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Found in Translation

An Interview with Dr. Hongmei Li-Byarlay
Associate Professor and Project Director for Pollinator Health, Central State University, Ohio
By: Jay Evans, USDA Beltsville Bee Lab

Where are you from originally?
*I was born in Tianjin, China, and came to the U.S. to study for my Ph.D. in 2002.

How did you get interested in science?
*When I was a sixth-grader, I talked to my uncle and told him that I want to be a scientist! Maybe because I had read so many books on the weird creatures in the deep ocean and stories of UFOs.

Where did you go to school and what did you study?
*I went to Tianjin Normal University for my Bachelor’s degree in Biology and Education (dual degree). My senior project was on the effects of metal contamination on bacteria in garlic roots. Then, I went to Nan Kai University for my Master’s degree in Zoology. I studied micro-moths in Northern China and discovered four new species.
In 2002, I went to Purdue University in Indiana for my Ph.D. in Entomology and studied genetics and physiology of fruit flies with Dr. Barry Pittendrigh and Larry Murdock. In 2010, I started my postdoc training with Dr. Gene Robinson at the University of Illinois at Urbana-Champaign, studying behavioral genetics of honey bees. In 2013, I studied epigenetics and aging of honey bees with Drs. David Tarpy at NCSU and Olav Rueppell at UNC-Greensboro.

How did you start your career after school?
*In 2017, I got an offer from Central State University as a new Assistant Professor of Entomology. CSU had just gained their new status as a 1890 Land Grant Institution with USDA. I was very excited to start my own lab.

Which hot topics are you studying now?
*I am studying 1) the molecular and physiological mechanisms underlying the social behavior and ageing of honey bees, such as grooming behavior, aggression and foraging behavior, 2) active breeding efforts for selection of mite-resistant bees by selecting mite-biting stocks and 3) landscape ecology of pollinators and flowers.

Where have you traveled in your studies of bees and what was most memorable?
*I have traveled to China, Germany, Canada, Puerto Rico and many different states in the U.S. The most striking memories were observing and doing experiments with Apis cerana in China, and my trip to Puerto Rico to see and feel the gentle AHBs in reality. I really enjoyed interacting with all the hives there.

What are the biggest challenges facing beekeepers moving forward?
*The desire to find new solutions for mite management is so high, and there are many new ideas. I just hope we all think of new solutions by integrating the sustainability of our hives and our environment.

What gives you hope? What are the best recent discoveries in bee science?
*The government, bee scientists, beekeepers and non-profit organizations are all working together to find the best ways to help our bees, which showed the most love and funding support from the community.
Three of the most interesting discoveries from our lab are:
1)A new publication on Single-cell dissection of aggression in honey bee colonies. https://www.nature.com/articles/s41559-023-02090-0. We are all so excited to use a new sequencing technology to help us to understand bees in a deeper way.
2)Our lab’s new pub about RNA methylation and discovery of long non-coding RNAs underlying bee aggression https://bmcgenomics.biomedcentral.com/articles/10.1186/s12864-023-09411-4
3)We showed that the mandibles (mouthparts) are different between high mite-biting honey bee workers and current commercial colonies. I am also working on a new manuscript to show the striking comparison of mouthparts between two different species of Apis, in hopes this sheds light on mite defenses. https://doi.org/10.3389/fevo.2021.638308

Any advice for future scientists?
*Stay curious and ask questions!

What are your hobbies and other interests beyond bees and science?
*I like running, reading with my kids, hiking and camping in national parks, and meditation.

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Found in Translation

An Egg-Level View of Drone Production
By: Jay Evans, USDA Beltsville Bee Lab

Honey bee males, or drones, are belittled but key members of the colony. They also form a test case for one of the most fundamental questions in animals and plants. When there is a distinction between males and females, how does that come about? In bees, as in many other species, development into males or females is not black and white. There are proteins (or in cases like our own species, entire chromosomes) that help set the stage for a cascade of events that determines sex. Most of the time, a single trigger, or ‘sex-determining factor’, starts the male and female cascades, and these cascades generally result in physically different males and females. Both that trigger and the resulting cascade differ across the tree of life, and it is hard to point to common sex-determining factors across the insects, let alone the cascades that generate distinct males and females more generally. Thus, it was a really big deal 20 years ago when a research group in Germany led by Martin Beye won the race to find a plausible sex-determining factor for honey bees (M. Beye, M. Hasselmann, M. K. Fondrk, R. E. Page, S.W. Omholt, 2003. The gene csd is the primary signal for sexual development in the honey bee and encodes an SR-type protein Cell 114, 419–429, https://doi.org/10.1016/S0092-8674(03)00606-8). Just this month, that same group closed the circle by demonstrating the key mechanisms by which this factor kicks off drone versus female production in bees… but first some background.

It is staggering to realize that a European priest, Johann Dzierzon, accurately described the process that leads to male honey bees 180 years ago. He was able to show, experimentally, that queens which had been prevented from mating were exclusively drone layers. Genes were not a thing then, let alone sex-determining genes, but genetics was soon to be a field, and there is evidence that Dzierzon’s insights and experiments helped trigger the appreciation for how genetic variation leads to the diversity we see within species. Dzierzon’s passions included how worker bee body colors reflected both queens and their mates and his careful work likely planted seeds in the mind of fellow priest and apiarist Gregor Mendel, who was starting to conduct the pea breeding experiments that defined his own legacy. A nice recent review by Gene Kritsky builds the case for Mendel’s likely exposure to Dzierzon’s thinking in science circles of the 1850’s and 60’s (Kritsky, G. Bees and Peas: How apiology influenced Gregor Mendel’s research. 2023. American Entomologist, 69, 40-45, doi:10.1093/ae/tmad025). Mendel did not formally acknowledge the assist, and it is unclear whether he would have reached the same conclusions and experiments solo. What is certain is that Dzierzon got pretty much everything correct about honey bee reproduction, marveling at queen nuptial flights and the abilities of queens to take or leave sperm from those flights as they nurtured their developing eggs, “The power of the fertile queen, accordingly, to lay worker or drone eggs at pleasure is rendered very easy of explanation by the fact that the drone eggs require no impregnation, but bring the germ of life with them out of the ovary; whilst otherwise it would be inexplicable and incredible. Thus the queen has it in her power to deposit an egg just as it comes from the ovary, and as the unfecundated mothers lay it; or by the action of the seminal receptacle, past which it must glide, to invest it with a higher degree, a higher potency, of fertility and awaken in it the germ of a more perfect being, namely a queen or a worker bee.”

So, how does recent research close the deal for honey bee sex determination? It was evident that the complementary sex determination (csd) gene identified by Beye and colleagues had a highly variable stretch that shows maybe 20 sequence variants in a given population and 100 overall in the species. If diploid female bees are many hundred-fold more frequent than diploid males (which are generally removed by their sisters during development), a gene with this amount of variation fits the bill as the trigger for sex, but how does it all work? Marianne Otte and colleagues from the Beye lab used several genetic tricks to show that a mismatch for this one gene between two chromosomes is both necessary and sufficient to generate female bees. They used ‘CRISPR’ gene editing of fertilized eggs to nullify sections of that variable region. When this happened, bees that would have developed into females were male. They also inserted a polymorphism into drone-layer queens and those queens then produced viable females. Basically, matches for a tiny region of this one protein were sufficient to bind the protein in ways that changed its effects on the next proteins in the cascade and altered the sex of these bees (see graphic). If one of those amino acids was mismatched between the two gene copies, the resulting poor binding led to a female cascade. That’s a simple mechanism for letting a single gene impact sex determination.

While csd appears to be unique to certain insects with haploid males (bees, wasps, ants in particular), it shows a historical similarity to ‘transformer’ proteins, which are known as key actors in insects with diploid males and females and sex chromosomes (i.e., with sex determination that is more like our own). How the leap was made from traditional sex chromosomes to species with haploid males is another mystery. In a practical sense, researchers are rapidly determining variation at csd across populations at all sizes. There is a cost to colonies when queens are mated to males with matching csd alleles. Even though many such ‘diploid males’ are purged early in development the initial effort to raise them, and patchy brood patterns, can both weigh colonies down. Knowing the exact mechanism by which variation works at this locus allows for accurate screens of breeding stock and larger commercial apiaries to see where adding fresh genes might improve productivity. It’s also really neat to think that every cell of a worker bee (or queen) in your colony carries a tiny genetic difference at one of the thousands of her proteins that defines her life.

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Found in Translation

Dog v. Machine: Identifying the Foul in Foulbrood
By: Jay Evans, USDA Beltsville Bee Lab

American foulbrood has been a consistent, if fortunately rare, curse of beekeepers for centuries. The bacterial agent behind AFB, Paenibacillus larvae, is widespread in managed colonies and yet only rarely triggers symptoms in the form of decayed and highly contagious infected brood. Catching those symptomatic cases early remains a critical goal of bee health management. Many U.S. states benefit from a cadre of bee inspectors who work with beekeepers to identify and act upon AFB infections (e.g., the Apiary Inspectors of America, https://apiaryinspectors.org/). Our own USDA Bee Disease Diagnostics Service, led by Samuel Abban (https://www.ars.usda.gov/northeast-area/beltsville-md-barc/beltsville-agricultural-research-center/bee-research-laboratory/docs/bee-disease-diagnosis-service/), works collaboratively with these inspectors and individual beekeepers to pounce on suspected AFB cases before their damaging shadow increases. While the visual and culturing tools for confirming AFB infections are robust, and that smell is hard to forget, there remains a huge need to rapidly screen apiaries for early signs of infection. The frontiers for this screening are marked by an unlikely pairing of furred partners and incredibly complex machines, and it is worthwhile to see which of these tools will be the most helpful for inspectors and beekeepers.

Starting with the more charismatic tools, trained dogs are sporadically used to help inspectors pin down cases of AFB. The state of Maryland has two such trained dogs, led by Chief Apiary Inspector Cybil Preston (https://www.earthisland.org/journal/index.php/articles/entry/detective-dog-sniffs-out-devastating-honeybee-disease/). These companions certainly have the sensitivity to identify signals given off by diseased brood, but how accurate are dogs with the critical early-stage cases of AFB? A study by Neroli Thomson and colleagues in New Zealand aimed to push the limits of training and detection by dog detectives (Thomson, N.; Taylor, M.; Gifford, P.; Sainsbury, J.; Cross, S. (2023) Recognition of an Odour Pattern from Paenibacillus larvae Spore Samples by Trained Detection Dogs. Animals: 13, 154. https://doi.org/10.3390/ani13010154). Two out of three trained dogs did great, consistently and quickly responding to AFB cues placed in one spot within a twirling carousel of dog dishes (Figure). These dogs were trained using purified spores, so would presumably do great even with empty boxes containing post-AFB scale. Their sensitivity in the indoor arena was at the level of spores found in a fraction of a single infected bee. What needs to be tested is the ability of these dogs to ignore the many other smells coming from a beehive, not to mention the environmental distractions (from stinging bees to nervous beekeepers) they would experience when truly on the job.

