The Laborious Honey Bee

BugSquad By Kathy Keatley Garvey September 9, 2019

Today is Labor Day 2019, a federal holiday celebrated the first Monday of September.

However, "the girls" are working, as they do every day of the year, weather permitting.

"The girls" are the worker honey bees.

Unless you keep bees or have access to a hive, you mostly see them foraging. But inside the hive, they are also nurse maids, nannies, royal attendants, builders, architects, dancers, honey tenders, pollen packers, propolis or "glue" specialists, air conditioning and heating technicians, guards, and undertakers.

They ensure the survival of the hive, but their life span is short.

"Worker bees live for approximately five to six weeks in the spring and summer," writes author and retired bee scientist and bee wrangler Norman Gary, emeritus professor of entomology at the University of California, Davis, in his book, Honey Bee Hobbyist: The Care and Keeping of Bees."Those reared in the fall live for several months--long enough for the colony to survive the winter--and are replaced by young bees in late winter or early spring."

In peak season, a honey bee queen can lay 1500 to 2000 eggs a day, and most of them will be worker bees, the most needed of the three castes (queen, drone and worker) in the hive.  Although the smallest, but they do most of the work.  The queen is the egg layer. The drone's role is strictly reproduction.

Worker bees forage within four to five miles of their hive. If you provide no nectar or pollen sources in your yard, they'll go elsewhere.

Theirs is a dangerous occupation. No thanks to predators (such as birds, praying mantids and spiders) and pesticides, many do not return home at night.

Like to photograph them? Try the "magic hour," which occurs about an hour before the sun sets. We love photographing them on Mexican sunflowers (Tithonia). The light is soft, warm and welcoming.

(Editor's Note: Interested in becoming a beekeeper or learning more about beekeeping? Be sure to check out the UC Davis-based California Master Beekeeper Program, directed by Extension apiculturist Elina Lastro Niño of the UC Davis Department of Entomology and Nematology. The next course is on managing varroa mites, a major pest.)

Worker honey bee forages on a Mexican sunflower (Tithonia) in the magic hour, the hour before sunset. (Photo by Kathy Keatley Garvey)

Worker honey bee forages on a Mexican sunflower (Tithonia) in the magic hour, the hour before sunset. (Photo by Kathy Keatley Garvey)

Illuminated by the late afternoon sun, the worker bee prepares to fly to another Tithonia blossom. (Photo by Kathy Keatley Garvey)

Illuminated by the late afternoon sun, the worker bee prepares to fly to another Tithonia blossom. (Photo by Kathy Keatley Garvey)

A worker bee takes flight, lifting over a Mexican sunflower. (Photo by Kathy Keatley Garvey)

A worker bee takes flight, lifting over a Mexican sunflower. (Photo by Kathy Keatley Garvey)

Honey Bee Caste Systems: Part 2 – How Genetics and the Environment Shape Honey Bee Workers and Queens

Bee Informed.jpg

By Garett Slater, Former Midwest Tech Transfer Team June 5, 2019



In part 1 of my blog series, I wrote about how genetics can shape reproductive males (drones) and both reproductive (queens) and non-reproductive (workers) females within a colony. However, genetics only explains part of the story. I will describe why that is in the second installment of my 3-part series:

  • Part 1: The Genetic Book of Life-The basics to honey bee genetics (for Part 1 click here)

  • Part 2: How Genetics and the Environment Shape Honey Bee Workers and Queens

  • Part 3: The Differences Between Queens and Workers

Figure 1: Queen and Worker honey bees. As you can see, there are clear anatomical differences between these castes despite genetic similarities.

Figure 1: Queen and Worker honey bees. As you can see, there are clear anatomical differences between these castes despite genetic similarities.

Queen determination has always fascinated researchers and beekeepers. This is unsurprising considering queens and workers are genetically similar yet have distinct anatomical and physiological features (Figure 1). In fact, queens are highly fertile and lay more than 2000 eggs per day whereas workers have anatomical structures specialized for foraging, nursing and other colony tasks. So how does a colony produce either a fertile queen or a sterile, highly specialized worker, even if they have the same genetics?

Most beekeepers and queen producer know nutrition determines whether a fertilized larva develops into a queen or worker. Just place a 1-3-day old larvae into a queenless colony and watch as they develop a queen from a previously worker-destined larvae (Figure 2). However, how this nutrition determines queens has historically perplexed researchers. Since the 1890’s, diet quality has been thought to determine queen-worker castes in honey bees through a “biological active substance” found only in royal jelly. This quality hypothesis arose from early observations of queen and worker larvae receiving different proportions of water-clear and milky-white secretions from nurse bee glands. The milk-white secretion fed to queen-destined larvae was termed royal jelly whereas the water-clear secretion was termed worker jelly (Figure 3). Since then, royal jelly was thought to contain the major dietary components necessary for queen development.

