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The Complex Life of the Honey Bee

Cover photo © Eric Tourneret

Fred Whitford, Director, Purdue Pesticide Programs
Thomas Steeger, Senior Science Advisor, Environmental Protection Agency
Max Feken, Ecotoxicologist, Syngenta Crop Protection
Christian Krupke, Extension Field Crops Specialist, Purdue University Entomology
Greg Hunt, Extension Honey Bee Specialist, Purdue University Entomology
Reed Johnson, Assistant Professor of Entomology, The Ohio State University
Corey Gerber, Director, Purdue Crop Diagnostic Training and Research Center
John Obermeyer, Integrated Pest Management Specialist, Purdue University Entomology
Krispn Given, Apiculture Specialist, Purdue University Entomology

A Complicated Question with a Complicated Answer ……………………………..4
The Buzz Surrounding Bees ………………………………………………………………….7
A Marvel of Nature …………………………………………………………………………….10
Building and Maintaining a City of Wax ……………………………………………….24
The Biology of the Honey Bee ……………………………………………………………..28
Death is a Way of Life ………………………………………………………………………..38
The Four P’s that Affect Bees ……………………………………………………………..40
Routes of Pesticide Exposure from Field to Hive ………………………………….42
Everything is Poisonous at Some Dose ……………………………………………….45
The EPA Risk Assessment Process …………………………………………………….46
The Honey Bee as a Surrogate for Insect Pollinators ……………………………48
A Host of Questions to Answer …………………………………………………………..49
Determining Many Routes of Exposure ………………………………………………52
Formulating a Working Hypothesis ……………………………………………………53
Analyzing the Data ……………………………………………………………………………53
Comparing Exposure and Effects in a Tiered Approach ………………………..54
Tier 1 — Effects to Individual Honey Bees …………………………………………..56
Tiers 2 and 3 — Colony-level Assessments ………………………………………….59
Is the Risk Quotient Above or Below Levels of Concern? ………………………61
Registration Decisions Go Through Extensive Reviews ………………………..62
The Label Puts the Risk Assessment to the Test …………………………………..63
Moving Beyond the Label ………………………………………………………………….64
Conclusion ………………………………………………………………………………………65
References ……………………………………………………………………………………….68
Appendix: Descriptions of EPA Testing Protocols ………………………………..69
Acknowledgements …………………………………………………………………………..75
Disclaimer ……………………………………………………………………………………….75

A Complicated Question with a Complicated Answer

Are honey bees in decline?

It seems like a simple question to ask. Yet, you can watch a television program or read an article that reports honey bees are in a perilous position. They report that if current trends continue, it will alter the way humans eat, or at least drive up the costs of our favorite fruits, nuts, and vegetables. Conversely, another story will argue that the decline in honey bees is contrived, and the facts do not support the conclusion that the bee industry is in dire straits.
At times contentious and controversial, some reports are anecdotal and use speculation and unsubstantiated facts laced with emotional opinions. Other discussions

are based on known facts and scientific evidence, but fall short of providing important perspective on the difficulties of maintaining honey bees — either professionally (as in commercial or sideline operations) or privately (as in backyard beekeeping).
How can these reports have such divergent perspectives? As in most debates, the answer to whether bees and other pollinators are in trouble probably lies in a careful analysis of science-based information surrounding the debate.
Discussions and debates often begin with the rather politically- and emotionally-charged words and phrases used in the first minutes of any discussion concerning

A honey bee yard seemingly tucked away from harm.

whether bees are healthy or unhealthy. You’ll often hear phrases like “bee decline” and “colony collapse disorder.” In many cases, these explicit terms become the headline, because they portray powerful mental images to the audience.
You might ask yourself, “How would I define these terms?” And, if a definition could be agreed upon, “How would I measure them?” Without some context to their meaning, bee decline, colony collapse disorder, and other terms can be rendered meaningless and confuse the issue.
Scientists, government officials, conservation groups, and industry professionals are asking plenty of questions about why beekeepers (both commercial and hobbyists) are seeing increased colony losses. One baseline often reported is that in a typical year, 28 percent of honey bee hives die during the winter season. Annual losses may be higher; this number is a source of considerable debate.
Whatever the annual baseline loss may be, the percentage of yearly losses began to routinely exceed that long-term average about a decade ago. When that happened, experienced beekeepers took notice, and many have voiced their concerns about the viability of beekeeping.

Any threat to beekeeping represents a threat to agriculture, specifically the production of fresh fruits, nuts and vegetables. This has raised the profile of the “honey bee decline” story and captured the public’s attention. We will discuss the potential causes for these trends in this publication, but regardless of the causes (at least in the short-term) these losses represent an unwelcome challenge for beekeepers. Left unchecked, these causes could potentially lead to more serious and widespread negative consequences.
Everyone from beekeepers to conservationists who want to protect diverse habitats want “The Answer” for the cause of bee declines to be proven using the best available science. While individuals search for a single cause, scientists continue to assert that, as with many biological questions, there are multiple factors    associated with declines in pollinator health. The more we learn, the more the complexities become apparent.
Even so, this does not mean there are no solutions. We already know a lot about the threats to pollinators and pollinator research is more active than ever. For example, we know that the ectoparasite mite Varroa destructor arrived in the United States in the 1980s and is the single most devastating enemy of both managed and feral bees in the United States.