Since it is hard to interview a dog to find out the cues they use to detect AFB, I decided to explore the most recent work involving chemical sniffers that separate AFB smells from the large and shifting bouquet that is a beehive. Jessica Bikraun from the University of Western Australia devoted her PhD thesis to this question and already has one peer-reviewed paper showing the power of a machine detective approach (Bikaun, J.M.; Bates, T.; Bollen, M.; Flematti, G.R.; Melonek, J.; Praveen, P.; Grassl, J. (2022) Volatile biomarkers for non-invasive detection of American foulbrood, a threat to honey bee pollination services. Science of The Total Environment, 845, 157123, doi:https://doi.org/10.1016/j.scitotenv.2022.157123). Using readily available Solid phase microextraction (SPME) ‘wands’ as noses, she and colleagues collected air samples wafting from infected larvae in a lab-rearing setup and from larvae embedded in living colonies. Larvae sampled in the lab released 102 identifiable chemicals in the air around them. Of these, 17 were found only in larvae infected with the AFB bacterium, others were common to all bees (they also tested bees with sacbrood and bees that had been killed by freezing, along with healthy controls). How do smells in the pristine lab setting compare to those in actual colonies? The SPME technique, while inexpensive and widely available, is compromised somewhat by the greediness of the SPME noses. If there are overwhelming smells coming from a hive, those molecules might edge out rare diagnostic signals. Field trials identified 116 volatile chemicals from beehives, 17 of which were tied to disease. In the end, only four molecules (2,5-dimethylpyrazine, acetamide, isobutyramide, and methyl 3-methyl-2-oxopentanoate) were indicative of AFB both in lab-cultured bees and in-hive air samples. These four chemicals might form the basis for an accurate and simple test. They are also themselves interesting for possible insights into the disease itself. 2,5-dimethylpyrazine is tagged an agent used by bacteria for inhibiting the growth of other microbes, something P. larvae does exceedingly well. While the research was focused on cues that machines can identify, the team also found candidates for smells that hygienic bees pick up on when scanning for diseased brood. Lactones, for example, are natural compounds found in fruits and elsewhere that are often used as components for food additives. In the airspace of beehives, lactones increased substantially with almost any form of brood stress, from AFB to sacbrood and freeze-killed brood, and the authors suggest these compounds might be another trigger for hygienic responses by nest bees. Sujin Lee and colleagues used a lab-based assay to identify and reconfirm volatile chemicals emitted by larvae suffering from AFB (Lee, S.; Lim, S.; Choi, Y.-S.; Lee, M.-l.; Kwon, H.W. (2022) Volatile disease markers of American foulbrood-infected larvae in Apis mellifera. Journal of Insect Physiology, 122, 104040, doi:https://doi.org/10.1016/j.jinsphys.2020.104040. They then purchased those same chemicals to test for responsiveness by worker bees. Bees reacted to several of the candidates but the authors feel that propionic acid, valeric acid, and 2-nonanone were the cleanest signals of AFB infection. Younger bees reacted more strongly to these smells than did foragers, arguably reflecting the tendency of these younger bees (middle-aged actually) to act as hygienic helpers in the colony.

Both dog noses and artificial noses were shown to be capable of identifying even low levels of AFB in field colonies. The SPME chemical nose seems to have more promise as a consistent service (inspectors could readily collect smells from hives with a SPME wand and then send that wand to an analytical lab) but it would not give the in-the-moment diagnostic provided by dogs and good inspectors. For now, those live inspectors are earning their kibble by advising beekeepers when a problem is likely.

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Found in Translation

Mite Drop!
By: Jay Evans, USDA Beltsville Bee Lab

Varroa mites remain the primary source of honey bee colony losses for beekeepers managing from one to 10,000 colonies. Scientists like us and ardent beekeepers are always on the hunt for new ways to reduce varroa damage to bees and their colonies. One intriguing strategy is to make mites simply fall off their adult bee hosts. Short of changing the electric charge of host or parasite, this repellency can come from 1) making hosts less grippy, 2) somehow clogging the incredibly strong tarsi (feet with ‘toes’ and a spongy, oily, arolia) of mites or 3) affecting mite behavior by making them less likely to find safe spots and hang on to their bees for dear life. Dislodged mites are far more vulnerable to hygienic worker bees and might also simply keep falling down to a hostless, hungry and hopefully, short life. This is probably a central reason that female varroa mites spend very little time wandering the combs of beehives unless they are moments away from entering the brood cell of a developing bee. While on adult bees, mites have much incentive to stay right there, whatever their host is doing to drop them.

How do mites adhere to their bees so strongly? When mites are actively feeding on bees they are extremely hard to dislodge, since they are partly under the hardened plates of the bee itself and are gripping with a combination of ‘teeth’ and tarsi. Even while taking a break from feeding, mites know to find safe spots on the bee to attach, favoring locations on the abdomen or thorax that are both hairy and away from swinging legs and biting bee mandibles. How can one make them quit their bees given so many hiding places?

Caroline Vilarem and colleagues in France recently described an ambitious attempt to document the abilities of mites to hang onto surfaces when exposed to organic acids (Vilarem, C.; Piou, V.; Blanchard, S.; Vogelweith, F.; Vétillard, A. Lose Your Grip: Challenging Varroa destructor Host Attachment with Tartaric, Lactic, Formic, and Citric Acids, Appl. Sci. 2023, 13, 9085. https://doi.org/10.3390/app13169085). These scientists deployed one of the coolest low-tech tools to measure how well mites grip onto a surface. While their ‘Rotavar’ sounds both complex and expensive, it is actually a ‘motor-driven rotating toothpick’. Yes, you can do this at home, with a slow (three or so revolutions per minute) motor and a supply of toothpicks. The authors add to that an extremely careful experimental design and complex statistics to show the different abilities of mites to hang onto sticks and bees coated with acetic, citric, lactic, formic and tartaric acids. The results hint at new modes and new candidates for mite control, with the usual caveat that converting a controlled lab assay to field colonies will be challenging.

Schematic diagram of the experimental design and measured parameters. Grip on wood (Rotavar): This method relies on direct contact between Varroa’s arolia and the organic acids. The Rotavar set-up is a motor-driven rotating toothpick used to assess V. destructor’s grip. Grip on bees: the host attachment experiment applies acids to the backs of honey bees to remove mites. T0 represents the administration time for treatments; T + 1 h 30, 24 h, 48 h, or 72 h stand for the time post administration used to make measurements. Figure from https://doi.org/10.3390/app13169085

Some highlights: First, acidity itself does not seem to be the solution. Most notably, even high doses of acetic acid had little impact on the abilities of mites to grab toothpicks and this candidate was quickly discarded. So, what can we glean from the differences between the tested acids? Tartaric acid worked great at dislodging mites from spinning toothpicks but was surprisingly poor at dislodging mites from bees. Prior work suggests that the mode of action for tartaric acid is, at least in part, toxicity towards mites. It is possible that the levels of tartaric acid needed to coat bees with a toxic dose are higher than they are on a relatively smooth and barren toothpick. Toothpicks also attract watery compounds (hydrophilic) while bees are coated with oils and are hence more water-repellent (hydrophobic). Maybe the availability of tartaric acid on toothpicks is higher than it would be on oilier bee bodies. Formic acid also worked much better on the wood surface than on bees, an intriguing insight for a well-used and effective mite control. Formic acid is also known to be directly toxic to mites and their cells, and the authors make clear that both direct toxicity and grippiness are clear and perhaps synergistic targets for mite control. The widely used miticide oxalic acid also wins by being directly toxic to mites at levels that are relatively safe for bees, demonstrating that there are many possible ways to turn organic acids into effective treatments.

Lactic acid came out as the best candidate in the study group for divorcing mites from their bees. This acid worked well at dislodging mites from both toothpicks and bees. Lactic acid does not appear to be highly toxic to mites and instead seems to act by changing the mechanics of hanging on. This is a nice lead for exploring acids with similar qualities for their abilities to both grease the ‘Rotavar’ and make bees a more slippery host. In another intriguing result from this nice study, mites that simply walked across paper holding lactic acid were then less good in future grip tests. What is it about lactic acid that burns, cleans or otherwise insults the complex and surprisingly ‘soft’ tarsi of mites?

If this topic has gripped you, consider reading up on the field thanks to a recent open-access paper on stickiness by graduate student Luc van den Boogaart and colleagues in the Netherlands (van den Boogaart, L.M.; Langowski, J.K.A.; Amador, G.J. Studying Stickiness: Methods, Trade-Offs, and Perspectives in Measuring Reversible Biological Adhesion and Friction. Biomimetics 2022, 7, 134; https://www.mdpi.com/2313-7673/7/3/134). For those of us who have stored ‘Freshman Physics’ in a remote hard drive, they give a clear review of how these forces work across organisms; in their words ‘from ticks to tree frogs’. Maybe their figures and insights will inspire a beekeeper or scientist to dream up a safe, effective route to dislodge mites from bees and prevent them from climbing back on. Pulling in people with a knowledge of physics, or just really good imaginations and the ability to build and deploy Rotavars (imagine how entertaining those can be, a la squirrel spinners… https://www.youtube.com/shorts/nBKb_z4_tGY), can only help in the hunt for new mite controls and healthier bees.

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Sweet and Sour Honey
By: Jay Evans, USDA Beltsville Bee Lab

There are many ways that honey bees improve our diets but honey consumption was an early reason to wrangle this species. The taste for honey persists today around the world, sustaining sideliners, families and large corporations in many parts of the world. It is also widely known to soothe and improve relations with neighbors, in-laws and bosses. With any high-value product, there is a risk of inadvertent or purposeful false advertising.