Figure 2: Queen producers make queens by transferring worker-destined larvae into queen cells of breeder colonies.

Figure 2: Queen producers make queens by transferring worker-destined larvae into queen cells of breeder colonies.

Figure 3: Royal jelly (left) is fed to queen-destined larvae and worker jelly (right) is fed to worker-destined larvae.

Figure 3: Royal jelly (left) is fed to queen-destined larvae and worker jelly (right) is fed to worker-destined larvae.

The first person to empirically test differences between royal and worker jelly was Dr. Adolf van Planta in 1888 (Table 1). He concluded the food composition fed to workers changed drastically after the age of 4 days, which is when worker larvae cannot develop into a queen naturally in a colony. While the food fed to workers and queens seem striking, royal jelly content was only quantified for 1 day. However, once this study was published, researchers began to search for the substance in royal jelly that determines caste. In fact, the only other study after Dr. von Planta’s publication to compare differences between royal and worker jelly was Wang et al. 2016.

Royal jelly was then deemed special and necessary for queen development. In fact, royal jelly has been thought to contain a “pure determining substance” not found in worker jelly ever since. This has pushed scientists to find this active substance so we can truly understand how queens develop.  Researchers have tested nearly every major component in royal jelly on caste determination. In fact, most studies found positive results. They found lipids, proteins, carbohydrates, water, pantothenic acid (vitamins) and even p-coumaric acid (chemical in pollen) all contribute to queen development in honey bees under some experimental conditions. Despite positive results, how does every single macronutrient and micronutrient in royal jelly determine caste? This question perplexed me.

Table 1: Comparison between Royal and Worker jelly.

Table 1: Comparison between Royal and Worker jelly.

As I began researching royal jelly and queen development, I realized none of these studies controlled for diet quantity. This is surprising because queens are obviously fed more food than workers during development. In fact, queen-destined larvae are fed an excess of 300mg of diet and are fed 1400 times more frequently by nurse bees than worker-destined larvae. As I did a literature search, I couldn’t believe the impact of quantity on honey bee caste determination has not been formally tested. 

Figure 4: 48 well plate I use for rearing honey bee larvae on an artificial diet


Figure 4: 48 well plate I use for rearing honey bee larvae on an artificial diet

I decided to pursue this question during my masters. I used in vitrorearing techniques to test whether diet quantity causes queen development (Figure 4). In vitro rearing is a useful tool because I can become a “nurse” bee and control the food larvae receive. In fact, I can change the type of food and the amount of food larvae receive and see how that impacts development. So, I tested the relative contributions of diet quantity and quality by rearing honey bee larvae on diets that altered both quality and quantity.

Figure 5: The range of sizes I produced by changing diet quantity. I produced small workers, workers, intercastes, and queens.

Figure 5: The range of sizes I produced by changing diet quantity. I produced small workers, workers, intercastes, and queens.

A wide range of individuals were raised from my artificial diets. Not only were queens and workers reared, but also intercaste bees (part worker-part queen), or what I call them, princess bees (Figure 5). I have never seen intercaste bees in a natural hive setting nor have I seen miniature workers half the size of normal workers. Thus, it seems bees have the ability to develop into a wide range of body sizes. These results indicate 2 conclusions: 1) nutrition during development is extremely important for both workers and queens, and 2) colonies impressively control queen versus worker development. More importantly, it seems diet quantity plays a larger role in caste determination than expected.

Caste determination is fascinating and I truly enjoyed studying it, but why should the average beekeeper care? The main reason is queens are an integral component of a colony however we have little understanding about how a queen develops and which factors make a high-quality queen. This is important to improve queen quality and manifest important queen traits through breeding, selection, and alternative management practices.

Honey bee queen determination is an intersection between genetics and the environment. I hope you enjoyed reading this post and keep an eye out for the next installment on the key differences between queens and workers.

Citations

von Planta, A. (1888). Ueber den Futtersaft der Bienen. Zeitschrift für physiologische Chemie12(4), 327-354.