Key Stressors to Honey Bee Populations

Other key stressors to honey bee populations
• Parasites like tracheal mites (Acarapis woodi),
small hive beetle, and wax moths
• Diseases (such as the fungus Nosema ceranae),
bacteria (such as American foul brood), and
viruses (such as deformed wing virus)
• Lack of suitable forage (poor nutrition) from
loss of habitat due to farming, increased human
populations, and new construction
• Pesticide exposure to honey bee foragers and
their developing young (brood)
• Beekeeper management practices, which
include the stress of transporting honey bees
across the country for pollination services

While there will always be disagreements about the causes and effects of declines in hives, beekeepers, agriculturists, scientists, conservationists, and policymakers all agree that honey bees play a pivotal role in crop production, availability, prices, food security, and the economy.
A critical first step in protecting that role in the future is to outline the current state of knowledge surrounding the debate.
There are multiple factors associated with declines in honey bee health and outright colony losses. But the most controversial is pesticides, because this risk factor involves a wide range of stakeholders who agree that both pesticides and pollinators are important to agriculture.
This publication explores the roles pesticides may play in bee health, examines the latest knowledge in this fast-developing field of research, and discusses the regulatory effort to determine the risk of pesticides to honey bees and other pollinators. To interpret the role stressors like pesticides may play in influencing bee biology and health, it is important to understand bee
biology. So, we will begin by examining that biology.

two bees on comb one with a damaged wing
The honey bee on the left has deformed wing virus.
basket of tomatoes, blueberries, and brocoflower
Many fruits and vegetables depend on honey bees for pollination.

The Buzz Surrounding Bees

Though small, the honey bee (Apis mellifera) has become the center of an intense national and international debate. Starting in the early 1980s, commercial beekeepers noticed that it was increasingly difficult to keep honey bees alive through the winter. A worried commercial beekeeping industry asked university and USDA bee specialists and researchers to address why this was occurring.
Below, we summarize the recent history behind some of the key factors — tracheal mites, Varroa mites, and colony collapse disorder — known to affect honey bee populations in North America.

Tracheal Mites
One of the initial key contributors to declining bee
populations was the tracheal mite (Acarapsis woodi), which was introduced from Mexico into a Texas apiary.
From that first detection in Texas, the tracheal mite quickly spread throughout the United States.
The microscopic tracheal mite enters a honey bee’s respiratory system through its spiracles, which are breathing holes that lead directly to the bee’s tracheae. Tracheae serve as breathing tubes, carrying oxygen
to a honey bee’s cells. When tracheal mites infest a bee, they effectively clog these tubes, reduce oxygen flow, and weaken the bee.

Losses from tracheal mites forced some apiaries out
of business. Researchers found that when 30 percent of
the honey bees in a hive are infested with tracheal mites, the hive was more susceptible to cold winter temperatures. This was largely due to bees not maintaining a warm enough temperature within the hive cluster. Some apiaries reported that half of their hives died over the winter following the introduction of tracheal mites.

If there was a silver lining to the story, it was that honey
bees and beekeepers developed various strategies to
reduce tracheal mite infestations. Although tracheal mites continue to harm some colonies, the problem has mostly subsided into the background of honey bee health issues. For the beekeepers who remained after the initial tracheal mite invasion, they observed that the honey bee industry slowly began to recover.

two bees on comb one with a damaged wing
This photograph shows a tracheal mite viewed through a microscope. © Scott Camazine

Varroa Mites

Varroa Mites

However, that good news was soon supplanted when a new and far more serious threat was introduced. The aggressive Varroa mite was inadvertently introduced to U.S. honey bees around 1987. Domestic honey bees that had no previous association with this mite were extremely susceptible. As a result, apiaries recovering from tracheal mite infestation were decimated by the Varroa mite.
Varroa mites are an external parasite that feed on the hemolymph (insect blood). It feeds off adult honey bees and their developing young (larvae and pupae). Varroa mites also transmit deadly viruses — like mosquitoes can vector viruses to humans and other mammals. Mite infestations can kill pupae outright, and many of the adult bees that survive to emerge from pupal cells show symptoms of deformed wing virus, which can be vectored by the mites.
Deformed wing virus can render the bee wings crinkled and undeveloped. Bees infected with this virus cannot fly, so they cannot function properly as part of the colony. The virus weakens the bee and eventually kills it.
Varroa infestation in the hive typically peaks in the fall. Between the damage caused by the direct feeding of mites and damage caused by deformed wing virus (and other viruses), the hive loses a significant amount of its adult labor force. These losses make it more difficult for the bees to overwinter. 

