=yrZcBk6xKtU

Buzz About Bees. 2023. Honey Bee Life Cycle. Buzz About Bees. Accessed 2024. https://www.buzzaboutbees.net/honey-bee-life-cycle.html