Wang, Y., Ma, L., Zhang, W., Cui, X., Wang, H., & Xu, B. (2016). Comparison of the nutrient composition of royal jelly and worker jelly of honey bees (Apis mellifera). Apidologie47(1), 48-56.

https://beeinformed.org/2019/06/05/honey-bee-caste-systems-part-2-how-genetics-and-the-environment-shape-honey-bee-workers-and-queens/

Honeybees All Have Different Jobs

National Geographic By Richie Hertzberg March 22, 2019

How honeybees get their jobs—explained

With brains the size of sesame seeds, honeybees have to work together in different
capacities to maintain a healthy nest.

EVERY HONEYBEE HAS a job to do. Some are nurses who take care of the brood; some are janitors who clean the hive; others are foragers who gather nectar to make honey. Collectively, honeybees are able to achieve an incredible level of sophistication, especially considering their brains are only the size of sesame seeds. But how are these jobs divvied up, and where do bees learn the skills to execute them?

Unlike in Jerry Seinfeld’s “Bee Movie,” real honeybees don’t go to college and get a job assignment from an aptitude officer upon graduation. Instead, they rely on a mixture of genetics, hormones, and situational necessity to direct them. Honeybees are born into an occupation, and then their duties continually shift in response to changing conditions in the hive.

“The jargon we use is that it’s ‘decentralized.’ There’s no bee in the center organizing this,” says Thomas Seeley, author of the book Honeybee Democracy. “Each bee has its own little set of rules, and the labor is sorted out by the bees following their rules.”

Born this way

A bee’s job is determined by its sex. Male bees, or drones, don’t do any work. They make up roughly ten percent of the colony’s population, and they spend their whole lives eating honey and waiting for the opportunity to mate. When the time comes for the queen to make her nuptial flight, all the drones in other colonies will compete for the honor of insemination. They fly after the queen and attempt to mate with her in mid-air. If they mate successfully, they fall to the ground in a victorious death. The queen will mate with up to twenty drones and will store their spermatozoa in her spermatheca organ for the rest of her life. That’s where male duties end.

Female bees, known as worker bees, make up the vast majority of a hive’s population, and they do all the work to keep it functioning. Females are responsible for the construction, maintenance, and proliferation of the nest and the colony that calls it home.

A bee’s sex is determined by the queen, who lays eggs at a rate of 1,500 per day for two to five years. She has the unique ability to designate which eggs will develop into female workers and which will become male drones.

If the queen approaches a smaller worker bee cell to lay a female egg, she will fertilize the egg on its way out by releasing spermatozoa from her nuptial flight. She has enough spermatozoa stored in her abdomen to last the duration of her life.

If the queen approaches a larger drone cell to lay a male egg, on the other hand, she will not release any spermatozoa as the egg leaves her ovaries. This unfertilized egg will develop into a drone.

Domestic duties

It takes 21 days for the worker bee to grow out of her larval state and leave the cell. When she emerges on day 21 as an adult bee, she will immediately start cleaning the cell from which she hatched. Her first three days will be spent cleaning cells to prepare them for the queen’s next round of eggs.

After three days, her hormones kick in to initiate the next phase of work: nursing the young. Seeley explains that hormones are released to activate different parts of the bee’s genes assigned to different tasks. “It’s similar to when humans get sick,” he says. “Sick genes that are involved in inflammation and fever get turned on. Likewise with bees and their jobs.”

A worker bee will spend about a week nursing the brood, feeding larvae with royal jelly, a nutritious secretion that contains proteins, sugars, fats, and vitamins. The exact number of days she spends on this task depends on where the hive needs the most attention. Bees are very sensitive organisms whose hormones are closely tied in with the colony’s needs. “A colony of honeybees is, then, far more than an aggregation of individuals,” writes Seeley in Honeybee Democracy. “It is a composite being that functions as an integrated whole.” The colony is a well-oiled superorganism, similar to ant and termite colonies.

The most dangerous job

When the bee is finished nursing, she will enter the third phase, as a sort of utility worker, moving farther away from the nest’s center. Here she will build cells and store food in the edge of the nest for about a week.

A bee’s hormones will shift into the final phase of work at around her 41st day: foraging. This work is the most dangerous and arguably the most important. It’s only done by older bees who are closer to death. As Steve Heydon, an entomologist at the University of California, Davis, puts it, “You wouldn’t want the youngest bees doing the most dangerous job.” If too many young bees die, then the hive wouldn’t be able to sustain itself.

As the worker bee approaches her fourth week of nonstop work, she will sense her end of days and remove herself from the hive, so as not to become a burden. If she dies in the hive, her fellow bees would have to remove her corpse.

Thus is the life of a female bee during the active seasons of spring and summer, compulsively working from the day she’s born until the day she dies. It’s a thankless life of nonstop work, but honeybees, as a result, are some of the most successful collaborators we’ve found in nature.