One honey quality trait that is easy to control is water content. Small-scale beekeepers routinely put their honey crops and relationships at risk by bottling honey that hasn’t been fully processed by bees to a net water percentage under 19%. Watery honey both feels weird and is prone to unintended fermentation. Choosing properly capped frames goes a long way to eliminating this problem. If you live in a humid place like Maryland, there is also some risk that open honey will dehumidify some of the local air, pushing water content back above dangerous levels. Truly dry honey can be achieved by technique and awareness, but if you are curious and want to directly assess the water content of your crop, Hanna Bäckmo gives a nice review of the styles and costs of refractometers used by beekeepers in this magazine (https://www.beeculture.com/refractometer/). Certainly, steady honey producers would benefit from investing in, and calibrating, these things.

A bit out of reach for most of us, but essential for the industry, are lab-based assays aimed at confirming honey purity. The methods used for this continue to improve, putting clumsy or sneaky honey producers on notice. Notably, honey yields can be stretched by a variety of refined or expelled sugars. This might be inadvertent, when syrup fed by beekeepers in the Fall for Winter survival lingers, capped until Spring. There is no easy answer to this, certainly not from me, but step one is to get bees through Winter safely, and then assess any remaining capped stores to see if these stores are bona fide honey or syrup that bees dried down but didn’t gobble up as it came in. Ask a beekeeper near you for help.

Photo by Meggyn Pomerleau on Unsplash

More insidiously, producers or packers might outright add less expensive fillers to their honey, increasing yields but losing some of the magic of honey. The technology used to detect such adulteration is improving, and several techniques are now used by regulators, producers and packers to make sure honey is pure. The International Honey Commission described forensic methods for honey purity nearly 30 years ago and updated these methods in 2009 (https://www.bee-hexagon.net/english/network/publications-by-the-ihc/). The U.S. Food and Drug Administration, keeping honest folks honest across the industry, regularly tests new methods against imported and domestic honey to identify so-called ‘economically motivated adulteration’. Using a well-established technique, Stable Carbon Isotope Ratio Analysis (SCIRA), the FDA recently screened bulk and bottled honey samples from eight countries whose honey is imported into the U.S. (https://www.fda.gov/food/economically-motivated-adulteration-food-fraud/fy2122-sample-collection-and-analysis-imported-honey-economically-motivated-adulteration). This test distinguishes ‘C4’ plant sources (largely grasses and grains) from ‘C3’ sources (all the plants with prettier, bee-visited, nectar-rich flowers). The test simply asks if the unexpected C4-sugars, often from corn syrup or sugar cane, are over-represented in honey. There is some tolerance of these C4 sugars due to bee management or assay imprecision but that level is quite low, maybe 7% by volume. Each country in the FDA screen had at least one suspicious honey batch, but the overall frequency of such batches was 10%, a level roughly similar to a much larger recent study in Europe and indicative that honey, by and large, is as advertised.

There are several newer techniques in play now for the high-stakes race between regulators and those who might diminish the reputation of honey. Dilpreet Singh Brar and colleagues in A comprehensive review on unethical honey: Validation by emerging techniques (Food Control 2023, 145, 109482, https://doi.org/10.1016/j.foodcont.2022.109482) describe nearly 50 ways to test your clover. Within the alphabet soup of available methods, they reveal six chromatographic platforms (basically methods to separate parts of a whole by size, electric charge or affinity to some sort of ‘bait’) with increasing sophistication. These machines should put fear in anyone whose honey is not perfectly sound.

As a geneticist, I am fascinated with so-called environmental DNA (eDNA) screens, whereby a complex soup is scrutinized for the genomes of the diverse organisms floating in it. Many will remember the application of eDNA screens worldwide to identify levels and variants of the SARS-Cov-2 virus in city and town wastewater systems (poor interns!; https://www.nih.gov/news-events/nih-research-matters/tracking-sars-cov-2-variants-wastewater). This same methodology is now widely used to confirm the botanical sources of honey, the genotypes of the bees collecting that honey and the myriad of other organisms from the hive environment. Practically, this method also precisely identifies any honey contaminant with a biological source, from corn syrup to diverse flower sources mixed in accidentally in coveted monofloral honeys. It is also a sensitive assay for honey bee disease agents.

For the past 20 years, genetic analyses of honey from hives have been used to confirm the presence of the bacterium responsible for American Foulbrood, Paenibacillus larvae. Federico Lauro and colleagues in Rapid detection of Paenibacillus larvae from honey and hive samples with a novel nested PCR protocol (International Journal of Food Microbiology 2003, 81, 195-201, https://doi.org/10.1016/S0168-1605(02)00257-X) showed the value of this technique for keeping track of non-symptomatic P. larvae populations. More broadly, Leigh Boardman and others have confirmed that this technique can provide a snapshot of the whole range of microbes found in colonies (Boardman, L., P. Marcelino, J. A., Valentin, R. E., Boncristiani, H., Standley, J. M., & Ellis, J. D. Novel eDNA approaches to monitor Western honey bee (Apis mellifera L.) microbial and arthropod communities. Environmental DNA. 2023; https://doi.org/10.1002/edn3.419). Here, colony-collected honey is analogous to the worker-bee samples now used in many disease surveys. Honey collections have the added value of pointing out long-ago arrivals, providing a sort of fossil record for the plants and other organisms a colony might have come into contact with during the past year. The genetic methods behind these screens are astoundingly sensitive (remember, viruses floating alone in tons of sewer sludge) and honey or hive-based screens have promise for anything from virus outbreaks to the detection of newly invasive mites and other pests. It is incredibly hard to pass through an environment without shedding a little DNA, and a little goes a long way for these sensitive methods.

Economically motivated adulteration is detectable with some effort and that’s a good thing for all of us. Honey screening, especially with the twist of identifying genetic signals from hive organisms, is also becoming a nice tool for scientists keen on monitoring disease, plant sources and the genes of the bees that did all the work.

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Gut Microbes Help Bees Survive the Season
By: Jay Evans, USDA Beltsville Bee Lab

It will surprise most Bee Culture readers that microbes come in flavors that can be good, bad or indifferent to the health of their honey bee hosts. As we approach Fall, it is tempting to focus on the microbes on the good side and try to find out how to feed them for bee health prior to Winter. As someone who studies honey bee disease, I can’t help but focus on the good microbes that might interfere with agents of harm lurking in our beehives.

Kirk Anderson and colleagues in the USDA’s Tucson Carl Hayden Bee Research Laboratory have been exploring the impacts of gut microbes on bee health for a decade now. In past work, they showed how these microbes are beneficial in the guts of bees but generally ‘don’t’ help in the processing of pollen stored as bee bread. They have also shown how queens and workers differ greatly in the microbes they harbor and the impacts of bee contact on moving microbes around (see Anderson’s ‘Google Scholar’ profile for lists of his papers on these topics; https://scholar.google.com/citations?user=JiEFFkIAAAAJ&hl=en&oi=ao).

They have also explored how bees suffer mortality when the delicate microbial balance is upset. Recently, they have investigated honey bee overwintering, testing for the right mixes of nutrition and temperature that improve the odds of colony survival (hint: cold is good, to a certain degree). In a paper this past year, they describe how the gut microbes of bees react before and during Winter, building the case that microbes are critical for overwintering success (Anderson, K.E.; Maes, P. Social microbiota and social gland gene expression of worker honey bees by age and climate. Scientific Reports 2022, 12, 10690, doi:10.1038/s41598-022-14442-0).

They also show that the overwintering environment can favor certain microbes that are less helpful for bee health. Specifically, bee colonies overwintered in a warm environment started with the typical population of gut bacteria but that population broke bad in the end, notably thanks to overgrowth (these were NOT found in bees) as well as several types which ARE known to decrease bee health. Just what it is about warmer Winter environments that favors an odd, and apparently harmful, bacterial group is not known, and solving this will be key in future work aimed at prepping bees for current or future Winter climates.

More generally, disease agents are opportunists; taking advantage of their victims when something else is out of whack. These opportunities can arise from stressors in the environment, poor genetics or inadequate nutrition. Opportunities might also arise when populations of good bacteria are somehow absent. There are a myriad of ways that such ‘good’ microbes could help bees in the face of disease, from providing a physical layer on the gut wall that frustrates pathogens, to improving nutrient transfer or stimulating bee immunity.

Finally, gut microbes might directly attack the bad actors. Studies showing increased honey bee disease following heavy antibiotic treatments provide ample evidence for the roles of natural bee bacteria. In one such study, led by Jiang Hong Li and my USDA colleague Judy Chen (Li, J.H.; Evans, J.D.; Li, W.F.; Zhao, Y.Z.; DeGrandi-Hoffman, G.; Huang, S.K.; Li, Z.G.; Hamilton, M.; Chen, Y.P. New evidence showing that the destruction of gut bacteria by antibiotic treatment could increase the honey bee’s vulnerability to Nosema infection. PloS one 2017, 12, e0187505, doi:10.1371/journal.pone.0187505). Gut microbes were shown to help bees resist nosema disease. A cleansing of gut bacteria by an intensive antibiotic regime resulted in shorter lifespans overall, and increased the impacts of nosema exposure on longevity.

Sean Leonard and colleagues, in the University of Texas laboratory of Nancy Moran, showed that a human assist can further sharpen the impacts of natural gut microbes on bee parasites. Specifically, they engineered (in the laboratory) a common ‘good’ bacterium of bees so that it targeted challenges as distinct as Varroa mites and Deformed wing virus (Leonard, S.P.; Powell, J.E.; Perutka, J.; Geng, P.; Heckmann, L.C.; Horak, R.D.; Davies, B.W.; Ellington, A.D.; Barrick, J.E.; Moran, N.A. Engineered symbionts activate honey bee immunity and limit pathogens. Science 2020, 367, 573-576, doi:10.1126/science.aax9039).

Nosema. Credit: Qiang Huang

Work this year based on the same strategy (led by Qiang Huang from Jiangxi University, working in Moran’s lab) showed resident bacteria could be altered to successfully target nosema disease (Huang, Q.; Lariviere, P.J.; Powell, J.E.; Moran, N.A. Engineered gut symbiont inhibits microsporidian parasite and improves honey bee survival. Proceedings of the National Academy of Sciences 2023, 120, e2220922120, doi:10.1073/pnas.2220922120). Bees with the engineered bacteria both lived significantly longer and had far fewer nosema spores to pass on to their nestmates. Interestingly, bees fed the gut bacterium alone, and the bacterium with a nonspecific (not targeting nosema), modification also showed signs of reducing disease impacts, supporting the evidence that the bacterium itself is also a friend to bees.

