Research at the Center for Integrative Bee Research (CIBER) at the University of California Riverside focuses on unique genes in the honey bee genome of Southern California’s survivor bees. These bees have adapted to thrive in challenging environments without human intervention, demonstrating resilience to diseases, climate extremes, and urbanised or intensively farmed landscapes. In this second article in our series, geneticist Christopher Allen uncovers the mechanisms behind their resilience. These discoveries will not only help identify bee genes responsible for these survival traits, but also pave the way for breeding stress-resilient bees which can provide essential pollination services in the future.

Decoding the bee genome

To unravel the secrets of survivor bees, we first need to understand their origins and genetic makeup. Inspired by consumer-based genome analysis companies like Ancestry and Embark, where many people easily provide saliva samples to glimpse their genetic information, researchers at CIBER are applying similar approaches to honey bees.

Historical records have documented the importation of several honey bee lineages from the ancestral range (Europe, the Middle East and Africa) into the USA. We now know that these ancestral lineages have been interbreeding and mixing up genetics across the country, creating populations that are distinct from their ancestors. Southern California’s survivor bees are a product of this mixing, and their genomes reflect the evolutionary forces of natural selection driving their fitness in challenging environments.

Tools of the trade: sequencing technologies

Now, how do we measure something so intangibly small and complex as DNA sequences? If you want to measure height, you could grab a tape measure and start recording. But DNA sequences aren’t visible, and they’re made up of millions to billions of tiny ‘letters’ (A, T, C and G) that are referred to as the genetic code. To read DNA, we rely on sequencing machines, which can capture these letters in a variety of ingenious ways at mind boggling fast speeds.

For example, Oxford Nanopore’s sequencers measure tiny changes in electrical currents as each individual DNA nucleotide that passes through a small hole in the machine. It’s like reading a squiggle of electrical signals that can be converted into the DNA sequence and it’s reading those squiggles at a dizzying rate of 400 bases per second.

Another sequencing technology we use relies on flashes of colour. Here, fluorescent tags are attached to each DNA base, and, as the machine reads the sequence, each base gives off a specific colour that the machine then reads as an individual DNA nucleotide. Imagine watching fireworks where each colour represents a letter in the genetic code. These approaches allow scientists to ‘read’ the invisible, revealing DNA’s secrets one base at a time, and driving discoveries in fields from medicine to agriculture.

Unlike traditional genetic studies that analyse small fragments or focus on one or a few genes, whole genome sequencing (using platforms such as ONT or Illumina) enables us to decode the entire honey bee genome. This approach provides a much more comprehensive view of the genetic information, allowing us to explore the full scope of genetic diversity. By examining complete genomes, we can uncover critical insights into the genetic basis of traits that make survivor bees unique and better understand how these traits are distributed across populations.

Utilising reference genomes

How do geneticists make meaningful comparisons from DNA samples? It all starts with a reference genome – a detailed map of an organism’s genetic blueprint. For honey bees (Apis mellifera), the first reference genome was published in 2006. Thanks to advances in sequencing technology, this was updated in 2019, providing a more comprehensive ’gold standard’ that serves as the foundation for assembling and analysing individual genomes. Every sample we analyse is constructed with this reference genome as a guide, ensuring consistency and comparability across datasets. This essential step allows scientists to accurately identify genetic variations and draw meaningful conclusions about evolutionary history, genetic diversity and ancestry.

A wealth of genetic data is available through the National Center for Biotechnology Information (NCBI), an online repository where scientists share and access billions of genetic records. For our research, we harness this resource to study Apis mellifera samples collected globally, using them to build an ancestral panel. It’s important to note that the ancestral panel is not a reference genome, but rather a collection of deeply sequenced genomes from individuals across Europe, Africa and the Middle East at 60-times coverage for high accuracy. This means that the machine that sequenced the honey bees’ DNA repeated the tests 60 times to increase accuracy, because even these highly sophisticated systems can make errors. These sequences, aligned to the reference genome, allow us to model ancestral genetic variation and trace the genetic makeup of Southern California’s survivor bees.

What can the genetic secrets of survivor bees tell us?

Understanding genetic diversity in bees isn’t just a scientific exercise; it holds real implications for the future of beekeeping and agriculture. By uncovering how different populations of bees have adapted over generations, we gain insights into their resilience against challenges like climate change, disease and habitat loss.

With the creation of a population-specific reference genome for Southern California, we could better understand how the environment is shaping genomes across microclimates. If we determine, for example, that coastal areas, mountain ranges and deserts all have locally adapted stock, this knowledge can guide breeding programmes to select for hardy, adaptable bees that thrive in a variety of environments. This could have wider repercussions for commercial beekeepers who may wish to provide premium pollination services or breed a specialised commercial stock for certain regions.

Ultimately, by decoding the invisible layers of bee diversity, we’re laying the groundwork for healthier hives and more sustainable beekeeping practices that can support food security and biodiversity worldwide.

In 2021 beekeepers in Trégastel, a town on the north coast of France that has a high population of yellow-legged Asian hornets (Vespa velutina), embarked on a four-year study into the impact of spring trapping of foundress hornet queens. Spring trapping has been controversial in France, so they wanted to find out whether the loss of early season insects as bycatch is a price worth paying for potentially fewer primary and secondary yellow-legged hornet nests later in the year.¹

The Trégastel invasion

After the first yellow-legged Asian hornet was seen in south-west France in 2004, its population spread across the country while a national strategy to fight this invasive predator was formulated. In Brittany, the invasion was noticed in the spring of 2010 and soon intensified, particularly in coastal regions. By 2019 studies showed a nest density of five nests per km2. Recently, in September 2024, a 77-year-old hiker died in Côtes-d’Armor after a yellow-legged hornet attack.

Trégastel, a town in Côtes-d’Armor (Brittany), has a population of 2,500 in a 7km2 area. In 2021, 63 nests were removed (a density of 9 nests/km2). In 2022, the hornet invasion began impacting the lives of all residents for the first time, as 90 primary and secondary nests (a density
of 12.9 nests/km2) were removed.

In July 2022, most of the apiaries in Côtes-d’Armor were invaded by the hornet. Five or six hornets would wait by hive entrances from sunrise to sunset and the stress of predation inhibited honey bee queens from laying eggs. The national hive mortality survey in France (ENHMA) showed that 30% of colonies were lost in the winter of 2022–3 in Côtes-d’Armor, 18% of which was attributed to yellow-legged hornet attacks.²

A high density of yellow-legged hornets disrupts even human community life, invading meat and fish stalls in markets, restaurant bins and endangering city gardeners trimming hedges and disturbing nests. Neither residents nor tourists are safe.

In August 2022, a serious attack on the public at a busy beach car park caused an evacuation and road closure. This prompted the Trégastel town council to follow the spring trapping recommendations proposed by GDSA22, a beekeeping health protection group in Côtes-d’Armor. Since 2020, this group has led a targeted campaign against the hornets based on spring trapping foundresses and analysing nest numbers.