Varroa infestation in the hive typically peaks in the fall. Between the damage caused by the direct feeding of mites and damage caused by deformed wing virus (and other viruses), the hive loses a significant amount of its adult labor force. These losses make it more difficult for the bees to overwinter.
This is particularly unfortunate for the colony because a queen bee stops laying eggs in the fall, and the hive relies on heathy bees that can live through the winter to raise brood in the spring. Although it has been decades since the Varroa have been introduced, honey bees have not been able to overcome its devastating effects as they were able to with tracheal mites.
Throughout the 1990s, apiaries continued to make honey and provide pollination services despite the challenges presented by mite infestations. Beekeepers were forced to replace lost hives each year by splitting and placing healthy colonies into vacated hives, which stressed colonies even more. The result was a rapidly rising cost in agriculture.

This Varroa mite locates itself strategically to avoid being groomed off by its honey bee host. Although mites are frequently found on adult bees, the mites most seriously affect larvae. © Alex Wild
After feeding in the cell on the developing larva and pupa, this Varroa mite emerges with the adult honey bee. © Scott Camazine

Colony Collapse Disorder
In 2006 and 2007, a phenomenon known as Colony Collapse Disorder (CCD) made headline news across the country. CCD was initially defined based on symptoms: adult bees declined and the colony collapsed over the course of a few weeks, usually leaving the queen and a small number of workers in a colony with nectar, pollen, and brood still in the cells. CCD was never clearly
defined, but the spectacular disappearance of bees gripped the public’s imagination in a way that continues today, even though the CCD syndrome may not have been as widespread or as long-lasting as media reports suggested.
Growers of fruits, nuts, and vegetables who depended on commercial beekeepers for pollination services began
to worry if there would be enough honey bees for pollination. What had historically been taken for granted, took on a different meaning when the number of hives available for pollination services were significantly
reduced (and therefore more expensive to rent).
In particular, almond growers provide the most
compelling example of how much one agricultural crop relies on honey bee pollination services. California’s Central Valley grows approximately 80 percent of the world’s almonds. California almond growers rely exclusively on honey bees for crop pollination, which requires more than 1.8 million hives, or about two hives per acre.
More than half of all of the managed honey bee
colonies in the United States are required to pollinate
almonds every single year. The cost for commercial

pollination is about $300 million or about 10 percent of the total production costs for almonds. The cost to rent a single hive has increased from $15 to $30 to around $200 because the availability of colonies has become limited, the costs of maintaining the colonies has increased, and California growers have increased almond production. Ultimately, all of these factors are reflected in higher almond prices for consumers.
This is just a single example — there are dozens more with relevance for crops all over the world.
But there is more to honey bees than the services they provide, and understanding their remarkable biology is important to answer the question we posed at the beginning (Are honey bees in decline?). In the
sections that follow, we will explore the amazing and complex biology of this insect before discussing how some of the stressors (including pesticides) affect them.

Each year, beekeepers truck millions of bees to California’s Central Valley to pollinate almonds. © Smithers Viscient

A Marvel of Nature

Human civilization and honey bees have coexisted for thousands of years. As a direct benefit, honey bees provide us with products such as honey (a natural sweetener) and wax (for making candles and other products). Honey remains one of nature’s best and most versatile examples of a naturally produced product used in cooking, beverages, cosmetics, and medicines. Annual U.S. honey sales amount to $320 million. Americans consume 450 million pounds of honey each year, more than half of that honey is imported.
While honey is an important bee product, the greatest value of managed bees is in the pollination of nut, fruit, and vegetable crops. For example, commercial beekeepers transport tens of thousands of hives on semi-trucks to farms growing crops that require insect pollination. Bee managers transport hives to pollinate almonds in California; blueberries in Maine, Georgia, and Florida; cherries in Michigan; apples in Washington and New York; melons in Indiana; cranberries in Wisconsin; and sunflowers in North Dakota.

Some plants are self-pollinated (this includes most grains or oilseed crops, tomatoes, peppers, peas, peanuts, and citrus), and other plants are wind-pollinated (including corn, soybeans, walnuts, and pecans). But many flowering plants require insects to move pollen from male to female parts to produce a fruit, vegetable, or nut. A large percentage of the most colorful food items in the produce section of grocery stores must be pollinated by honey bees and other pollinators.
We are now learning that pollination by wild bee species also contributes
substantially to yields in some fruits and vegetables, including many types of melons, stone fruits, and berries. Bumble bees (Bombus species) are particularly well-suited for pollinating plants such as blueberries and tomatoes. Alkali bees (Nomia melanderi) and alfalfa leafcutter bees (Megachile rotundata) are important for pollinating alfalfa grown for seed.

A honey's color and taste are determined by the flowers in bloom.
Cucurbit crops (including pumpkins and cantaloupes) need honey bees to produce desirable fruit.