Short of this high-tech solution, are there ways that beekeepers can help nurture the natural gut bacteria found in their beehives? If you supplement your bees, a recent paper by Elijah Powell and others in Moran’s group suggests that pollen-based supplements tend to lead to a more balanced ‘core’ set of bacteria in the bee gut, possibly decreasing the threats from at least one bacterial pathogen of adult bees (Powell JE, Lau P, Rangel J, Arnott R, De Jong T, Moran NA (2023) The microbiome and gene expression of honey bee workers are affected by a diet containing pollen substitutes. PLoS ONE 18(5): e0286070. https://doi.org/10.1371/journal.pone.0286070). I know there are many colony supplements available and I don’t claim this makes a pollen-based supplement better for bees overall than supplements with a different protein source (nor, of course, does this represent any formal endorsement of one type of bee feed over another). Still, it is interesting to contemplate how particular supplements affect not just bees but the hitchhiking microbes that have adapted to life in their guts.

One thing is clear from these diverse studies. While many of us focus on the microbes whose effects are damaging to bee colonies, most hive microbes are neutral or even beneficial to their bee hosts in Summer and Winter. Bees have been harnessing this power for millennia, and we would do well to help them sustain the right mix of gut partners.

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Found in Translation

City Bee, Country Bee
By: Jay Evans, USDA Beltsville Bee Lab

In Aesop’s fable, City (Town) Mouse, Country Mouse, a city mouse regales her skeptical country cousin with a rosy view of high density living. Sampling both, the country mouse prefers to stay put, largely because “the country mouse lives in a cozy nest at the bottom of a tree. Her home is small, but it is warm and comfortable.” Plus… no cats!

Beekeepers and bee scientists like to contrast the lives of bees under our care in apiaries (dense cities of colonies) versus those out on their own in trees. Aside from giving general insights into bee biology, these comparisons can predict the risks of managed and feral bees sharing disease while also showing how well ‘city’ and ‘country’ bees deal with various stresses. We have great data for the numbers of managed colonies, but how many country bees are we talking about?

I have discussed before the achingly beautiful (and hard) work by Tom Seeley and students assessing feral bees in a U.S. forest. Borrowing from those and similar studies, we can get a rough estimate of how many country bees there are in hollow trees and other cavities. My Sunday afternoon and small brain can’t grapple with honey bee density in deserts and the vast tundra, but considering four adjoining states (New York, Pennsylvania, Maryland and Virginia) with decent land-use data from the USDA (https://www.ers.usda.gov/data-products/major-land-uses/maps-and-state-rankings-of-major-land-uses/), we can estimate ‘suitable’ acreage (fallow fields, pasture and forests) at around 58 million acres total (60% of the available land). Using consensus estimates of 2.5 colonies/square-mile (one colony/square kilometer, 0.004 colonies/acre), one arrives at 233,000 feral honey bee colonies in these four states. According to USDA (https://www.nass.usda.gov/Surveys/Guide_to_NASS_Surveys/Bee_and_Honey/) ,there were 67,500 managed colonies in these states on January 1, 2021, surveying beekeepers with five or more hives. Even doubling this number to account for backyard beekeepers and those who evade surveillance, there are still fewer managed than feral colonies in these regions.

So, free-living bees are likely to be important for their own sake, and for the environment. What’s it like out there? Taking a disease angle, several studies have compared the relative disease loads of managed and feral colonies in the U.S. Amy Geffre and colleagues from San Diego sampled boxed and free-living colonies (three colonies each) seven times over the course of a year to measure virus levels for three common bee viruses (Preliminary analysis shows that feral and managed honey bees in Southern California have similar levels of viral pathogens. 2023. Journal of Apicultural Research, 62:3, 485-487, DOI:10.1080/00218839.2021.2001209). Both colony types were remarkably similar in virus levels, changing with the season but hardly differing from each other.

In Persistent effects of management history on honey bee colony virus abundances (2021. Journal of Invertebrate Pathology 179:107520, https://doi.org/10.1016/j.jip.2020.107520), Lewis Bartlett and colleagues found similar patterns between free-living and managed colonies but noted that the style of management might play a role. Namely, colonies maintained in a larger commercial apiary (hundreds of colonies) tended to have the highest levels of most viruses, with feral and low-intensity ‘backyard’ colonies being about the same. As in most field studies, there is abundant variation for viral disease within each category, so these results will need even more sampling to see how viruses and bees fare under different management styles. Nevertheless, they suggest that beekeepers adopting a ‘country bee’ approach by spacing out colonies to reduce urban interactions will be doing their bees a favor.

In the most ambitious study to date, Chauncy Hinshaw and colleagues surveyed 25 colonies each from feral and managed colonies in Pennsylvania (2021. The role of pathogen dynamics and immune gene expression in the survival of feral honey bees. Frontiers in Ecology and Evolution, 8, 594263. https://doi.org/10.1080/00218839.2021.2001209). They surveyed ample bee numbers per collection (75 worker bees), perhaps getting a better sense of average disease loads. Even better, they paired similar city and country colonies from a bunch of regions, which helps account for other factors that might change virus loads. In this study, managed colonies tended to have lower levels of mite-transmitted deformed wing virus, presumably reflecting mite treatments, and roughly similar levels of black queen cell virus and nosema. Perhaps reflecting pathogen exposure, feral colonies had higher levels of several immune response proteins as well. Given the higher number of sampled colonies, these researchers were also able to show how their measurements related to colony fates. As in prior studies, deformed wing virus, presumably alongside mite loads, was a good predictor of a bad colony outcome.

Colonies showing higher levels of two immune genes, once other factors were evened out, were more likely to survive the study period. Arguably, these proteins might be good predictors of genetic components that help bees survive in the face of disease.

More can be done to contrast the lives and successes of city and country bees. These comparisons can help improve bee management by those of us keeping bees in clusters of Langstroth high-rises. It is also fun to think of bees in the ancestral habits they have followed for thousands of years. Country bees almost certainly have more threats now than they did when humans were more scarce, and there has to be some level of contact between city bees and country bees that muddies all of these comparisons, but in many ways the presence of country bees at all is comforting. Left to their own care, they are making country homes work wherever they can, and that is a good lesson for beekeepers.

In full disclosure, the lives of country bees were not on my mind until a recent inquiry from British bee researcher Francis Ratnieks and his graduate student Ollie Visick. In their Laboratory for Apiculture and Social Insects (https://www.sussex.ac.uk/lasi/), they are comparing the lives of free-living honey bees in their native range to their hived cousins. As ecologists, their studies will give insights into how honey bees used to live in the forests and fields of England. I thank them for the prompt (and welcome hot tips from any of you) and look forward to reading their results!

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Found in Translation

Teaching Bees New Tricks

By: Jay Evans, USDA Beltsville Bee Lab

Bees have innate (think ‘robo-bee’) and learned (‘show me, sister’) behaviors. Recent work with bees has explored the boundaries of these two forms. While it is dangerous to put our own biases on animal behaviors, the complex behaviors measured seem to include ‘play’, ‘puzzling’ and ‘dancing’. Oh yeah, and they can count as well, even showing an awareness of ‘zero’ things, but that was yesteryear’s news from Scarlett Howard and colleagues (Numerical ordering of zero in honey bees, 2018, Science, DOI: 10.1126/science.aar4975).

What is fascinating about work coming out just this year is that not only do bees show complex behaviors, but they seem to get better at those behaviors by watching their nestmates. Bee dances will be familiar to most beekeepers and students of animal behavior. Successful foragers often tell their sisters where the good stuff is after finishing their foraging flights. Specifically, foragers signal both direction and distance to flower sources using the waggle dance. True to its name, and shown graphically to the right, this dance involves a bee streaking across the comb and shaking its abdomen for the edification of sister foragers. The angle of this dance on a vertical patch of comb signals the direction of a good food source relative to the current position of the sun relative to the hive. The length of each dance streak provides an estimate of the distance to flower patches (or to sugar baits planted by curious naturalists). By repeatedly dancing, they drum up interest and lead future foragers to a better understanding of how far they might have to fly to get these rewards. The discovery of this dance language is decades old, and justified a share of the Nobel Prize in Physiology or Medicine in 1973 for Austrian bee researcher Karl von Frisch. The recent work ups the game by showing that much of this behavior is learned by watching older, more precise, dancers.

Shihao Dong and colleagues set out to study Social signal learning of the waggle dance in honey bees (2023, Science, DOI:10.1126/science.ade1702). Specifically, they judged the dancing skills of self-starters relative to those of bees that were mentored by older, experienced, dancers. To produce a swarm of naïve dancers, they established colonies comprised solely of like-aged bees, so that all bees reached foraging age together and were therefore less likely to benefit from matching the skills of a senior dancer. Bees from these ‘Animal Farm’ colonies were compared to marked bees of the same age which had grown up gazing at the dances of experienced dancers in colonies with a typical age profile. Naïve bees consistently over-stated the distance they had flown to flowers, in effect telling nestmates to fly right past suitable food sources. They also showed more ‘Dance Disorder’ than both older bees and bees that had been exposed to older dancers. Dance accuracy for all dancers improved over time, it just improved much more quickly when bees had older mentors to watch. So what is the lesson here for beekeepers? No, you can’t force your teenager to watch you dance and expect them to get it, but you CAN see how bees in colonies with an abnormal age structure, thanks to rapid premature death of foragers, might continue to slide by spending unnecessary time looking for food. Long-lived bees are those free of chemical stress, raised with adequate protein nutrition, and arguably bees that have avoided mites and other disease. When you protect your bees from these stresses, just think of how their dance lives will improve.

In a study that, for me, deserved two SMH’s, bees were trained to take on puzzle behaviors, or behaviors that simply don’t present themselves to bees when scientists aren’t around. Working with bumble bees, Alice Bridges and colleagues first taught their bees to open small food boxes by pushing on colored (red or blue) tabs. This a behavior I am not sure I could teach my dog, but she is a bit slow. They then checked to see if bees could follow the lead of a nestmate who had already figured out the box trick. While self-learners emerged in the control colonies sometimes got the knack for opening boxes, bees who observed a nestmate open a box were more likely to successfully mimic that behavior. Over time, bees with a teacher opened more boxes, faster, and were rewarded with more sugar treats. Honey bees and some other bee species are known to spontaneously ‘rob’ flowers by chewing directly into nectar pools when those pools are too deep in the flower for their tongues to reach. It would be neat to see if such nectar robbing is also a learned trait, passed on by adventurous foragers who had to learn the trait the hard way. If so, can such teachers target their lessons to their nestmate sisters?