The study begins

Although spring trapping foundresses has been very controversial in France for almost 20 years because of potential bycatch¹ GDSA22 members (volunteers and civil servants, including police officers and gardeners) worked together to deploy spring traps in Trégastel for eight-week periods each year.

The first task involved raising awareness of the Vespa velutina threat by creating a precise map of nests removed from municipal properties in each month in 2021 and 2022. This information was shared online and at regular public meetings.

At the first meeting, which was attended by approximately 110 people (out of 1,372 households), discussions revolved around the yellow-legged hornet’s lifecycle and the goal of environmentally responsible spring trapping of foundresses. The organisers explained that trapping and nest destruction was to be centralised by the town police with a dedicated telephone number, and financially supported by the municipality. Based on nest data from previous years, 53 volunteer trappers (2023) and 66 volunteer trappers (2024) were selected to give optimal coverage.

Traps were to be positioned close to flowers (camellia, apple trees) blooming in March/April. For budgetary reasons, only one type of affordable commercial trap plus bait was provided free of charge to each trapper for the whole campaign. Some traps were improved with floating twigs and 6mm holes made below the rim, to enable small insects to escape.

A trapper’s commitment form with a catch-counting sheet and four bait refills were distributed along with instructions on how to distinguish the yellow-legged hornet from other types of insects. A QR code label linked to information about the trapping campaign and information on insect identification.

How did spring trapping work?

The campaign was deliberately limited to seven to eight weeks. To minimise bycatch, trapping began across the region when the first foundresses were caught in six satellite traps and ended when the first workers were found in the traps.

The recommendations for trapping were:

• place the bait inside the trap and renew it every two weeks, noting the catches (number and species)
• place the trap in a sunny spot, a shrub near flowers (camellia shrub, if possible) and sheltered from the wind
• follow the instructions to start and end trapping, and return the trap with its catch-collection sheet to the police.

Perhaps because of weather conditions, the emergence of the first foundresses in 2023 and 2024 differed – the trapping campaign began in 2023 on 14 March and in 2024 on 2 April.

In Trégastel, the alert and removal of nests has been centralised since 2022. Nest locations are reported via a dedicated telephone number and the municipal police organise nest removals by a single company within 24–48 hours. All costs are covered by the town council – a service which is not common in France, so generally property owners elsewhere are reluctant to report nests for financial reasons.

Spring trapping results

Despite the traps being distributed as evenly as possible, the most impacted areas were residential and suburban where the largest numbers of nests had previously been discovered in 2021 and 2022 (areas 2, 7 and 8). In contrast, in agricultural and industrial areas, comparatively fewer foundresses were captured (area 4 and west of area 1).

In 2023, 1,146 foundresses were captured between mid-March and mid-May.

In 2024, the trapping campaign was delayed by poor weather, and only 598 foundresses were captured, despite more volunteer trappers.

The average number of foundresses found in each trap was 21.6 in 2023, but only 9.1 in 2024. In 2023, 18 trappers caught more than 25 queens, but in 2024 only six trappers captured more than 25 queens.

The bycatch

After being trained in species recognition, the volunteer trappers were asked to count non-target insects (bycatch) including Hymenoptera, Diptera and Lepidoptera. Perhaps because of the late start of the 2024 trapping campaign, there was more bycatch in 2024 than in 2023.

If available and financially viable, a totally selective trap would have been preferable as early season insects are essential for the preservation of biodiversity and for pollination services. The total estimated weight of bycatch for the entire campaign was 200–300g per year.

According to a 2021 paper, a single secondary yellow-legged hornet nest can collect 11.32kg of insect biomass (159 species), including 38% bees, 30% flies and 19.7% wasps.3 If we compare the 300g of bycatch per year with the knowledge that the hornets captured around 900kg biomass in 2022 (based on the 81 large secondary nests destroyed in Trégastel), then the impact of spring trapping is put in perspective.

The impact of spring trapping on the European hornet

In 2024, the 15-day delay to the start of the campaign regrettably meant that more European hornets (Vespa crabro) were caught than in 2023. Since European hornets emerge later in spring than yellow-legged hornets, it is likely that the poor weather in 2024 caused a greater overlap in their emergence.(4)

Despite this excessive trapping of European hornet foundresses, a large number of European hornet nests were recorded that summer. Some studies suggest that the simultaneous emergence of yellow-legged and European hornet foundresses might have increased nesting site competition between the species resulting in greater difficulty for the yellow-legged hornet to found nests because of the greater number of European hornet nests in the area in 2024. (5,6)

Nest removal results

The alert system and the commitment of residents made it possible to centralise and map the exact locations of nests. It is a difficult task, and some nests may have gone unnoticed in marshy areas or unfrequented land.

In 2022, with no spring trapping, 90 nests (nine primary and 81 secondary nests) were removed by the municipality.

Following the spring trapping campaigns of 2023 and 2024, the number of active secondary nests was reduced. In 2022, 81 secondary nests were found; in 2023, 38 secondary nests; and in 2024, only 29.

It is very tempting to link spring trapping to reduced nest building, but the decrease in secondary nests could be due to other factors. For example, a cold winter and Storm Ciaran in November 2023 might have impacted the number of surviving foundresses.

Primary nest finds

The campaign has raised the awareness of the general public, and more primary nests (+67%) were reported in 2023 than in 2022. In 2022 the first primary nests were discovered on 15 April, but in 2023 the date was three weeks later, on 10 June. In 2024, only two primary nests were discovered.

Secondary nests finds

Location

The 2024 secondary nests were located in similar areas to previous years: along wetlands (east of area 2 and area 8) and in areas for second homes where trapping has been weaker such as area 3 and along the coast (north of area 5 and area 2).

High levels of foundress capture (more than 25 per trap) frequently coincided with nearby primary or secondary nests spotted later in summer, enabling more focused trapping the following spring.

Delay in appearance

As with primary nests, the appearance of the first secondary nests was one month later in 2023 and 2024 than in 2022. The resulting later appearance of yellow-legged hornet workers significantly reduced the pressure on apiaries and hornet sightings drastically reduced that summer.

Size

From August 2023, we discovered almost exclusively ‘presumed secondary’ nests, the size of a basketball, at ground level in ferns, tree stumps, rabbit holes, small hedges and even concrete blocks on the ground. A few small primary nests, the size of tennis balls, were also discovered in late August.

Most nests found in 2024 were smaller than a basketball. Only three discovered in autumn 2024 had a diameter greater than 50cm. The building of secondary nests is linked to a colony needing more space and protection from predators. Did the late building of primary nests, a consequence of intensive queen trapping, disrupt the proliferation of yellow-legged hornet workers in early summer, and thus their decisions to build secondary nests? Could it explain the building of small secondary nests at the primary location and not higher in the trees?