Add it all up, and honey bees and other pollinators are directly or indirectly responsible for one-third of the food Americans consume with an annual economic value of $19 billion. Without the commercial beekeeping industry and the pollination services the bees provide to agriculture, much of what we purchase at the grocery store would be far more difficult to find and considerably more expensive.
Worldwide, there are seven honey bee species, but Apis mellifera is the species hobbyists and commercial beekeepers use most often. The native range of A. mellifera is in Europe, and there are different

geographical races named after their respective areas of origin. These include the Italian, German Black, Caucasian, and Carniolan, many of which have become popular among beekeepers in the United States because of their specific rearing traits.
European settlers introduced the German black honey bee (Apis mellifera mellifera) to the United States in 1638. This specific race was well-adapted to cold temperatures.
In the 1850s, beekeepers imported the Italian honey bee (Apis mellifera liqustica), because it produced larger colonies, made more honey, was gentler and easier to manage.

The availability of many of fruits is tied directly to pollinators.
While honey bees are well-known pollinators, other insects are also important pollinators, including the bumble bee, alfalfa leafcutter bee, and alkali bee. © Smithers Viscient

Today, many apiaries typically include hybrids of these and other races. Although queen bees are sometimes artificially inseminated, the vast majority  of queens mate while flying with multiple males (drones), which results in diverse genetic mixtures and genetic diversity  in the hive. These genetic mixtures are hybrids that have different characteristics including disease resistance, foraging efficiency, aggressiveness, adaptability to fluctuating food availability, honey production, and cold-weather tolerance.
Scientists have long been fascinated with honey bees. The study of honey bee biology goes back as far as Aristotle (384-322 B.C.), making it one of the oldest subjects of scientific inquiry. And the economic

importance of honey bees for pollination and food production have made them the subject of work by research universities, the USDA, and many beekeepers and commodity organizations that have invested significant effort and money to study honey bee evolution, biology, genetics, foraging behavior, communication strategies, and management.
With the current suite of problems afflicting bees, this research is more crucial than ever. As a result of these concerns, we are learning more than ever about how bees live and work, and the factors that affect their populations.


Acting as One

Honey bees are social insects that live together in large numbers. This is in contrast to solitary bees (including sweat bees, leafcutter bees and others) and most other insects. In the case of solitary bees, the female is responsible for building the nest, collecting food, feeding the young, and defending the nest.
Honey bees evolved differently, and now large numbers of sterile female worker bees act as a “super organism,” that is, an individual bee is part of the larger social unit of the hive. A mated queen handles reproductive duties by laying eggs fertilized by sperm provided by male bees (drones) during the queen’s mating flight. While reproductive functions are important, it is the female workers (as sisters and daughters of the queen) who perform the majority of tasks inside and outside of the hive.
Honey bees cannot survive long on their own outside of the colony. Worker bees perform specific jobs based on their age.
Young adult workers perform in-hive tasks like feeding the larvae and queen, building wax combs, processing nectar into honey, keeping the hive cleaned, and guarding the colony.

As those adult workers age, their flight muscles develop to allow them to do out-of-hive tasks such as removing dead, dying, and diseased bees away from the colony, and, most importantly, foraging for pollen, nectar, water, and propolis. Propolis is resin from plants (including poplar trees) that honey bees use as a “bee glue” in the hive and as an antimicrobial medicine for the colony.
The oldest bees in the colony generally perform the most energetically demanding and dangerous work of foraging for pollen, scouting for forage areas, and finding new colony locations. Ultimately, these are a bee’s final jobs.
This division of labor among the adult workers is a model of efficiency, like a factory assembly line in which each worker has a defined and indispensable role. When a forager comes back with nectar, she does not deposit the nectar directly in a honey cell. Her priority is to get back to foraging. Instead, she passes the nectar to a receiver bee, who will then pass it along to others until it is placed in a cell. If the forager cannot find a receiver bee, she will buzz and recruit bees to become receivers. Once the forager bee has transferred the nectar to the receiver, she can immediately return to her duties finding more nectar and pollen.

Each female honey bee will assume many different roles inside and outside of the colony as she ages.

It Smells Like Home

Like other insects, bees sense odors (smell) with their antennae. Every colony has its unique chemical “signature” smell that allows the guard bees to recognize that the incoming foraging bees belong to that specific colony, and are not foreign bees seeking to rob honey.
Within a hive, the bees’ bodies secrete a hydrocarbon blend onto the bee’s surface. The hydrocarbon also picks up particular floral, wax, and propolis scents that set them apart from other bees in the area — even those bees that may be from an adjacent colony just a few feet away in a large apiary that contains thousands of hive boxes.

Foraging honey bees use sensory cues that allow them to return to the correct hive.

An Information Processing Center

With a workforce consisting of more than 40,000, it is imperative that a hive is able to clearly and rapidly communicate the needs of the group — the same is true even for smaller colonies of a few thousand bees. Given that the inside of the hive is dark, the only true way of communicating is by olfactory (smell) cues and vibrations.
Pheromones are chemicals that bees release and can detect with their antennae. The bees then react to the specific messages these compounds convey. Pheromones can communicate the presence of the queen (queen pheromone), the queen’s health, what
and when to feed developing larvae, and when an attacker is threatening the hive (alarm pheromone).