All of these studies push the known boundaries for bee awareness and behavior, showing all the more how lucky we are to have formed bonds with honey bees and other insects. Clever behavioral scientists will no doubt continue to discover profound, and maybe a bit unsettling, awareness by insects. This awareness is likely to be most evident in the highly social honey bees and bumble bees. What’s next, spelling bees? Stay tuned. In the meantime, get out, find a friend and improve your dancing.

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Found in Translation

Bees have an increasing say in soybeans

By: Jay Evans, USDA Beltsville Bee Lab

Farmers and scientists debate the extent to which one of our country’s favored crops, the soybean, benefits from honey bee visits. Nor are they sure that having bees visit soybean crops is a net positive for the bees. Despite research documenting strong benefits to soybeans from honey bee visits (dating since the youth of former Bee Culture editor Kim Flottum, https://www.beeculture.com/found-in-translation-19/), a perusal of thousands of studies related to soybean farming shows little emphasis on how and when bees should be deployed. As one metric, a March 2023, Google Scholar search of papers mentioning “soybean yield” and “honey bee” provided 276 references. The same search excluding the term “honey bee” provided 62,200 references. This overall trend has not improved in recent years; papers mentioning soybean yields that do not mention honey bees number 5,110 since 2022, while only 32 papers mention honey bees. Fortunately, those 32 papers provide some really important advances. The upshot is that bees can greatly improve soy production, while potentially gathering a resource for themselves and their keepers. What remains to work out:

1. How can beekeepers practice safe soy?
2. How can growers choose varieties and management practices that harness bee visits to boost production of a vital row crop?
3. How can the two sides meet up to work out deals that benefit both industries and the environment?

On the soy side, honey bee pollination impacts were described this month in a freely available paper from Decio Gazzoni and João Paz Barateiro (Gazzoni, D.L. & João Vitor Ganem Rillo Paz Barateiro. 2023. Soybean yield is increased through complementary pollination by honey bees, Journal of Apicultural Research, DOI:
10.1080/00218839.2022.2161219). These authors showed that, with the right conditions and soybean varieties, honey bees increased soybean yields in controlled environments by 8.5-18.2% in four trials across three years. This increase is not as dramatic as other studies from different cultivars, but still reflects a lot of beans. Hannah Levenson and colleagues at North Carolina State University also showed recently that supporting bees merely by expanding local non-crop habitat led to a significant difference in soybean seed (bean) weights. In an exhaustive survey of 7,000 bees in the field, they found that 30+ bee species had collected soybean pollen but honey bees tended to be more faithful than others for soy versus alternatives (Levenson, H. K., A. E. Sharp, and D. R. Tarpy. 2022. Evaluating the impact of increased pollinator habitat on bee visitation and yield metrics in soybean crops. Agriculture, Ecosystems & Environment 331:107901, https://www.sciencedirect.com/science/article/abs/pii/S0167880922000500).

If bees are generally good for soybeans, are these visits doing bees any good? Chia-Hua Lin and colleagues at The Ohio State University have been on that story for some time and recently published a complex study asking whether bees 1) make it to abundant local soybean fields and 2) bring home resources for their colonies (Lin, C.-H., Suresh, S., Matcham, E., Monagan, P., Curtis, H., Richardson, R. T., & Johnson, R. M. 2022. Soybean is a Common Nectar Source for Honey Bees (Hymenoptera: Apidae) in a Midwestern Agricultural Landscape. Journal of Economic Entomology, 115(6), 1846-1851. doi:10.1093/jee/toac140). In a citizen-science twist, the scientists asked members of the Ohio State Beekeepers Association to bring honey collected by bee colonies from across the state to their Fall meeting. This honey was screened for the presence of different pollen types under microscopy. As indicated by the title, soybean pollen was commonly found in Ohio honeys. More than half of the screened honeys held soybean pollen, and this increased for honey derived from foraging in July and August, when soybean flowers were most common. Finally, the authors used the waggle dance, the signal bees use within their colonies to direct nestmates to good foods, to show that returning bees are eager to tell their nestmates about soybean rewards. For medium-distance flights, returning bees were more likely to ‘dance’ that they had visited soybean fields than other fields, complementing the pollen collection data and saying that bees preferentially target soybean fields over the alternatives. Dr. Lin has backed up this work with some truly remarkable studies covering the attractiveness of dozens of soybean cultivars to bees in common gardens (e.g., https://ohiocroptest.cfaes.osu.edu/soy2022/2022_OSPT_pollinator_report.pdf) and is working relentlessly to improve cross-pollination between beekeepers and soybean growers.

Team B & B (Bees and Beans) collecting flowers in soybean plots last Summer. The white stakes are Karlan Forrester’s audio recorders. Photo provided by Chia-Hua Lin from the Rothenbuhler Honey Bee Lab at The Ohio State University

In ongoing work, graduate student Karlan Forrester (working with Chia-Hua Lin and Reed Johnson at Ohio State), has worked out innovative methods for tracking bees as they zero in on soybean flowers, while also confirming that certain soybean varieties are more rewarding, and hence attractive, to discerning bees (Forrester, K. C., Lin, C.-H., & Johnson, R. M. 2022. Measuring factors affecting honey bee attraction to soybeans using bioacoustics monitoring. BioRxiv, 2022.2011.2004.512777. doi:10.1101/2022.11.04.512777).

In looking for soy-bee stories that describe ways to enhance this partnership, I came across a series of fascinating works from the other side of the world. Dr. Dolapo Bola Adelabu, a researcher from the Free State of South Africa, and his colleague Angelinus Franke, found remarkable increases in soybean yields that can be attributed to visits by bees and other pollinators (Adelabu, D.B., Franke, A.C. 2023. Beneficial Role of Pollination and Soil Fertility for Soybean Production in Mountainous Farming Conditions. In: Membretti, A., Taylor, S.J., Delves, J.L. (eds) Sustainable Futures in Southern Africa’s Mountains. Sustainable Development Goals Series. Springer, Cham. https://doi.org/10.1007/978-3-031-15773-8_5). These yields were greater than 50% when combined with optimal fertilizer supplementation of crops (Nitrogen and Phosphorous), with less striking increases under poor soils. Farming in this region of southern Africa, in a rugged corner of the Free State, is distinguished by “smallholder” farms, where farms are interspersed with homes and natural areas. This farming scheme allows for both wild bee habitat (honey bees are not routinely kept in hives here) and presumably a range of alternate food sources for bees when soybeans are not in flower. In conversing with Dr. Adelabu, the studies did not distinguish Apis mellifera from other bee species, but it seems likely that honey bees were a major member of the pollinating community. Thanks to this research, the services bees provide in terms of local soybean yields, among other crops, justifies the work needed to keep healthy bee habitat. The two scientists in this work are also more broadly interested in schemes to provide healthy nutrition to a fairly dense human population, while maintaining a sustainable environment, ( e.g., https://www.ufs.ac.za/aru/aru-team/aru-team/prof-angelinus-franke). Hannah Levenson phrases it well in her article, “As such, pollinator habitat should be designed to provide resources across the entire active season to help these important pollinator populations, especially since many crops have short bloom durations.”

One hope from all this research for the U.S. will be improved dialogue between beekeepers and soybean farmers, ideally driven by profits on both sides. This dialogue will help bees collect soy flower resources while minimizing collateral damage from agricultural practices, including the need to treat for crop diseases and insect pests. In the meantime, what are the best practices for beekeepers around soybean farms? The Honey Bee Health Coalition has focused on this issue, leading to a draft of guidelines led by Adam Dolezal at the University of Illinois showing how management practices, from pesticide applications to habitat, can be more bee-friendly (https://honeybeehealthcoalition.org/resources/soybean-best-management-practices/). Making more food on fewer acres is good for the planet and the economy, and it is great that scientists and farmers on both sides are tackling the soy-bee system in a rigorous way.

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Found in Translation

Social Nature and the Hive Life

By: Jay Evans, USDA Beltsville Bee Lab

Picturing the Spring that will be upon the northern hemisphere when this essay is published, I feel a deep longing to see our bees in full growth, bringing back diverse pollen baskets and crops full of abundant nectar. Spring is my favorite season and it is almost painful to think of it as I write this in February (to many of us, the longest month). As a passionate beekeeping ally, I firmly believe that on the whole and in most settings honey bees are not only a tremendous asset to humans but intrinsically worthy in their own right. As messy as it might seem, this is true in both their introduced and native ranges (Eurasia and Africa for the ‘western’ honey bee).

Except for one 14 million-year old flattened specimen that fossil-hunters feel is in the genus Apis (all species of which have comb-forming, stinging, honey-storing social habits), there is no firm evidence that honey bees lived in North America before European colonists arrived a few centuries ago. Once here, however, honey bees flourished, swarming from their woven homes and making themselves an important part of both agricultural and natural habitats. In the midst of Winter, I feel the need to celebrate this flourishing.

That said, this is not another economic essay on the value of honey bee pollination or colony products, although $20-25 billion added to the U.S. economy in diverse, nutritious foods is not trivial. Nor is it another diatribe that bee-mediated pollination nourishes people throughout the world, nor that honey bees provide a cash crop for millions of families, with little startup costs, in communities that are stressed for both cash and nutritious foods.

And this is not a tribute to all the hardworking beekeepers, with from one to 80,000 colonies, who battle a variety of stresses to stay in the game (though I am not above pandering to that crowd).

It’s not even a worshipful look at how pollinators have shaped our world over 100+ million years, not simply by supporting billions of humans but in making every landscape just a bit more colorful and dynamic. This collaboration between bees and flowering plants, which started early and ended well for both, is wonderfully described by Sophie Cardinal and Bryan Danforth in their 2013 paper Bees diversified in the age of eudicots, Proceedings of the Royal Society B, https://doi.org/10.1098/rspb.2012.2686. I will tackle the larger economic and environmental benefits of honey bees and other pollinators in the future, this essay is more personal.

I would argue that we socially aware humans just need honey bees beyond their great services. To me, this need comes from two drivers. First, honey bees mirror our own inescapably social natures and teach valuable lessons therein. Second, if you try even half-heartedly to place yourself in the mindset of honey bees and other pollinators you can’t escape thinking about, and striving to improve, the plant resources and the overall environment they fly over and visit on their foraging flights.