How successful was spring trapping?

Spring trapping of foundress queens totalled 1,146 in 2023 and 598 in 2024. The collateral trapping of other insects remained low in both years (less than 300g), far below the expected potential predation by the yellow-legged hornets over the same period of time.

After spring trapping, the number of secondary active nests decreased by 53% in 2023, and by 24% in 2024, reaching an overall decline in nest finds of 64% compared to 2022. The nests were found to be much smaller and closer to the ground after spring trapping campaigns.

In this seaside town, several successive spring trapping campaigns may have reduced the spread of the yellow-legged hornet to a more acceptable level for the population and beekeepers. Educating people, organising communal efforts freely supported by public services have improved the efficacy of the campaigns.

Constant vigilance in 2023 and 2024 has led to no reported yellow-legged hornet incidents in the municipality in the past two years. Involving the community by updating residents on the spring trapping progress via a monthly newsletter proved useful. Most importantly, the financial investment of the town services (traps and free removal of nests) proved cost-saving: 64% fewer nests were eliminated in the past two years and there was improved safety for both human and insect populations.

Regionally, as part of the GDSA22 campaign against the yellow-legged hornet, several surrounding villages have also begun spring trapping campaigns. Trébeurden, 8km away, recorded a similar drop in predation. Compared to the rest of Brittany, where nest numbers are still on the rise, nest numbers in the Côtes-d’Armor showed a significant drop in 2023 (from 8,000 to 6,000 nest removals).

Moving forward, it will be vital to improve the selectivity of spring traps at an affordable price, and to combine better detection systems with environmentally friendly nest destruction methods. We also hope that a practical national plan will be implemented to contain the invasion of yellow-legged hornets.

With thanks to Sylvain Allet and Gaetan Brisseault (Trégastel municipal police officers), Sophie Piat (communication employee) and Christine Grell (town councillor of Trégastel town hall) and the 66 volunteer trappers.

Rémi Brouard is a board member of the French Société Centrale d’Apiculture (Central Beekeeping Association) (SCA) and the local Asian hornet team leader for GDSA22, a beekeeping health protection group for the region of Côtes-d’Armor in northern Brittany.

Christian Guespin is GDSA22 vice-president.

Marie Laure Legroux is SCA vice-president.

It’s never too early to think about swarming. By April, there should be lots of new bees coming through. The strongest colonies will be heaving with bees and the swarming instinct will begin to kick in once the colony starts to become crowded.

April may seem early to start swarm checks, but depending on the winter conditions and the strength of the colony, swarm preparations may already be under way. Swarm checks are usually performed every ten days or so. It is important for every beekeeper to recognise the difference between play cups, swarm cells, supersedure and emergency queen cells, and to act accordingly.

Pre-emptive swarm control

Last year, I split five colonies in late April. I wanted to increase the number of colonies in the apiary, so I had new boxes ready for the bees to be transferred into. Splitting a colony before swarm cells appear is sometimes called pre-emptive swarm control, in that the resulting split reduces congestion in the colony and it should reduce the urge to swarm. For this to work, you must have at least six frames of brood with a good mix of brood stages. From the six colonies I split, one of them never really got going, so I reunited it with the other colony late in the season by placing a piece of newspaper between the brood boxes to prevent the bees from taking exception to one another. This reuniting of the boxes helped to ensure the colony had a strong population and didn’t perish over the winter.

Money in the bank

¹Spring is the ideal time to make a few drawn frames, when the factors for wax production are present – warm weather, an abundance of young bees and a good nectar flow; bees won’t draw out wax from stored honey. Creating wax comb is costly in energy terms for the bees, so drawn-out frames are like money in the bank for future use. In Lesley Goodman’s book Form and Function in the Honey Bee, she states that it takes 1kg of honey to produce 60g of wax. Therefore, an average hive containing 1.2kg of wax has used approximately 7kg worth of honey to make it.¹

Drawn frames can be useful when splitting colonies or for comb replacement; combs should be replaced every two to three years as, over time, they accumulate traces of propolis, cocoons and faecal matter resulting in smaller-sized cells. There may also be accumulation of pathogens, or chemical residues from some varroa treatments. Whether it’s for replacing old dark combs or for expanding colonies, there is always a need for frames of drawn-out wax.

In a career that has taken him from mechanical engineering to space craft software, Derek Mitchell returned to earth when his wife took up beekeeping. Looking at the hives that beekeepers used, he was startled because it was at odds with what he knew about heat transfer and therefore what a suitable home for an overwintering colony of insects might look like. So, he set about studying how honey bees operate and where they choose to nest in the wild – often tree trunks. That information made the hive types he saw beekeepers use make even less engineering sense in terms of heat insulation. From initial back-of-the-envelope calculations, he moved into serious scientific study and published an academic paper. Not content with that, he published more papers, six of which now await assessment for the award of a PhD from the Leeds Institute of Thermofluids at the University of Leeds.

Derek knows he is treading in a very contentious area with his controversial findings that run counter to much conventional beekeeping wisdom and previous studies. He is, therefore, at pains to be accurate and to point to evidence and calculations backing up his claims. He thinks that so much of the published research about heat transfer in hives is at best misleading or misdirected, often because it is based on what is happening in beekeepers’ thin-walled boxes, ignoring where bees choose to nest in the wild and how they cope without human intervention.

I met Derek to discuss his ideas as he was preparing for his PhD viva and dealing with the impressive publicity his work has recently had across multiple outlets – from the scientific press to national newspapers. To the layman, fluid thermodynamics is not easy territory, so he tailors his explanations carefully. Crossing disciplines – engineering and biology – he has even met with diverging definitions of particular terms which has posed challenging conversations at times and difficulties in finding funders who have a wide remit. Nonetheless, his ideas have been gaining credence and producing a change in beekeeper behaviour. The bees carry on doing their own thing of course.

As a general rule, he says, the greater the cavity diameter, the thicker the walls need to be to maintain a similar internal heat environment for the bees. For example, creating a tall and narrow hive by turning frames on their sides, simulating the alignment of combs in a tree trunk, is likely to give the bees better insulation.

Skeps, he says, have quite good thermal properties mainly because they taper towards the top. Testing them, he found that if clusters can move up into the narrowing cavity provided by most skeps, the bees are likely to benefit in terms of warmth. The skep material is also likely to be better than the same thickness of wood in slowing down the movement of air/heat outwards. The straw of the skep operates in a similar way to the down in a duvet – the heat moving outwards from the bees hits fibres and has to go around them, thereby slowing down the heat loss. Nonetheless, even this is unlikely to be as good as is likely to happen in a tree trunk.

Timbers differ in their insulating properties. Marine ply is much inferior to cedar in terms of its insulating qualities. The difference between cedar and pine is probably marginal (standardised calculations demonstrate this). Balsa wood might be very good – but the bees would probably gnaw their way through it. Fortunately perhaps for beekeepers’ pockets, mahogany would be very poor for bees because of its high conductivity.