Returning foragers relay direction and distance information to other bees. This worker is vibrating so rapidly while performing the waggle dance that her body is a blur. © Scott Camazine
Bees transmit abstract messages to sister bees through the round dance and waggle dance. © Scott Camazine

Dancing for Direction

Like humans, honey bees have a symbolic language — bees use their famous “waggle dance” as a language. These dances allow a returning forager to communicate with its hive mates about the location (direction and distance) of pollen and nectar. Scientists have identified two different dance languages: the round dance and waggle dance, for which Karl von Frisch won a Nobel Prize in 1973.
The round dance happens when nectar and pollen resources are close to the hive (within about 100 feet). The forager bee will turn in circles alternating to the left and right. While this conveys the message that flowers are near, the round dance does not provide information about direction.
While dancing in a circle, the forager passes off small amounts of nectar to several different foragers. Not only can the newly recruited foragers taste the nectar, they also pick up the smell of the flowers from the forager’s body. Taste and smell are valuable forms of information that become a signature of what the foragers are searching for around the hive. Incidentally, this is the primary reason that flowers smell the way they do — while not all flowers are pleasing to humans, their various odors include a range of compounds that attract a diverse group of potential pollinators.
As the distance to the food source gets farther away from the hive, the round dance coalesces into the waggle dance. The waggle dance communicates information about both the distance and direction of the flowers.

Inside the darkness of the hive on a vertical comb, the returning forager who has information to convey will dance in a pattern close to a figure eight. On the vertical comb, the bees interpret the direction of the sun to be always at the top of the hive. So, if the source of the nectar is 90° to the left of the sun, the forager performing the waggle dance will orient her head in that direction with respect to straight up. Bees can tell which way is up using gravity and they can follow the dancer by feeling the wind of her buzzing wings. The foragers, responding to this information, will leave the hive at an angle of 90° to the left of the sun and travel in the general direction of the food source.
If the flowers are two miles from the colony, the bee will orient to the direction and vigorously shake and vibrate. If the food source is one mile away, she will shake and vibrate faster for a shorter duration than if it is two miles away. The length of time that the forager waggles conveys to the other workers how far away they will have to search.
The dance does not pinpoint exactly where the plant patch is, but it provides the general location of where to slow down and search. Once in the general vicinity, workers will rely on visual and olfactory cues to locate the flowers. The overall vigor and intensity of the dance is also a cue — it excites other bees when a forager is more animated — and will influence the numbers of foragers recruited.

Bees Remember

Amazingly, a forager remembers where she has been. She has a mental map in her brain that allows her to return to the same place she fed the day before and that allows her to find her home when she is done.
A honey bee’s compound eyes do not see with as much resolution as human eyes — researchers believe that what a bee sees is akin to a very crude pixelated image. But that doesn’t mean visual cues are unimportant. Bees can and do see, learn, and recall a variety of landmarks and cues, including floral smells, shapes, patterns, and colors. They are also very good at perceiving movement. As a bee gets closer to the flower patch, visual clues take over. Color (specifically ultraviolet (UV) light) is another very important cue. Her eyesight is good enough that when she is flying she can discriminate familiar but general shapes and patterns.

The Bee Factory Produces Bee Bread and Honey

Most organisms need a diverse diet consisting of minerals, carbohydrates (sugars), fats, and amino acids (proteins) to survive and reproduce. Honey bees get these essential nutrients from flowers. Nectar (produced by the glands of flowers to attract pollinators) is rich in sugar and becomes the bee’s main energy source. Flower pollen is the main source of amino acids that make up proteins (and some fats) that provide the building blocks in the bee’s body.
Honey bees are willing to eat fresh nectar (which has far more water and less sugar than honey) and pollen as it comes into the hive. However, altering nectar and pollen gives them flexibility in storing these products for those inevitable times when pollen and nectar become scarce in early spring and late fall.

This honey bee is heading out on a foraging trip. Note the fine hairs that cover the bee that make it effective at collecting pollen. © Alex Wild

Carbohydrates and Nectar

Honey is not just a repository of concentrated nectar. It is a manufactured product that uses nectar as the primary ingredient. The process of converting nectar into honey begins with the foragers.
Foraging bees lap up minute amounts of nectar from flower glands located at the base of the female portion of the flower or from extra-floral nectaries (depending on plant species). That foraging bee will digest some of that nectar for its own energy needs. But most of the nectar will remain in the bee’s honey stomach, an organ that is adapted for transporting nectar and bringing it back to the colony for eventual storage. The foraging bee visits flowers until she fills her honey stomach, and then either continues foraging until she has a full load of pollen or simply returns to the hive.
While the nectar is in the honey stomach, the enzyme called invertase begins to break the more complex sugars (such as sucrose) into glucose and fructose, which are easier for honey bees to digest (as well as for humans and other animals). Upon returning to the hive, the forager opens her mandibles and allows a receiver bee to suck out the regurgitated nectar. The forager usually transfers the nectar to two or more receivers who then place a drop of nectar into a cell. The process of exchanging food like this is called trophallaxis. During the process of transferring nectar from one receiver bee to another, the bees add other enzymes