[Editor's Note: This article originally misstated what bees use to make honey. They use nectar.]

https://www.nationalgeographic.com/animals/2019/03/honey-bee-job-queen-hive-animals/?fbclid=IwAR22oQODHIUDVcWt3qY2GoZxLmL9sDZWCMPWGl9Is6dR5H3bkcSFlMdRBfE

Watch Related - Amazing Time-Lapse: Bees Hatch Before Your Eyes

Improved Regulation Needed As Pesticides Found to Affect Genes in Bees

EurekAlert From: Queen Mary University of London March 6, 2019

Bumblebee Colony Credit: TJ Colgan

Bumblebee Colony Credit: TJ Colgan

Scientists are urging for improved regulation on pesticides after finding that they affect genes in bumblebees, according to research led by Queen Mary University of London in collaboration with Imperial College London.

For the first time, researchers applied a biomedically inspired approach to examine changes in the 12,000 genes that make up bumblebee workers and queens after pesticide exposure.

The study, published in Molecular Ecology, shows that genes which may be involved in a broad range of biological processes are affected.

They also found that queens and workers respond differently to pesticide exposure and that one pesticide they tested had much stronger effects than the other did.

Other recent studies, including previous work by the authors, have revealed that exposure even to low doses of these neurotoxic pesticides is detrimental to colony function and survival as it impairs bee behaviours including the ability to obtain pollen and nectar from flowers and the ability to locate their nests.

This new approach provides high-resolution information about what is happening at a molecular level inside the bodies of the bumblebees.

Some of these changes in gene activity may represent the mechanisms that link intoxification to impaired behaviour.

Lead author of the study Dr Yannick Wurm, from Queen Mary University of London, said: "Governments had approved what they thought were 'safe' levels but pesticides intoxicate many pollinators, reducing their dexterity and cognition and ultimately survival. This is a major risk because pollinators are declining worldwide yet are essential for maintaining the stability of the ecosystem and for pollinating crops.

"While newer pesticide evaluation aims to consider the impact on behaviour, our work demonstrates a highly sensitive approach that can dramatically improve how we evaluate the effects of pesticides."

The researchers exposed colonies of bumblebees to either clothianidin or imidacloprid at field-realistic concentrations while controlling for factors including colony social environment and worker age.

They found clothianidin had much stronger effects than imidacloprid - both of which are in the category of 'neonicotinoid' pesticides and both of which are still used worldwide although they were banned in 2018 for outdoor use by the European Union.

For worker bumblebees, the activity levels of 55 genes were changed by exposure to clothianidin with 31 genes showing higher activity levels while the rest showed lower activity levels after exposure.

This could indicate that their bodies are reorienting resources to try to detoxify, which the researchers suspect is what some of the genes are doing. For other genes, the changes could represent the intermediate effects of intoxification that lead to affected behaviour.

The trend differed in queen bumblebees as 17 genes had changed activity levels, with 16 of the 17 having higher activity levels after exposure to the clothianidin pesticide.

Dr Joe Colgan, first author of the study and also from Queen Mary University of London, said: "This shows that worker and queen bumblebees are differently wired and that the pesticides do not affect them in the same way. As workers and queens perform different but complementary activities essential for colony function, improving our understanding of how both types of colony member are affected by pesticides is vital for assessing the risks these chemicals pose."

The researchers believe that the approach they have demonstrated must now be applied more broadly. This will provide detailed information on how pesticides differ in the effects they have on beneficial species, and why species may differ in their susceptibility.

Dr Colgan said: "We examined the effects of two pesticides on one species of bumblebee. But hundreds of pesticides are authorised, and their effects are likely to substantially differ across the 200,000 pollinating insect species which also include other bees, wasps, flies, moths, and butterflies."

Dr Wurm added: "Our work demonstrates that the type of high-resolution molecular approach that has changed the way human diseases are researched and diagnosed, can also be applied to beneficial pollinators. This approach provides an unprecedented view of how bees are being affected by pesticides and works at large scale. It can fundamentally improve how we evaluate the toxicity of chemicals we put into nature."

###

Research paper: 'Caste- and pesticide-specific effects of neonicotinoid pesticide exposure on gene expression in bumblebees'. Thomas J. Colgan, Isabel K. Fletcher, Andres N. Arce, Richard J. Gill, Ana Ramos Rodrigues, Eckart Stolle, Lars Chittka and Yannick Wurm. Molecular Ecology.

https://www.eurekalert.org/pub_releases/2019-03/qmuo-irn030519.php