With WB Carr’s thriftiness in creating WBCs, Derek thinks that, if he was alive today, Carr would be searching skips for PIR insulation board (ie, Kingspan/Celotex) to make the WBC lifts (outer walls) and inner walls. Is the inner more important than the outer? It’s the combination of both, says Derek.

This doubled-walled WBC example highlights another complication – where is the condensation happening and can the bees access it?

With a varroa screen in place, the tray needs to be as close to the bees as possible and/or be highly reflective to minimise heat loss. Detritus falling on a reflective tray will absorb heat and counter the effectiveness of the reflective material. Ideally, the varroa screen and the tray should be one unit, like a cassette, and capable of being inserted for varroa counts for a day or two but replaced at other times by a reflective surface which will reradiate any heat from the bees back to the nest. Putting your hand underneath an exposed mesh will convince even the most sceptical of the potential for heat loss.

While insulation in the roof is very important, Derek advises not to forget the end walls where lots of heat is also lost. The old beekeepers’ trick of putting insulation on the sides of National hives is spot on, says Derek. And there is a big clue where to put that insulation – infrared photos of hives in winter usually show the cluster at the front or at the back wall – “That’s the hot spot and that’s where the insulation should go. Long before infrared thermography, the old-timers knew about that.”

Polyhives, plastics aside, offer very good Insulation but, “as with wooden hives, make sure they have small handholds – some have very large handholds and, with this thinning of the hive walls, lots of heat can be lost.”

Dry new honey bee comb is transparent to infrared, but once there has been brood in it (leaving behind moults) or it has held honey (containing proteins and water), it becomes opaque and that can lead to some strange effects. “The heat transfer environment inside the hive can be mind-bending at times. Trying to heat clean dry wax in a microwave is fairly pointless – it may melt but that’s because it has been in contact with its dish which has absorbed the microwave radiation.” Derek is currently working on a paper that includes an analysis of comb spacing and arrangements, but for sound academic reasons cannot speak about that at the moment.

Fluctuating temperatures from cold to warm and back again in winter is more dangerous for bees than consistent cold or consistent warmth, says Derek. The transition from warm to cold requires the bees to expend a lot of energy regulating the nest temperature, so to do this repeatedly endangers the colony. Ironically, he says, it’s best to keep the bees on one side of the ‘transition zone’ or the other. However, keeping them on the cold side is highly stressful and degrades their immune system, so the use of cold storage, as sometimes happens in North America, is flawed and therefore has ethical issues.

Derek has an intriguing take on why a high percentage of swarms don’t make it through winter, even in trees. When bees move into a tree cavity, they must expend a lot of energy to heat up the walls of the nest area. Like a stone cottage left unoccupied and unheated for a long time, the heating required to make the interior comfortably warm can be substantial. Once warmed, however, the insulation can keep it cosy. So, if a vacated cavity is quickly reoccupied by a swarm, the initial heating required is relatively small because of the energy expended by previous occupants. But that’s quite a contrast to moving into a long-vacated cavity which requires complete reheating.

The best time to add insulation to a hive is in spring when the bees have begun foraging and have energy to spare to heat the hive and its insulation without detriment to the colony’s comfort. “At that time, they have the equivalent of money to burn! However, if it’s added in autumn or winter, they then have to direct precious energy to reorganising the nest. There’s a beekeeper in the Yukon who says his bees don’t cluster unless it goes below -40C! Why? Because he insulates the hives so well and there is no top ventilation which would quickly lose heat.”

Now that Derek’s ideas are finding an audience, will beekeeping suppliers rise to the challenge of providing better beehives?  Already, he is being contacted by polyhive manufacturers wanting to know how they can improve their style of hive. Will hive manufacturers move from the ‘leather coat’ insulation which can work in mild conditions to the high-insulation qualities of a down coat?

Photos: Derek Mitchell, Richard Rickitt, Stephen Fleming

The honey bee, Apis mellifera, has existed far longer than humans have been building hives to house them. Before hives were available, and still to this day, honey bees have built their nests in hollow trees and sometimes in other natural cavities, including in the ground, in rock crevices and occasionally not in any kind of cavity. They also commonly nest in cavities in buildings.

Swarms do not select cavities at random. A nest cavity is chosen via a remarkable process carried out by scout bees from a swarm which locate a number of nearby options and of these select a good one (Seeley 2010). They are choosy, rejecting those too small or large in volume, or with entrances that are very small or large. Although bee hives are generally kept at ground level, swarms prefer cavities high above ground.

Swarms can travel several kilometres to a new nest site. Worker bees in swarms have enlarged wax glands and quickly build combs and rear brood from eggs laid by the accompanying queen. The new colony is challenged to build its population and food stores before winter. Many fail. Colonies founded in spring have a higher mortality rate in the following winter than colonies established in previous years.

The Ancient Tree Inventory

The Ancient Tree Inventory (ATI) is a citizen science project started in 2004 by the Woodland Trust (a charity promoting trees and woodlands), the Ancient Tree Forum and the Tree Register of the British Isles. Anyone can register a tree meeting the relevant criteria: ancient and veteran, based on probable age and old-tree characteristics, or notable, such as a good specimen. The listing is then confirmed by an expert and made public. In mid-November 2023 the ATI web site noted that “already more than 190,000 trees [are] listed but there are thousands more to add”.

Trees on the ATI can be referred to as Trees of Special Interest or TSIs but in this article we also refer to them as ATI trees. The ATI is far from complete. Based on a recent study by Nolan et al (2022) with the descriptive title “Distribution models calibrated with independent field data predict 2 million ancient and veteran trees in England”, there are 2 million trees suitable for inclusion on the list in England alone, which is about 15 per square kilometre. Given that England is 53.5% of UK area, there could be 3.7 million such trees in the UK. 

Ancient trees, wildlife, cavities and honey bees

As noted by the Woodland Trust, ancient and veteran trees are a valuable resource for wildlife. Therefore, protecting ancient and veteran trees does more than help just trees and woodlands. As trees get older and larger, they accumulate features valuable to other species. These include cavities, bark with a wider range of textures and pockets where it is partly detached, bark-free areas, deadwood, root buttresses, ivy and other climbers, epiphytes including mosses and lichens, bracket fungi, insect galleries, and in tropical areas termite nests. (For more features see Kraus et al. 2016. Catalogue of tree microhabitats – Reference field list1)

Cavities, the feature honey bee colonies need, take a long time to develop. Only 1% of oak trees, Quercus robur, under 100 years old in southern Sweden had cavities, rising to 50% at 200–300 years and 100% at over 400 years (Ranius et al 2009).