to help break down the original nectar and stabilize it against degradation. Nectar is 60 to 80 percent water, depending on the plant species. Conversely, honey is less than 18 percent water — illustrating another way bees refine nectar. Honey’s lower water content helps preserve it. Worker bees remove the water by fanning their wings in the hive to evaporate as much water as possible, effectively acting as tiny dehydrators. Bees don’t fan their wings at each and every cell, but the passing of air throughout the hive helps evaporate the water.
Reducing the water content also increases honey’s sugar content, so it provides greater energy per unit volume than the more dilute nectar. Given that honey is the “high octane” fuel for the extremely active bees, the more concentrated the product, the more
energy and bang-for-the-buck that the bees obtain.
Removing the water from nectar is not the only way honey bees preserve nectar. They also add preservatives to prevent honey from spoiling. Like humans, bees must constantly battle the ubiquitous bacterial and fungal organisms that cause food to spoil. Honey bees add an enzyme called glucose oxidase (a type of oxygenase) to make honey mildly antiseptic and sterile. Glucose oxidase works at the honey’s surface where it combines with oxygen to turn glucose into gluconic acid and hydrogen peroxide.

This photo shows forager and receiver bees exchanging nectar. This food exchange is known as trophallaxis. © Alex Wild
This photo shows cells with nectar and bee bread.

Honey also has such a high concentration of sugar and such low water content that it draws moisture from any microorganism that lands in it. These features, combined with the fact that honey is acidic (with an average pH of 3.8), makes it highly unlikely that microorganisms can survive in this hostile environment.
Once bees fill a cell in their comb with honey, the bees build a wax cap over it. Over time, the cap turns darker as the air escapes. At this point, the cell is considered sealed, and the honey inside may remain edible and unspoiled for a very long time.

Darker cells are nearly devoid of oxygen and sealed.

Pollen from the anther, or male part of the flower, is a colony’s protein source. As bees fly, they become electrostatically-charged. As a result, when bees land on a flower, pollen literally “jumps” off the anther and attaches to the hairs on the bee’s body. These hairs are also branched, which helps hold pollen. This adaptation makes the business of collecting pollen easier.
However, bees must still considerably manipulate the plant structure to get enough pollen for a full load. As the bees work the flowers and collect the pollen on their bodies, they will brush pollen into a pollen basket (corbicula) found on the outside of her hind legs. Once a bee fills both baskets with pollen, she returns to the hive.

Foragers returning to the hive with pollen. Note that the bee at the top right has a full load of pollen in the pollen baskets on her hind legs.
These photos show bees with pollen baskets at different levels of fullness (from left): empty pollen basket, partially full pollen basket, and a full pollen basket.

Instead of passing pollen to other bees like they do with nectar, a foraging bee that returns to the hive with a loaded pollen basket will deposit her load somewhere near where young larvae are being raised. Young nurse bees are the principal consumers of stored pollen (called bee bread), which they feed to the larvae.
Bees also enzymatically process and age the bread. Other bees will pack the pollen into a cell. After the pollen forager has completed her task, she may consume some honey for energy and then return to the foraging site to retrieve more pollen.

Honey bees can eat pollen like they eat nectar, but pollen’s outer coating can be difficult to break down and digest. Young adult honey bees (nurse bees) turn pollen into a more easily digestible product called bee bread. Nurse bees digest bee bread in their guts, and then glands in their head (hypopharyngeal glands) use the digested protein to produce royal jelly or brood jelly. Older worker larvae are fed a mixture of chewed up pollen and diluted honey in addition to brood jelly; however, the queen is fed royal jelly throughout her life.

POLLEN PROCESSING A Versatile Foodstuff
After a foraging bee deposits pollen, another worker compresses it with her head to remove air spaces. The different colors indicate that the pollen is from different flowers. © Alex Wild

Saving for a Rainy or Cold Day

Bees store honey and pollen so the colony has food when flowers are in short supply, on rainy days when foraging activity is limited, or through the winter when the bees are clustered in the hive for months on end.
For an organism with a colonial life cycle and enormous energy needs, the ability to store food resources isessential. Without it, honey bees would periodically run out of food and starve to death.
We all know that during the spring and fall, flowers do not bloom on the same date each year. In fact, when flowers bloom can vary by weeks from year to year. This is why a hive needs thousands of foragers to take advantage of flowers when they are blooming. The next flush of flowers and weather are both unpredictable in timing and abundance, so gathering the products from flowers is critical when they are available.
The fall nectar flow is particularly variable from year to year. Honey bees depend heavily on the late-season rush of goldenrod, asters, and other plants in the fall. Many beekeepers usually harvest most of their honey in August and trust that the colony will collect additional nectar to get them through the winter. Most beekeepers will also supplement colonies with sugar water during this time. Still, this last flush of flowers is critical to provide the colony with enough stored honey to help them survive the winter.

purple aster with a bees collecting pollen pg 20
A variety of fall flowers, many of them asters, are necessary to help bees get through the winter with sufficient honey reserves.