First, the social connection. It is easy to revere a species in which selfless workers provide for relatives they most likely will never meet. There are so many facets of honey bee communication, biology and nature that are mirrors for our own, leading to profoundly interesting behaviors that resonate with the good and bad of our communities. My gateway to social insects and ultimately a life studying honey bees opened with a single lecture by an ant biologist, after which I went to my dorm and decided it was inconceivable to fritter my life away without studying these special creatures who build empires largely because they choose, 90% of the time, to drop their conflicts and work for a common goal. Ignoring their preferred diets, ants and honey bees are quite similar. Most importantly, both have succeeded in no small part because they divide tasks efficiently in colonies and can thereby both out-compete their solitary neighbors and regulate their home environments. Thomas Seeley’s book The Lives of Bees: The Untold Story of the Honey Bee in the Wild (2019) is a great entry into the wonder of bee inner worlds, while German professor Suzanne Foitzik shares similar life stories for ants in her 2021 book Empire of Ants: The Hidden Worlds and Extraordinary Lives of Earth’s Tiny Conquerors. In my case, the itch to learn about social insects became a full-on rash after opening a small student beehive for the first time while devouring the many stories of how honey bees and humans have been partners for thousands of years. From “busy as a bee” to “dance language” and “guard bees”, how we think of bee societies is hard to decouple from how we view our own. Not surprisingly then, neither bee nor human societies are perfect. Both show conflict within, vulnerabilities to parasites of all sorts and an occasional tendency to trample other beings, but both are marvels to behold, and exhilarating to compare and contrast.

A second preeminent reason to value honey bees is that they truly provide a gateway to understanding nature. When beekeepers see their bees exit the hive, circle-wave their home and sail off, they marvel at what that tiny bee will see on a journey across the landscape, wishing the bee luck and the memory cells to return after a successful foraging trip. This care for one’s bees inevitably leads to a greater appreciation for the flowering world, leading beekeepers to seek ways to improve and diversify the green world their bees encounter. Beekeepers fret over, and are noisy about, any ill winds that arise from degraded environments within two miles of the colonies they host. Habitat loss, climate, land practices and disease all impact the health of honey bee colonies, and beekeeping forces us to learn about each of those topics. Every beekeeper also has a keen sense of weather and the seasons. Okay, the same is true for gardeners, birders and hunters… and by some stretch of the imagination even golfers, although better if they let their ‘greens’ revert to wildflowers. Similarly, beekeepers are among the most knowledgeable humans with respect to how diseases spread, how to slow infections, and when it’s time to seek a doc, even if we neglect that knowledge sometimes with our own health and that of our colonies.

It’s not an easy path, and beekeepers often stumble. But, bees and beekeeping give back incredible riches to those who listen to the buzz and hitch a ride with their bee teachers. Hope springs eternal and here’s hoping your Spring is bountiful.

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Found in Translation

Bees Good

By: Jay Evans, USDA Beltsville Bee Lab

Waiting for Spring makes one hopeful and, simultaneously, a bit reflective on why we all keep at this, despite heavy Winter losses and expenses. This year, massive floods in California will wreak havoc with bees and beekeepers in holding yards and during the first commercial stop of the year in almond plantations. Most years the opposite is true; crippling droughts decrease yields from almonds and other crops, diminishing the agricultural benefits of bee pollination. Still, most of the time, bees and beekeepers get a break and honey bees and other pollinators provide a solid boost to the production of healthy foods. This essay is devoted to the bees and beekeepers whose actions improve food production and human welfare.

Our sister branch of USDA, the National Agricultural Statistics Service (NASS), provides quarterly and annual views showing how honey bees impact humanity in the USA (https://www.nass.usda.gov/Surveys/Guide_to_NASS_Surveys/Bee_and_Honey/index.php). These reports document how the hard work to keep bees alive pays off in the farming economy and the food supply. Jennifer Bond and colleagues at the USDA’s Economic Research Service pulled data from NASS and other sources to generate a full view of the bee industry and its drivers in Honey Bees on the Move: From Pollination to Honey Production and Back (2021, https://www.ers.usda.gov/webdocs/publications/101476/err-290.pdf). This short book shows the challenges faced by beekeepers and the targets that keep them on their toes, highlighting that 80% of annual pollination income to beekeepers is derived from one early-season source (almond plantations, flooded or otherwise). Bees and their migratory keepers then disperse widely for additional pollination events and, weather and habitat permitting, the production of honey and wax. Overall, beekeepers receive $320 million in pollination fees for their efforts, and these efforts have a twenty-fold greater impact on U.S. crop production.

Pollination of crops not only provides an economic engine for growers and (some) beekeepers, but pollination by bees is literally saving lives. A recent global analysis generated values for pollination impacts on world crops by estimating decreased productivity when bees were limiting (Matthew Smith and colleagues, Pollinator deficits, food consumption, and consequences for human health: A modeling study, 2022, Environmental Health Perspectives, 130(12) 127003-1 https://doi.org/10.1289/EHP10947). By looking at peaks versus observed productivity across farmed regions, the authors estimate that inadequate pollination decreases yields for fruit and nut crops by 5%, on average. Similarly, vegetable yields are reduced by 3%. These estimates cover 60+ crops that supplement the diets of billions of people on all continents except Antarctica. Using conservative measures, the authors estimate that 500,000 people die annually due to decreased food yield or quality caused by missed pollination events by bees. This human toll differs across countries, with some populations suffering from all-out hunger and malnutrition while others (including the United States) are impacted more by shifts in diet tendencies away from more nutritious pollinated crops such as fruits and nuts. In a second recent paper (Pollination deficits and contributions of pollinators in apple production: A global meta-analysis, 2022, Journal of Applied Ecology, DOI: 10.1111/1365-2664.14279), Aruhan Olhnuud and colleagues present data for one critical worldwide fruit (the apple) and argue for even greater impacts of missed pollination on yields and seed set, in the range of 40% and 20%, respectively, much higher in some countries. Seed set for apples does not limit the industry overall, but fertilized seeds lead to a more attractive fruit shape. Honey bees, of course, are not the only insect pollinators of crops and both of these papers take great pains to account for the impacts of diverse pollinators. Nevertheless, in many counties, including ours, honey bees are the primary pollinators of crops, especially for larger farms.

While these studies focused on pollination impacts, honey bees provide a bounty for beekeepers small and large that was not accounted for in these two studies. The nutritious value of honey, and to a lesser extent pollen and brood, improves nutrition in many countries. Further, the receipts from honey and wax sales have a huge impact on human health worldwide and are arguably one of the most important sources of small-farm income in developing and industrialized incomes. Bernard Phiri and colleagues analyze yields from hive products worldwide in Uptrend in global managed honey bee colonies and production based on a six‑decade viewpoint, 1961–2017, 2022, Scientific Reports 12:21298, https://doi.org/10.1038/s41598-022-25290-3). This fascinating synopsis highlights the losses and (mostly) gains of beekeeping across continents alongside the economic and population drivers behind those changes. As has been well documented, North America has seen a 30% decrease in honey bee colonies since 1961, while Europe (including Russia) has lost 12% of its colonies. South America, Africa, Australia and Asia have more than compensated for those losses, doubling or even quadrupling (Asia) managed hives in that time frame. Overall, the number of managed honey bee hives has doubled since 1961, matching a doubling in human population. All regions have perfected honey and wax harvesting, with honey yields even in North America surpassing those of prior years, despite lower colony numbers. This North American increase reflects heavier harvests in Mexico and Canada that outweigh decreased honey yields in the U.S. (https://www.visualcapitalist.com/cp/mapped-food-production-around-the-world/). Asian countries increased honey harvests by eight-fold over this time frame. It would be fascinating to estimate how greatly honey production impacts populations worldwide, not simply in local consumption but as an attainable and sustainable cash crop in developing and more industrialized countries. My guess is that the impacts of honey harvesting on lives improved and saved from premature death would rival that achieved by increased pollination from managed hives.

Whether you are keeping bees for family munchies, selling honey on a table or fully engaged in commercial pollination and the production of hive goods, you are playing a role in an essential partnership with one of the planet’s truly extraordinary animals. Thanks for doing that.

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Missing Their Better Half, More on Drone Genetics

By: Jay Evans, USDA Beltsville Bee Lab

Last month I wrote a tragic, and maybe a little droning, article about the shortcomings of male honey bees and their fragility. On a more uplifting note, drone genetics have great potential for use in honey bee breeding. Male bees, like male ants and male wasps, have half a deck of chromosomes, 16/32nds to use a precise carpenter term. These 16 chromosomes provide all of the information needed to make a bee (obviously) but with no redundancy for the most part. When there is a critical mutation in a critical gene, that bee will not fly. This liability is actually a gift in disguise for breeding and genetics in several ways.

Remember that, despite their limited job duties, not all male bees are equal. Differences among drones impact their ability to contribute genes during mating, and the value of those genes to their unseen offspring should drones win the mating lottery. Bradley Metz and David Tarpy showed that male bees in commercial beekeeping operations differed by two-fold in weight and by an amazing 100-fold in the amount of sperm they have available for mating (Metz, B. N., and D. R. Tarpy. 2021. Reproductive and morphological quality of commercial honey bee (Hymenoptera: Apidae) drones in the United States. Journal of Insect Science 21, https://doi.org/10.1093/jisesa/ieab048). By their estimate, 6.5% of adult drones in commercial operations were of ‘low quality’. To produce males matching the subpar guys, these scientists had to raise males in smaller worker cells. As expected, 83% of males raised in worker cells were graded as ‘low quality’, versus 2% of males raised at the same time in proper drone cells. Since males are unlikely to be raised in worker cells in the field, other colony or genetic factors must lead to the production of low-quality males. The usual suspects are disease, chemical stress and poor nutrition, although this study did not explore those causes. Interestingly, bee genetics can also play a role in variable drone traits, and in drone reproductive traits in particular. Garett Slater and colleagues reviewed substantial data showing that races of bees differed consistently in drone traits such as sperm count and sperm longevity (Slater, G.P.; Smith, N.M.A.; Harpur, B.A. 2021. Prospects in connecting genetic variation to variation in fertility in male bees. Genes, 12, 1251. https://doi.org/10.3390/genes12081251). While mated queens use only a fraction of the sperm received over the multiple mating events they engage in, there is some evidence that queen egg-laying is negatively impacted by mating with poor-quality males. Overall, these studies indicate the value of exposing your queens to healthy males.