Tree cavities have many causes including fungal decay, which can be promoted by physical damage including that by humans. Some result from excavation by primary nesting animals. The black woodpecker (Dryocopus martius) is Europe’s largest woodpecker, although not found in Britain. It excavates tree cavities commonly occupied by honey bees. However, at approximately 10 litres, these are not quite large enough to accommodate the bees and their winter honey stores. Britain has three woodpecker species. The largest is the green woodpecker (Picus viridis). It makes cavities of approximately 7 litres (15cm wide x 40cm deep). In a study of 21 wild honey bee colonies in New York State, all were in cavities over 10 litres (Seeley and Morse 1976). Research using bait hives showed than cavities of 40 litres were selected over 10 or 200 litres (Seeley and Morse 1978).

Although woodpecker cavities are on the small size, a larger than average cavity or one that has increased in size via decay or by connecting to another cavity, would be a viable home to a honey bee colony. Honey bee workers have small, blunt mandibles adapted for moulding wax but not excavation, so they cannot enlarge a cavity. Many insects, including wood-boring beetle, wood wasp and moth larvae, make tree cavities although these are far too small for honey bee colonies.

LASI survey of ATI Trees

In 2021 and 2022 we surveyed 1052 trees on the ATI at 16 sites in South East England: in East Sussex, West Sussex, Kent, Surrey, and Greater London (Visick and Ratnieks 2023). These were mainly in landed estates with sufficient accessible trees to make surveying practical. Surveys were mainly in early spring, before leafing, to facilitate observing forager bee traffic at nest entrances. To find colonies, trees were scanned by eye and with the aid of binoculars on days and times suitable for foraging. To ensure that the traffic indicated a living colony, not just robbing or scouting, we confirmed that some bees had pollen in their baskets.

How many?

We found 22 honey bee colonies in the 1,052 trees, equivalent to an occupancy of 2% (noting that one tree had two colonies). This suggests that there could be 40,000 honey bee colonies living in ATI trees in England or 75,000 across the UK.

This estimate is based on an extrapolation from a relatively small survey in one part of the UK and should be used with caution. Perhaps interested beekeepers, bee and tree lovers, and naturalists will survey ATI trees in other regions.

The figure could be an overestimate. Maybe ATI trees in South East England have higher occupancy. However, the way in which we surveyed suggests that it may be an underestimate. For one thing, some wild colonies may not have been detected. More importantly, trees were mainly surveyed in early spring, after winter but before swarming. Many honey bee colonies die in winter and early spring with numbers building up in late spring and early summer via swarming. Most wild colonies that survive the winter will swarm, producing one prime swarm and possibly several after-swarms. If we reckon that each surviving colony, on average, makes one or two swarms, then surveys in summer would be expected to find two or three times as many wild colonies.

Of course, wild bee colonies do not only nest in ATI-quality trees. Many will be living in other trees as well as other cavities, particularly in buildings. Overall, this could be a substantial number. There are an estimated 288,000 managed hives in the UK. How many wild colonies are there? We do not know, but it is quite possible that the number of wild colonies is a high proportion, or even equals or exceeds those managed in hives. In another study we reviewed research on the density of wild honey bee colonies worldwide. The results indicate that wild colonies outnumber managed hives two- or three-fold, although in Europe hives outnumbered wild colonies (Visick and Ratnieks 2023). 

A review of the forms and functions of the eight mechanical (non-chemical) signals that worker honey bees produce and that human beings have deciphered.

Imagine that you are a worker bee…

As you begin to read this article, I ask you to imagine that you are a worker bee, and that you have been toiling as a forager but are now resting, perhaps even sleeping, inside your colony’s hive. Suddenly, a peppy nestmate comes along, grabs hold of you with her forelegs, and rapidly shakes her body up and down for a few seconds. You have just received the shaking signal (Diagram 1). Its message is “Hey you. Time to get cracking!” Usually, this signal is produced by active foragers to rouse inactive foragers, but sometimes it is directed at a colony’s queen, to prepare her for departure in a swarm.

Now that you have been shaken, you groom your body to remove the bits of wax that fell onto you while you were resting. To do so, you swipe your antennae using the antenna-cleaner structures on your forelegs, and you brush the wings and undersurfaces of your body using the hairs and combs on your legs. But if you feel a need for cleaning around the bases of your wings (and other places you cannot reach), then you spread your legs widely, grip the comb firmly with all six pairs of tarsal claws, and (for a few seconds) rock your body side to side at a frequency of about four rocks per second. You are performing the grooming invitation dance (Diagram 2). Almost always, and within just a few seconds, a hive mate will turn to you and start cleaning – by nibbling – the hard-to-reach places on your body.

A minute or so later, you are ready to resume work as a forager. Now you walk to the dance-floor region in your colony’s nest – the areas of comb just inside its entrance – and then you either depart for the flower patch you visited the day before or linger to follow a waggle dance (Diagram 3). Doing the latter might stimulate you to resume work at your former flower patch or it might steer you to work at a new one.

Now, imagine that you have worked at a patch of flowers laden with rich nectar and are coming home highly excited by your foraging success. If you scurry inside the hive and are met in less than 15 seconds by a hive mate functioning as a nectar receiver, then you will advertise this flower patch by performing a waggle dance. But if you scurry inside and must search 60 seconds or more to find a hive mate that is willing to receive your nectar, then you will perform a tremble dance (Diagram 4). You will produce this signal because the rather long unloading delay that you just experienced has informed you that your colony needs to activate more of its middle-aged members to function as nectar receivers. Your tremble dance is a ‘call’ for bees to fill this need. To fully exploit the honey flow, your colony needs many workers to perform the tasks of receiving, processing and storing the flood of fresh nectar that its foragers are bringing home.

And now, imagine you are a nest-site scout

At this point, dear reader, I need you to switch to imagining that you are a worker bee that is functioning as a nest-site scout. The first two signals that you will produce in this role are worker piping (Diagram 5) and buzz running (Diagram 6). At first, you produce these signals inside your home. You produce piping signals to tell your nestmates to warm their flight muscles in preparation for their mass exodus in a swarm. Then, when you sense that your nest mates have their flight muscles sufficiently warmed up, you produce buzz runs to trigger the explosive departure of some 10,000 bees, including your queen, from your home. From start to finish, the exodus of your colony’s swarm takes only a minute or two.

After the swarm bees have settled into a cluster on a nearby object (such as a tree branch or a stop sign), you and your fellow nest-site scouts use two signals to conduct the collective decision-making process to choose which one of several potential home sites is best for your group’s future home. One of these signals is well known to your beekeeper: the waggle dance. 


S/he knows that you use this signal to advertise profitable food sources and desirable home sites. The other signal is the stop signal (Diagram 7). It is not so well known. This is because the biologists who study your behaviour discovered this signal only recently. This is a very brief (c150 milliseconds) vibrational signal with a frequency of about 350 cycles per second, and is delivered by you momentarily butting your head against a waggle dancer. You use this signal to inhibit waggle dancing to advertise potential nest sites other than the one that you favour. The stop signal creates cross-inhibition between the groups of nest-site scouts advertising different possible home sites, and this helps you and your fellow nest-site scouts avoid the problem of coming to a split decision over two equally good sites.