Drinking at the Mud Hole

Honey bees gather minerals and a variety of salts from shallow and often stagnant water puddles. It sounds counter-intuitive, but the pristine and clear waters of a babbling brook are less appealing to honey bees. Bees prefer brackish and mucky waters because they contain a range of micronutrients not easily found during their visits to plants.

stagnant water-muddy puddle pg 21
Stagnant water can be rich in nutrients for the honey bee.

A Room with Six Walls

Each honey bee has glands on the lower side of its abdomen that secrete a clear liquid wax. After a few minutes, this material solidifies but remains pliable by chewing. Working the wax in their mouths, workers build the comb walls tilted slightly upward to keep the honey from flowing out of the cell.
Hexagonal cells are characteristic of a honey bee’s comb. A hexagonal cell with its six walls has been shown to be the most efficient way of using all the space available. The six-sided cell also maximizes strength, while minimizing the amount of wax needed for building the walls. When a frame is completely full of honey or pollen, it can weigh several pounds, and yet the hexagonal design doesn’t sag or stretch.
Bees must expend a lot of energy to produce wax. It takes eight ounces of honey combined with secretions from the bees themselves to make just a single ounce of wax. Beekeepers reuse and recycle all wax cells to reduce the
energy they must expend to make wax, which then allows the bees to store more honey. This is one of the reasons that commercial beekeepers are loathe to throw out old frames. To maintain a clean, healthy operation, it is sometimes necessary to throw out a frame, especially if disease, parasites, and pesticide contamination are suspected.

This photo shows a partially drawn out comb that reveals cells under construction.
A worker bee’s wax secretions result in solidified plates. © Scott Camazine

An Air-conditioned Hive

Honey bees require very specific temperatures inside the hive to protect their brood and food reserves. If the hive temperature gets too hot (this is common in the summer), foragers will collect water and bring the water back to the hive in their honey stomachs.
Foragers bringing water back to the colony transfer it to receiver bees who put small droplets into empty cells, or close to individual brood cells, but do not touch the larvae or eggs. Workers at the entrance will fan their wings to create air currents inside the hive that transfers the heat into the water, which is an evaporative cooling process.


Bees at the hive entrance move air by fanning their wings. When bees fan their wings at the hive entrance, it helps lower the temperature inside the hive. © Alex Wild

A Call to Arms

Honey bee colonies represent an incredibly rich and uncommon food resource. Pounds of honey and thousands of vulnerable and protein-rich larvae inside the hive make a tempting target for any animal brave enough to tear into it. Honey bees will aggressively defend the resources they have worked so hard to collect, process, and store because their future depends on them. In fact, the venom in their sting is a potent deterrent to many mammals, although it is sometimes insufficient to completely keep them at bay.
Workers known as guard bees defend the entrance against marauding insects and mammals that try to gain access to the hive’s contents. Marauders can include honey bees from other colonies (robber bees), many species of yellow jackets, as well as, mice, skunks, raccoons and bears. Honey bees must be particularly vigilant when foragers from other colonies attempt to rob honey after the last fall flowers have bloomed.
Guard bees defend the hive against insects such as wasps by biting and stinging them. Against larger invaders such as mice, honey bees rely on an accumulation of workers to sting the animal.
An adult honey bee worker has a serrated stinger, which is intended to lodge in its target. When a honey bee stings, it is a one-shot proposition (unlike wasps and many ants). The honey
bee loses its stinger and the venom gland from inside  its abdomen, then dies shortly afterward.
The embedded stinger continues to pump venom, appearing like a very tiny beating heart. But perhaps more importantly, it smears the area with an alarm pheromone that alerts other bees of immediate and impending danger, and it marks the spot for others to sting. That’s why one sting often leads to more in short order. If you’ve ever been stung by a bee and taken the time to observe the spot, you will see the gland on your skin. If you carefully scrape off the stinger and venom gland (as opposed to crushing or swatting at it), less venom will be pumped into the site of the sting.
Bees may have poor eyesight, but they have excellent olfactory (odor) perception, so they can track invaders even as they run away — if you have ever been chased by bees, you know this first-hand. The alarm pheromone recruits more members of the hive to come to the site of the “battle” and offer their assistance.


Bees standing guard at a hive entrance.
Invading or sick honey bees are killed and removed from the hive.

Airlifting the Dead, Deformed, Diseased, and Dying

It is common for dead, deformed, diseased, and dying bees to be found in or near a hive by other colony residents. A group of bees quickly identifies and drags these bees out of the colony — sometimes close to the entrance, but often farther away.