Given all these weaknesses, what do males bring to the queen selection table? Being haploid means that individual males can have a disproportionate effect on offspring traits. In a hypothetical mating between a queen and a single male, the worker bee offspring are “super-sisters” in that they are identical on their dad’s side. In contrast, sisters share roughly half of their mom’s genotype (a term for the combined variants seen in a typical diploid animal). Male-driven breeding, coupled with instrumental insemination (since no one has time to direct males on the wing to precise matings), has huge potential to shift bee populations toward desirable traits. In our group, Laura Decanini led such an attempt for earlier efforts to identify resistance to American foulbrood (Decanini, L. I., A. M. Collins, and J. D. Evans. 2007. Variation and heritability in immune gene expression by diseased honey bees. Journal of Heredity 98:195-201, doi:10.1093/jhered/esm008) Starting with genetically homogeneous breeder queens, from a singly-mated Italian mom, we were able to produce a 100-fold range of immune traits when crossing those queens to a diverse set of 26 local drones. Heritability for both immune activity and survivorship in the face of P. larvae was high, as measured by comparing immune traits of resulting offspring with their ‘aunts’ from the 26 drone source colonies.

Even more powerful are attempts to screen drones themselves for desired traits, then collect and use sperm only from the drones who aced their fitness test. Ivelina Ivanova and Kaspar Bienefeld in Germany attempted to use drones as a surrogate for worker hygienic behavior, by subjecting drones to the ‘Proboscis Extension Reflex’ a common assay for learning and behavior in workers. (Ivanova, I. and Bienefeld, K. 2021. Suitability of drone olfactory sensitivity as a selection trait for Varroa-resistance in honey bees. Scientific Reports 11, https://www.nature.com/articles/s41598-021-97191-w). In worker bees, the PER can be used to assess responsiveness to the chemicals that trigger hygienic behaviors. Bees, which are smarter than most insects, will stick their tongues out for a food reward and can be trained to do so for cues like smells, learning like Pavlov’s dog to associate those smells with something good. Males in this study figured out the PER, as do worker bees, although males apparently do so with less vigor and more ‘nervousness’. Also, in the current study, “We observed a greater unwillingness of drones to respond to the CS+ and the sugar solution on cold or rainy days, although the temperature in the laboratory was regulated”, and “during our preliminary tests, we also observed high drone mortality if drones were treated according to existing bee protocols”. To go easy on these fragile males, the PER study was shortened, and the authors were able to generate usable data. Sadly, males that scored well in these standardized tests did not father the most hygienic offspring, so there was a disconnect there somehow. Still, males from high-scoring colonies helped perpetuate that trait, a validation of PER and comb-based hygienic tests for improving this key trait… but only when female bees are asked to take the test for their brothers. This does not rule out using male bees as a direct screen for individual resistance traits, including immunity. Drone-level screens of immunity followed by instrumental insemination give a direct path to stock improvement since drones fend off disease with the same immune response as their sisters. Scientists, including my USDA colleague Michael Simone-Finstrom and bee breeder Daniel Weaver, are using drone screens of disease response to enhance stock resistance (https://www.ars.usda.gov/research/project/?accnNo=441927). Drones still have time to show their strengths and it is fascinating to contemplate how being ‘haploid’ affects male contributions to colony life. Something to buzz about as we edge past the long drone of February toward Spring and colony renewal.

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Found in Translation

Save the Males

By: Jay Evans, USDA Beltsville Bee Lab

Male honey bees are not afforded much respect. If a male bee had the mojo to write a memoir it would be entitled “Eat, Mate, Die: One bee’s journey toward the audible pop”. No movie options there, despite the sadists just waiting for the dramatic ending. Nevertheless, these droning lives are critical for the generational success of honey bee colonies. Recent research has explored how male bees, fragile though they might be, contribute to colony health and the longevity of laying queens. There are also new insights into how biological and environmental threats impact males and thereby colony success.

First, male bees truly do have a smaller behavioral repertoire than females. Males are also sheltered from many of the stresses faced by worker bees and long-lived queens. The typical male bee, following a leisurely 24-day development time, emerges from his roomy honeycomb cell and simply ‘lives’ for more than a week before taking his first flight from the colony. No glands to produce wax, no glands to provide buttery food for developing bees, no grooming, no feeding of others, no defending the colony. During this time, the male’s energy is funneled into massive flight muscles and impressively large testes. When scientists look at male performance, they look at these two factors; can the boys fly and can they make viable sperm?

For the first question, it is important to determine if stressed males even live long enough to fly. Recent work by Alison McAfee and colleagues from the University of British Columbia and North Carolina State University showed that drones are more sensitive than worker bees to both cold temperatures and one pesticide (imidacloprid) under high lab exposure rates (Drone honey bees are disproportionately sensitive to abiotic stressors despite expressing high levels of stress response proteins. 2021. Communications biology 5,141, https://www.nature.com/articles/s42003-022-03092-7). Specifically, most drones simply can’t endure four hours at temperatures just above freezing, while their female counterparts survive fine. In this same study, drones died at two-fold higher rates than their sisters after exposure to 100 ppm imidacloprid. When exposed to a cocktail of field-expected pesticide doses, both drones and worker bees survived fine in these trials, but the evidence that drones were disproportionately sensitive overall prevailed.

Collecting semen from a drone honey bee that will be used to artificially inseminate a queen bee.

What about sperm? Much has been written about the impacts of drone sperm quality on colony health, using techniques mastered by retired USDA scientist Anita Collins (i.e., Collins, A.M. Relationship between semen quality and performance of instrumentally inseminated honey bee queens. 2000. Apidologie, 31, 421–429, https://www.apidologie.org/articles/apido/abs/2000/03/m0307/m0307.html). But what is it, outside of the lab, that leads to inviable drone sperm? Like most traits, both genes and the environment play a role. In a recent colony-level study, Lars Straub and colleagues measured the impacts of pesticide stress on “all the things drones are asked to do” (Negative effects of neonicotinoids on male honey bee survival, behaviour and physiology in the field. 2021. Journal of Applied Ecology, 58, 2515–2528. https://doi.org/10.1111/1365-2664.14000). Drones exposed to field-realistic chemical doses via pollen patties fed to their colonies died at twice the rate of controls. When they survived, exposed drones took longer than controls to take their first flight, drifted more often to the wrong colony and produced a higher ratio of defective sperm.

Does that defective sperm translate into poor colony health? Jeffery Pettis and co-authors showed that queens heading failing colonies in commercial beekeeping operations carry a higher proportion of damaged sperm (Pettis JS, Rice N, Joselow K, vanEngelsdorp D, Chaimanee V. Colony failure linked to low sperm viability in honey bee (Apis mellifera) queens and an exploration of potential causative factors. 2016. PLOS ONE 11(5): 0155833. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0147220). Sixty percent of the sperm stored by queens in failing colonies was dead, while only 30 percent was dead in healthy colonies. This need not reflect a history of dysfunctional dads in that poor sperm health might reflect the abilities of queens to keep sperm viable rather than damaged goods from the start. In fact, the researchers found higher levels of dead sperm after queens were subjected to temperature stress, passing the blame for sperm health to queens or (more likely) queen transport and management. While it is tough to measure the longterm effects of inadequate males on colony health, headway was made with data and a model generated by Bradley Metz and David Tarpy from North Carolina State University (Reproductive and morphological quality of commercial honey bee (Hymenoptera: Apidae) drones in the United States. 2021. Journal of Insect Science, 21: 2, https://doi.org/10.1093/jisesa/ieab048). Observationally, colonies produce a range of smaller and larger drones, with six to 10% of drones being below a threshold size mimicking that seen when drones are raised mistakenly in worker cells. These smaller drones differed in their abilities to pass on adequate sperm in both quantity and quality (sperm viability), and the authors use that fact to argue that less fit males can have a strong impact on queen longevity and the health of managed bee colonies.

Weirdness in male bee genetics play some role in their fragility. Male bees, like male ants and wasps, and males found in a handful of less prosperous insect groups, are generally ‘haploid’ from birth to death. They are born of unfertilized eggs that simply start dividing into tissues and eventually organs, forming a viable insect that has no genetic father. Being haploid comes with its own set of challenges. Most life forms outside of the bacteria and ‘archaea’ have a genetic father and mother. This means we have two copies of genes that encode most of the proteins in our bodies. This redundancy can be good as organisms develop, behave and prosper. For example, many survivable genetic diseases in humans and other organisms are survivable simply because one of two viable proteins in such cases can suffice for a critical life task. As scientists have noted, honey bee drones are thus uniquely vulnerable to dysfunctional proteins encoded by their exposed genomes. The work previously mentioned, by Dr. McAfee and colleagues, for example, contrasted males and their sisters specifically to see if males were the weaker sex because they are haploid or because of other biological differences. Their study suggests the latter. Nevertheless, there are surely impacts from having half a set of chromosomes in terms of breeding and bee evolution. Garett Slater and colleagues, in Haploid and sexual selection shape the rate of evolution of genes across the honey bee (Apis mellifera L.) genome (2022. Genome Biology and Evolution. 14(6) https://doi.org/10.1093/gbe/evac063) showed that genes that were especially active in male bees were evolving differently than genes equally active in both sexes, although it is not clear that this reflects playing with half a deck. The genetic impacts of being haploid, and the potential for this phenomenon to be exploited in bee breeding, are good topics for next month. Thanks to a handful of female and male scientists who have looked past the limited behavioral range of male bees, we now have critical information on the colony and environmental factors that conspire against drones, and the impacts of drone health on colony offspring borne from their brief and dramatic lives.

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The Big Sleep

By: Jay Evans, USDA Beltsville Bee Lab

In most of the northern hemisphere, beekeepers have put their colonies to bed for the Winter and are eagerly anticipating their Spring awakening. Unfortunately, only two-thirds of colonies that go into Winter come out alive, leading to silent Springs for large and small beekeepers and impacting early pollination events. The only upside, for some, is a booming market for package bees and nucleus colonies. The causes of Winter losses are many, and determining which threats are most important is an active research topic.

This research takes three forms: 1) Direct experimental tests of potential killers, 2) Correlative studies of possible causes within and outside colonies and 3) for the extremely patient, long-term studies of Winter losses at the apiary or neighborhood level across different habitats. The ultimate goal of this research, and of beekeeper observations of their own losses, is to manage bees and their environment in healthier ways. A short-term goal, if less satisfying, is to simply have a better grasp of how many colonies will be on hand before making commitments to pollinate or placing early orders for new Spring bees.