Once you and the other nest-site scouts have reached a decision, you again use your worker piping and buzz-run signals to stimulate the swarm to warm up and launch into flight to move to its new home site. When every bee is airborne, you produce signals of another sort to steer the movement of the airborne swarm: streaker flights (Diagram 8). These are the high-speed (c35km/hr) flights that you and your fellow scouts make through the top of the swarm cloud. They point in the direction of the new dwelling place. It remains a mystery, however, how you scout bees apply the brakes to your swarm’s cloud of swirling bees as it approaches its destination so that it stops right at your new home site. Indeed, there is much about your communication skills that begs further investigation by inquisitive humans.

Who you buzzin′ round now Billy bee, Billy bee
Who you buzzin′ round now?
Why you buzzin′ round her not me?
The Haden Triplets

The honey bee genus Apis includes at least a dozen species. Among these, only the western honey bee (Apis mellifera) occurs in Europe. More than 30 subspecies are found there and in Africa and the Near and Middle East (Table 1 in Carr, 2023). Honey gathering is depicted in petroglyphs from the Iberian Peninsula 8,000 years ago, and apiculture is well documented in Egypt as far back as 2600BCE. From their Old World origins, western honey bees have been transported around the world as a source of honey and beeswax, and in the Americas as pollinators of vegetable and fruit crops that have also been imported from elsewhere. Geographic variation among different local subspecies of A. mellifera is known to contribute to the quality and quantity of honey produced, their use as pollinators and other behaviours.

There is thus a great deal of practical interest in understanding the genetic variation and evolutionary history of honey bees. But first an admission: apart from a single course in entomology as a biology undergraduate, I know almost nothing about bees and beekeeping. My specialisation is genetics and evolution, and I want to tell this story as an example of a typical scientific investigation. This is what I found.

Morphological studies of honey bee subspecies have recognised four continental groups, designated ACMO: African, Continental (European), Mellifera, and Oriental (Near and Middle Eastern). The nucDNA (explained below) genome agreed broadly with this arrangement and suggested an ‘Out of Africa’ hypothesis (Diagram 3) with two invasions of Europe and Asia from Africa (plus ‘Africanised’ bees in the New World). An alternative ‘Out of Asia’ hypothesis looked at the same data, but proposed invasions of Europe and Africa from Asia.

How it’s done

What would I find if I started over from scratch? First, I have to tell you about a particular DNA molecule, mitochondrial DNA (mtDNA), a small, circular molecule found outside the cell nucleus in the power-generating mitochondria, where its dozen or so genes contribute to cellular metabolism. Unlike biparentally inherited nuclear DNA (nucDNA), the mtDNA genome is inherited solely through the maternal line: mothers pass it to all their offspring, but only the daughters pass it to their offspring, and so on. MtDNA was the first DNA molecule to be used in the reconstruction of evolutionary trees and, as it evolves much more rapidly than nucDNA, it is very good at tracing evolutionary lineages over shorter evolutionary times. It’s worked well in my own studies of human populations, other mammals, fish and the occasional sea monster (tinyurl.com/BC2023-12-01).

As a scientific editor, I was asked to review a paper on the use of variation in short mtDNA molecules to identify honey bees. To check the authors’ conclusions, I began to make a more complete meta-analysis, an assembly of data from previous authors into a single, comprehensive analysis. To that end, I compiled the complete mtDNA genome sequences of nearly 100 individual bees from nine species of Apis, including 22 subspecies of A. mellifera. This is just short of one million DNA base pairs (ACGT letters) (Diagram 1).

Phylogenetics, the use of genetic data (such as mtDNA genome sequences) to reconstruct the evolutionary history (phylogeny) of species, can be based on different assumptions and models about how DNA evolves. They all start by identifying all nucleotide changes in the ACGT codes among individuals, subspecies and species: these are called single-nucleotide polymorphisms (SNPs) or snips.

The data for this meta-analysis come from an online database of DNA sequences, GenBank, which includes all DNA sequences published in the scientific literature. The genus Apis can be seen in the Taxonomy Database: tinyurl.com/BC2023-12-02. Like museum collections of pinned insects and skinned animals, GenBank is curated. Entries for individual DNA sequences (accessions) include a lot of molecular information. Does it code for a protein? Where do the coding regions start and stop? How are multiple genes in a single mtDNA genome organised? Also included is information about the source of the specimen. For example, curation for GenBank accession KY926884.1, my reference sequence of A. m. mellifera, includes as below.

/organism = “Apis mellifera mellifera”
/sub_species = “mellifera”
/specimen_voucher = “1410”
/country = “Norway”
/collected_by = “Prof. F. Ruttner”
/note = “stored at Ruttner Bee Collection at the Bee Research Institute at Oberursel, Germany”

Much like the record for a specimen in a museum case, this links that specimen with the molecular data.

The analysis proceeded in three stages. First, I used the mtDNA of a bumblebee (Bombus ignites) to sort out the phylogeny of nine species of Apis honey bees. I used several methods of reconstruction (see Panel). This confirmed previous studies that the so-called cavity-nesting species including A. mellifera and A. cerana (the Indian honey bee) are most recently evolved from the dwarf and giant honey bees, and that A. mellifera is the earliest group to diverge from the other cavity nesters.

Next, I made some trial runs with just a few specimens and subspecies of A. mellifera at a time, with A. cerana to sort out relationships.

The third stage was to assemble all the mtDNA genomes from every subspecies available (22) with as many replicate sequences from different individuals in the same subspecies (80) into a single evolutionary tree (see Figure 2 of Carr 2023).

Things Fall Apart with Out of Africa versus a Scramble for Africa

The meta-analysis offers a radically new molecular phylogeography (genetic relationships in their geographic context) for subspecies of A. mellifera (Diagram 2). The ancestral A. m. mellifera originated in northern Europe, diversified in Southeastern Europe, expanded into Asia Minor. European bees then spread southward via the Levant into the Nile Valley and across the Red Sea down the Yemeni coast of the Arabian Peninsula. Southward expansion left distinct Ethiopian and insular Malagasy subspecies. Sub-Saharan African forms are part of a single lineage. Mediterranean honey bees are a secondary return, first to the Iberian Peninsula and thence to the western islands and coastal African oases.

Divergence times among animal taxa can be estimated from a molecular clock, based on the observation that molecular differences and time of divergence are closely correlated. Use of a standard calibration for insect mtDNA suggests that the genus Apis diversified in the late Miocene (c16 million years ago). A. mellifera diverged from other cavity-nesters during the late Pleistocene (c800,000 years ago) at about the same time as Neanderthals diverged from anatomically modern humans. Separation of Euro-African lineages from Sub-Saharan lineages was as recently as 250,000 years ago. Diversity in the Mediterranean group may have been influenced by the most recent Ice Age, c20,000 years ago.