An undertaker bee transports a dead or dying bee away from the hive. Undertakers often fly off with dead or diseased bees.

The bees that do this job are called undertaker (or mortician) bees. Sometimes, undertaker bees actually pick up their dead sisters and fly away with them. They remove them from the hive for hygienic purposes — to get them away from the colony where healthy bees will not come in contact with them.
When dead bees are deposited at the entrance, they are often consumed by ants, yellow jackets, and other scavengers.

This wasp is preparing to take a dead bee to its colony.

Building and Maintaining a City of Wax

Beekeepers learned many centuries ago that bees could be housed in hollow logs, clay vessels, and woven-domed straw baskets (called skeps). The problem was that removing the wax and extracting the honey meant the container had to be destroyed, because the combs were haphazardly positioned within these containers. Inevitably, some combs with honey would go to waste.
So, for harvesting honey, the invention of the Langstroth hive, which was patented in 1852, was an important advance for beekeepers. Lorenzo Langstroth was a Philadelphia theologian who built a wooden honey bee hive with removable frames that was simple to assemble, inexpensive, and relied on materials that were portable and reusable.
Langstroth and others observed that honey bees filled in spaces that were either smaller or larger than the width of one bee. If the space was too small for the bees to pass through, they would seal the space with propolis. If the space was too large, the bees add comb to fill the larger space.
In either case, the frames become attached to one another, which prevented the beekeeper from readily pulling individual frames out of the hive. This optimum space became known as “bee space,” and when Langstroth built his hive, he made sure the frames were spaced apart by the width of one bee (3/8 inch), which allowed the frames to remain largely unattached to each other.

The spacing between each frame in a bee box is crucial to ensure that beekeepers can remove them easily.

The Langstroth hive’s many benefits include:

• Removable frames that allow beekeepers to easily harvest honey
• Reusable frames that allow honey bees to reuse the wax in their comb
• A scalable system that makes it easy for beekeepers to add boxes on top to provide bees more space to store honey
• A way for beekeepers to inspect bees without disrupting the colony
• A simple screen (called a queen excluder) that can be used between boxes to keep honey and brood frames separate
• The ability to fill frames with a healthy brood as “transplants” to start a new hive or reinforce a weaker hive
• A way to readily transport colonies from one location to another, which allows beekeepers to move bees from coast to coast for commercial pollination services
The Langstroth hive is largely unchanged from its original design. The adoption of the Langstroth hive is credited with creating the commercial bee industry and making it popular for hobbyists to raise honey bees.

Drawing Your Home’s Blueprint on a Foundation

Each wooden frame encloses a plastic or wax foundation. It is this vertical foundation that lets beekeepers control where the bees build their honey combs. Without the foundation, bees will build combs in whatever direction that makes use of the available space, which means beekeepers could not remove each frame without damaging the combs. An additional advantage of using a plastic or wax foundation is that it gives the comb structural stability and support when filled with honey.

A wax-coated plastic foundation.

Drawing Your Home’s Blueprint
on a Foundation

The bottom board provides a landing pad and an entrance-exit from the hive. It also provides a platform for bees to ventilate the hive during the hottest days of the year.
You can think of the brood box as the hive’s nursery. It consists of one or more boxes where the queen lays eggs and workers feed developing larvae. Beekeepers do not harvest any honey from the frames in the brood boxes.

Queen Excluder

The metal or plastic queen excluder prevents the queen from leaving the brood box to lay eggs in the upper supers. The frame is wide enough for workers to pass through, but not the queen.


Honey supers are boxes similar to brood boxes, but are typically shorter.
Each super holds nine to 10 frames to store
excess honey. As bees fill each super, beekeepers add more supers. Beekeepers harvest honey from the supers — each weighs 35 to 40 pounds when filled with honey.

Inner Cover

The inner cover is the hive’s ceiling. An elliptical hole in the center provides ventilation. The inner cover provides the proper bee space so bees do not glue it to the outer cover with propolis.

Outer Cover

The outer cover is the roof that protects the colony from rain and snow.


Beekeepers use smoke to disarm the guards who recruit bees to sting. The light smoke masks the alarm pheromone, so fewer bees are recruited to sting. It also induces the bees to engorge themselves with honey, which makes them more docile and less likely to sting.

A healthy colony averages between 20,000 to 60,000 honey bees, but these estimates vary depending on the availability of nectar and pollen, time of year, and health of the colony. Within the colony, honey bees are divided into three biologically and physiologically distinct adult castes:

1. A single reproductive female known as the queen
2. Several hundred to a thousand reproductive males called drones
3. Thousands of sterile female workers

While there are differences between the three castes, each passes through the same phases of development: egg, five larval stages (each stage is called an instar), a pupal stage, and adult. The number of days to go from an egg to an adult varies by caste.


Honey bees have distinct castes. The much longer abdomen of the queen differentiates her from other females in the colony. Drones (males) are characterized by larger compound eyes that meet up at the top of the head.