Experimental manipulations of colonies followed by a wait-and-see for Spring are challenging and expensive. To date, these experiments have pointed towards Varroa mite treatment as the single most important, and largely doable, management step needed to improve Winter survival, with nutrition, queen health and pesticide exposure all playing roles. These small-scale experiments are mirrored by insights from the Bee Informed Partnership’s Colony Management survey (www.beeinformed.org). Beekeepers remain the single most valuable player in maintaining colony health.

What about neighborhood or landscape causes for Winter losses? With increased tools for hive-monitoring tools and vital governmental resources for mapping reported land uses (e.g., the USDA’s Cropscape program, https://nassgeodata.gmu.edu/CropScape/), predicting landscape forces that sustain or kill bee colonies has become highly useful. I have highlighted the ‘Beescape’ project before (www.beescape.org), an effort to show beekeepers what is within foraging distance of their colonies. With parallels in other parts of the world, Beescape can guide apiary placement and nutrition management, and is also simply fascinating in a ‘Zillow’ sort of way in showing the best neighborhoods for raising bees. Land-use maps have been used to assess landscape features that favor bee health in habitats ranging from the western bee ‘breadbaskets’ to Philadelphia. As an example of the former, Dan Dixon at the University of North Dakota and colleagues from the U.S. Geological Survey mapped land use changes surrounding known apiaries across eastern North Dakota in Land conversion and pesticide use degrade forage areas for honey bees in America’s beekeeping epicenter (2021; PLoS One; https://doi.org/10.1371/journal.pone.0251043). They used this information to develop a ‘Quality Index’ for apiary sites, noting where colonies were likely to be exposed to insecticides and other threats and where they would be less vulnerable to those threats. As expected, areas with more natural forage, including those managed through the USDA’s Conservation Reserve Program, presented healthier forage options within reach of resident beehives. This recent work mirrors prior work in the same region, showing the importance of healthy forage for honey bee survival and honey production (i.e., recent work led by Autumn Smart from the University of Nebraska with the USGS team, Landscape characterization of floral resources for pollinators in the Prairie Pothole Region of the United States, 2021, Biodiversity and Conservation 30:1991-2015, https://digitalcommons.unl.edu/entomologyfacpub/949).

Given the decent insights from experiments and landscape-level surveys, why would anyone wait on decades-long surveys to identify the causes of colony losses? First, these surveys are the best for showing changes in forage and climate over the long term. They also help separate threats beekeepers and bees can address from those they cannot. A brand-new 10-year survey from Germany points out some known risks while also finding a surprising twist. Jes Johannesen and colleagues, in Annual fluctuations in Winter colony losses of Apis mellifera L. are predicted by honey flow dynamics of the preceding year (2022, Insects 13, 829, https://doi.org/10.3390/insects13090829), merge hive monitoring and weather data with actual colony losses (as reported in surveys) to explore connections across years.

First, the authors make the case that management practices and bees are fairly homogenous, and hence variation in colony losses likely reflects climate or other environmental external variables. This is perhaps more true in Germany than in the U.S. Counter-intuitively, years in which bees started to return with forage sooner, i.e., ‘early Springs’, were linked with both larger colonies and heavier Winter losses the following Winter. This result likely reflects longer growing seasons for varroa mites and the delayed impacts of those mites. When ‘start date’ is factored out, colonies that gained weight the fastest in a three-month Spring flow had higher odds of surviving Winter, so colony growth itself remains a good predictor of colony futures. In a sign that local conditions are critical, colony losses in August correlated with losses the following Winter in the same apiaries. It would be nice to see disease data for these colonies; perhaps they had high virus, nosema or other loads that might have been a predictor of bad news by the following Spring, if not a trigger for disease control that Fall. The most surprising result involved year-to-year changes. Apiaries with low losses one year tended to have higher losses the next, and vice versa. Their best guess for a cause of this odd trend was that prior or alternate years might act as a purge for locally bad colonies, and the survivors would be, at least momentarily, over-achievers. Again, these surveys did not involve actual sampling, so it is hard to test that idea. I hope your own colonies fare well this Winter and are buzzing when you check them in 2023.

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Climate Control

By: Jay Evans, USDA Beltsville Bee Lab

Honey bees control the temperature in the core of their colonies to a degree you can only dream of for your home. By humming muscles (burning sugary carbs) and ventilating, they stabilize both temperature and humidity across a wide range of outside conditions. How they do this and the causes of major shifts from normal hive conditions are topics of great interest for colony health. Running too hot in the Winter can stress the cells of bees, or at least reflect the wasteful use of honey. Running too cold also stresses bees, especially brood, and can put colonies at greater risk from parasites and pathogens (which tend to come from lineages that exploit less hot-blooded insects).

Beekeepers and scientists have developed and adopted numerous technologies for monitoring hive conditions. Superfans can find hours of videos by experts in this realm from the most recent International Bee and Hive Monitoring Conference, held at the University of Montana (https://www.youtube.com/playlist?list=PLK1L4YyuyoO1WxuH1Dg4sxhM-FOEDYhW_). Highly accurate thermocouples are inexpensive and depend on minimal energy. Similarly, monitors for humidity are readily available, as are monitors for sound. Slightly more complex probes can determine relative levels of oxygen or CO2 in the hive environment. All of these measurements can be reported out to the wider world via antennae aimed at cell phone towers or satellites, joining the cacophony of the ‘Internet of Things’.

Scientists using this technology receive unprecedented insights into how colony conditions, management and hive materials impact the bubble in which colonies live. In total, the results have some bearing on management and diagnoses of when things are going poorly. They also might change how you manage, feed and house your bees. The concept of indoor weather reports from beehives is not new, of course. Hive temperature values gathered by James Simpson for his 1961 paper Nest Climate Regulation in Honey Bee Colonies (https://www.science.org/doi/10.1126/science.133.3461.1327) are still accepted as truth for colonies in Winter and Summer and within and outside the cluster of bees. Namely, the cluster itself is HOT, and stable, fluctuating only slightly from 34oC (93oF). This cluster temperature trends lower and becomes a bit less stable in the absence of brood, but Winter bees from Texas to Toronto keep things amazingly hot and stable through the coldest Winter.

So how do beekeepers help their colonies control temperatures efficiently? I have written before about the resurgence in storing colonies in buffered buildings, or underground, during Winter as a means of decreasing stress and honey consumption. What about hive-centered fixes? Working from the outside in, what is it about the hive environment that helps honey bees regulate their inner selves? For any given climate, bees and beekeepers have some say about the building materials and integrity of colony homes. Some beekeepers feel that natural hive cavities and managed hive bodies that most closely match the ancestral homes of honey bees will lead to healthier bees. Groups such as Apis arborea (https://www.apisarborea.org) are leaning into this idea with naturalistic beekeeping. Others have focused on mass-produced and marketed options. My USDA colleagues Mohamed Alburaki and Miguel Corona have compared the well-used wooden Langstroth hive body to one of the available synthetic hive options. Using bee-free boxes and cold stretches of the Maryland Winter, they showed that synthetic boxes absorbed and maintained solar energy more effectively and (counter-intuitively to me) also kept the hive environment at lower humidity at a range of temperatures (Polyurethane honey bee hives provide better Winter insulation than wooden hives, 2022, open-access in Journal of Apicultural Research, https://doi.org/10.1080/00218839.2021.1999578). These are both desirable traits for a hive structure. Similarly, Daniel Cook and colleagues from Brisbane, Australia, showed in Thermal impacts of apicultural practice and products on the honey bee colony (2021, Journal of Economic Entomology, doi: 10.1093/jee/toab023) that polystyrene hives maintained heat far better than wooden hives, while also showing that stored honey, while costly to heat initially, acted as wonderful insulation for bees trying to keep warm. In prior work, Yasar Erdogran from Turkey did a similar study but with bee-filled colonies (Comparison of colony performances of honey bee (Apis mellifera L.) housed in hives made of different materials, 2019, in the obscure but accessible Italian Journal of Science, https://doi.org/10.1080/1828051X.2019.1604088). Here, polyurethane colonies had higher brood production and honey yields than wooden hives, but wooden hives with an exterior sandwich of insulation were significantly better than both, even during the Summer.

Other studies suggest that bees themselves, and their behaviors, are predominant in maintaining a cozy home. Using longterm and precise reporting of temperature and levels of CO2, William Meikle and colleagues showed how bees can make different houses work for them in Honey bee colonies maintain CO2 and temperature regimes in spite of change in hive ventilation characteristics, 2022, Apidologie, https://doi.org/ 10.1007/s13592-022-00954-1). Bees showed a narrow core temperature band in both standard hives and hives with a screen bottom board, and strong daily cycles in CO2. Colonies had higher CO2 levels when housed with screen bottom boards but this difference was not as large as the natural daily cycling of CO2. Dashing a good story, colonies did not show any sort of group-level ‘breathing,’ whereby gas levels changed on a cycle from seconds to hours. Building on the complexity and seasonal nature of all this, Ugoline Godeau and French colleagues monitored the temperatures of different parts of dozens of hives for two years (!), giving the best view yet of energy loss and heat production within bee homes. In their 2022 pre-print study Stability in numbers: a positive link between honey bee colony size and thermoregulatory efficiency around the brood (https://ecoevorxiv.org/9mwye/) they reinforce how remarkably stable hive temperatures remain, while showing minor changes with colony size, namely that worker bee population, and not brood numbers, per se, is positively tied to temperature stability. This is only true when brood is present and when probes are in areas containing brood. When brood is absent, as observed 60 years ago by Simpson, hive temperatures fluctuate madly.

So how can this information be used to improve beekeeping? It is evident that hive sensors can help determine optimal bee houses for any given climate, and perhaps these sensors will help beekeepers decide when and how to remove honey and swap out drawn frames for foundation with the least impact on the bubble their bees prefer. It is possible that multiple hive temperature sensors can tell beekeepers when brood is absent or retracting, but bees seem to be quite good at showing heat when even small patches of brood are present. Hive sensors that measure CO2 and other hive gases (oxygen, nitrogen, etc.) are more costly but give unique insights into bee activity, and perhaps the efficient use by bees of incoming energy. How these physical measures mesh with continuous monitoring of hive weight, and sound for that matter, remains to be seen. For now, for most of us, we can get general insights from studies that use accurate and constant probes, but our most useful insights (and satisfaction) will come from lifting hive covers.