Some of the main differences between the Out of Africa and the Scramble for Africa hypotheses are summarised in Diagram 4. No MA+OC (Mellifera-Africa + Asia Minor-Continental) model places European bees as basal to African subspecies, whereas the mtDNA data place the latter as the latest products of A. mellifera evolution. The MA+OC model scatters closely related, geographically contiguous subspecies within the Mediterranean mtDNA clade (a group with a common ancestor), including Iberian and North African oasis forms, over the M, A and C clusters.

Similarly, the continuous distribution of Syrian, Yemeni, and Nile Valley subspecies in the mtDNA data are dispersed over the A (Africa) and O (Asia Minor and Caucasian) clusters. On the other hand, groupings of C (Continental European) and O subspecies are similar in both models.

The MA+OC model tends to support the classic morphological picture as a separation among continents. The mtDNA-based model instead describes successive movement across and between continents that are of multiple origin, such that honey bees in Europe, Asia (Near and Middle Eastern) and Africa are of multiple origin.

What to make of these differences? Contrasts between nucDNA, mtDNA and even morphological phylogenies are not unknown. Hybridisation between adjacent subspecies of honey bees may offer an explanation. A queen of one subspecies, arriving in a new area, where she is courted by drones of a different subspecies, will combine her mtDNA with the nucDNA of both species. Recruitment of her hybrid offspring as new queens, with her mtDNA and mixed nucDNA, can allow the mtDNA to jump the subspecies boundary if successive generations continue to backcross to local drones. North African queens newly arrived in Iberia may offer a model. There are some cool experiments here.

“You’ve no idea how confusing it is ….”

”I don’t think they play at all fairly,” Alice began, in rather a complaining tone, “and they all quarrel so dreadfully one can’t hear oneself speak – and they don’t seem to have any rules in particular: at least, if there are, nobody attends to them – and you’ve no idea how confusing it is all the things being alive.”

Lewis Carroll’s Alice’s Adventures in Wonderland

Conclusions:

Working melittologists (beekeepers) may take home some general conclusions about genetics.

1. “I don’t know anything about this, but I’ll tell you what I think.” Meta-analysis is a useful method of rechecking previous conclusions as new data become available. Methods of molecular systematics are the same across taxa. Traditional taxon-specific knowledge remains important and together with increasingly sophisticated molecular approaches may lead to crucial new insights.

2. “Get a second opinion.” Many of the Apis subspecies examined are represented by a single specimen. Duplicates begin to reveal more complex patterns and even errors. DNA sequencing used to be difficult and time-consuming. Now that it’s much easier, identifications should be checked by multiple specimens.

3.  “Don’t believe everything you read.” Consultation of the original literature on honey bee systematics as well as the GenBank database should be done with a critical eye. Systematics evolves.

4. “Names Matter.” Even in the 21st century, so-called ‘Alpha Taxonomy’, the basic science of recognising different forms of creatures, remains important, even in well-studied taxa like Apis.

5.  “DNA does not lie.” When I began my graduate work in genetics, knowing the complete ACGT code of any complex species was an impossibly far-off dream. A few decades later, this is a routine operation of a few days work for a few thousand dollars. The newly emerging science of bioinformatics requires proper curation, improved methods of information science and novel approaches to analysis in order to understand and make efficient use of the vast amounts of data now available.

Bees feed primarily on pollen and nectar provided by flowers. Unfortunately, agricultural intensification, urbanisation, land conversion and other factors have reduced flower abundance. One obvious way to counteract this decline is simply to make more flowers available, particularly in the summer when floral resources are in short supply relative to the needs of honey bees, other bees and flower-visiting insects (Ratnieks & Harris, BeeCraft, August 2023).

So, how can we cause there to be more flowers? Planting flowers seems an obvious solution but is difficult on a grand scale, although there are schemes to incentivise farmers to provide additional flowers on farmland. In August 2023, the UK Government started a Sustainable Farming Initiative (SFI) to incentivise many things relating to the environmental stewardship and wildlife conservation in agricultural land. This makes sense given that most (71%) of the UK area is agricultural land and has large effects on water resources, greenhouse gas production and capture, biodiversity, not to mention food production and food security. The National Farmers Union (NFU) seems generally positive about the SFI and has produced a helpful list of the incentives, some of which are relevant to bee food supply including hedgerows, buffer strips in arable and pasture fields, grass leys with flowers including clover and so on.

Examples

Underappreciated bee-friendly native wildflowers

Ivy is a very common and well-known climbing plant in Britain and much of Europe. In Sussex, and probably the rest of Britain and Ireland, it is the main source of autumn nectar and pollen. This is because it is both widespread and abundant and because its open flowers make the nectar and pollen accessible to all insects. Even insects with short tongues can gather ivy nectar, unlike plants such as lavender that secrete nectar at the base of a long flower tube accessible mainly to longer-tongued insects like bumblebees and butterflies. Honey bees can struggle to access lavender nectar (Balfour, Garbuzov & Ratnieks, 2013).

Ivy is visited by all autumn-active flower-visiting insects, including honey bees, ivy bees, bumblebees, hover flies, other flies, butterflies and wasps. Pollen traps we put onto hives in Sussex, southern England, showed that 90% of the pollen collected in autumn was from ivy (Garbuzov & Ratnieks 2014b; Hennessy et al 2021). Ivy grows on walls, tree trunks and in hedges, and is abundant in both rural and urban areas. However, ivy suffers from misguided concerns that it parasitises the trees that it climbs. In fact, ivy only uses the tree for support and its own roots are in the ground. Ivy is a true native wild plant. Birds eat its berries as winter food and disperse its seeds in their droppings. As a result, ivy can spring up almost anywhere. If ivy were to disappear, it would surely be catastrophic for autumn-flying flower-visiting insects. (See also August BeeCraft.)

Bramble, also called blackberry, has parallels with ivy. It is abundant in both urban and rural areas, has seeds dispersed by birds and mammals, and has open flowers that are accessible to all types of insects. In Sussex, bramble blooms for a long period, typically starting in late May and continuing throughout summer and even into autumn, with peak bloom in June. Pollen traps we put on hives in Sussex showed that 31% of the pollen collected from late May to early August was from bramble (Wignall et al 2020).

Dandelions and white clover are native wildflower species that provide pollen and nectar. Both are often found in lawns but are not always appreciated. Garden centres sell herbicides for these and other lawn ‘weeds’ (Wignall et al 2023). White clover is unusual because it is also an agricultural crop. It is often sown with grass seed in pastures to improve soil fertility. White clover and many related species in the bean family house bacteria in special root nodules. The plant provides the bacteria with energy and the bacteria convert the nitrogen in the air into a form that plants can utilise (Harris & Ratnieks 2021). It is one of Britain’s most important nectar sources (Williams, Carreck & Little 1993). 

In Britain, five species of native wildflower are officially termed injurious weeds. These are technically illegal to have on your land. Two are docks (Rumex) that are mainly wind pollinated and so do not attract flower-visiting insects. The other three are ragwort and two species of thistle. They are very common in road verges, fields and waste land. We compared the numbers of flower-visiting insects on these three species with 14 other wildflower species growing beside them in pasture fields in Sussex. These other species were officially recommended as good for pollinators. On average, the injurious weeds had twice as many insects. In addition, they have more insect species that feed on their leaves (Balfour & Ratnieks 2022).

Local views of wildflowers in a suburban park

LASI carried out a study at a local park, the Saltdean Oval in Brighton, with encouraging results that showed both how simple it can sometimes be to encourage existing wildflowers and also the positive responses of park users (Garbuzov et al 2015).

The park had been mown for many years to keep the grass short. Subsequently, the local council’s parks department cut half only once per year. This became ‘long grass’. But it was not just grass. Many native wildflowers were already growing among the grass. The mowing had not killed them but had greatly reduced their bloom. Without any planting, they were now able to bloom profusely in the long grass area resulting in a remarkable display of colour.

We made counts of flower-visiting insects and found that there were 50 times as many in the long-grass area than the short-grass area. This was a good result for the flowers and the insects. But what did the public using the park think?

By interviewing park users, we found that the most popular recreation activities were to relax (42%), walk (42%), walk the dog (63%), take children to play (45%), look at plants (18%), look at insects (21%) and ‘other’ 8%. (Many people did more than one thing.) Importantly, looking at plants and insects were popular.

Most people (61%) had noticed the change in management, the wildflowers in the long grass (72%) and also bees or butterflies (79%). Almost all (97%) thought it was good to encourage insects and wildflowers. Most (74%) said that the amount of long grass was appropriate, some (23%) said it was too much, and 3% too little. As we all know, you cannot please everyone but over three times more respondents were happy than not.

These results show that many local park users enjoyed looking at nature in the park including flowers and insects, noticed what was going on and supported efforts to help nature. A key reason that most people were happy was no doubt because half the park remained as short grass. This gave ample space for activities such as ball games and strolling.

Improving appreciation and encouragement

Local wildflowers: do they need their own name or term?

Nowadays, the word wildflower is often used to sell seed mixes that can include non-native species. These may be wildflowers in some part of the world, such as the North American prairies, but often they are not wildflowers where they are planted. In other cases, they may be native species but with seed gathered in a different country. True wildflowers are those native to the local area. Planting ‘wildflower’ seeds is much the same as planting out an area with bedding plants, and indeed considerable time and effort must be spent preparing the ground to receive the seeds. In addition, many of these ‘wildflowers’ are annuals giving a burst of colour that declines in subsequent years. By contrast, many bee-friendly wildflowers are perennials.

Wildflowers in a suburban lawn

Even a small patch of garden, lawn, field edge, or roadside might have multiple wildflower species that bees and insects will visit when in bloom. In late June, we studied a small patch (161m2) of lawn that had been uncut for two weeks in a suburban garden in Uckfield, a small town in Sussex, (Ratnieks & Flockhart 2020). In bloom were ten native species, none of which had been planted. Six were abundant and four (white clover, red clover, bird’s-foot trefoil, selfheal) had numerous foraging bees and flower-visiting insects.

Promotion and education

One challenge in appreciating these true local wildflowers may be that there is no word or term for them. Given that the word wildflower has been somewhat usurped by people trying to sell seeds that are not native wildflowers, there appears to be a need for a suitable word or term specifically for them. Maybe we need a competition or a campaign to select or popularise one. ‘Local native wildflower’ or simply ‘local native’ convey the key idea. But is it too clumsy or ill-defined? What better term could be used?

Is a lawn with wildflowers in addition to grass attractive or ugly? Is it a sign of a lazy person or someone who is encouraging nature? Is it something to enjoy and celebrate or to criticise? It is certainly easier, cheaper and probably safer to enjoy the existing wildflowers in a lawn than to go to the cost and trouble of removing them with herbicides, and especially to pay a ‘lawn care’ company to do it for you.

Long grass is probably not suitable for most domestic gardens, unless the lawn is large. But it is an option for roadsides and parks, as the example of the Saltdean Oval showed. One challenge with long grass is that it can give the impression that the landowner or council is not managing the area properly. One way round this is to mow paths to ‘frame’ the long grass areas to show that it is being managed and to ease access.

Education, in the broadest sense, might help to increase public appreciation of local native wildflowers. This could be via almost any method, whether formal or informal, and to any age group, including school pupils. Educating the public to appreciate local native wildflowers has every chance of success. Many people probably do not realise that there already are wildflowers everywhere, and this would be a good place to start. They do not have to be expensively planted using commercial seeds (probably sourced from other countries or even of non-native species) after preparing the soil. The study at the Saltdean Oval showed that encouraging the local native wildflowers already present was simple and popular. No planting was needed, and the only management was simply mowing less often.

Many underappreciated local native wildflowers already have signs of appreciation beyond their value as nectar and pollen sources to bees and other insects. Blackberries are probably the most widely eaten of all wild foods in Britain. Ivy is liked because it is evergreen. It is also a girl’s name which shows the high esteem it is held in. Spear thistle (Cirsium vulgare), one of the injurious weeds, is the national flower of Scotland. Ragwort was eulogised by English poet John Clare (1793-1864) in his poem The Ragwort: “Ragwort, thou humble flower with tattered leaves/I love to see thee come and litter gold …”. Many of the local native wildfowers that will grow in lawns are beautiful individually and can even result in spectacular displays in which a lawn becomes white, yellow or blue. 

Appreciating local native wildflowers will likely also convey psychological benefits by helping people connect to plants and nature. Indeed, knowledge about native plants seems to be at a low ebb in Britain. A study of A-level pupils (final two years of high school) found that 86% could name only three or fewer common wildflowers, and a poll commissioned by the UK conservation charity Plantlife found that only 3.5% of British participants were able to name red clover correctly. These figures show the disconnect between people and plants. The term ‘plant blindness’ has been coined to describe “an inability to notice or appreciate plants, distinguish among species or recognise their importance”. Given that bees and flower-visiting insects depend on flowers, and that most life on Earth depends directly or indirectly on plants, this is surely not a good thing (Wignall et al 2023). 

What can beekeepers do?

Local native wildflowers help bees and other flower-visiting insects. They don’t need planting as they are already widespread. What they really need is to be better appreciated and encouraged. We don’t need to plant more ivy, bramble or dandelions, or to encourage weeds. But where these plants grow, and especially where they bloom, perhaps we can leave them be. In some cases, it may take a change in attitude and a relaxation of the urge many people feel to be excessively tidy. Beekeepers benefit directly from wildflowers and are one group of people who should be at the forefront in educating others.

Clare Densley and Martin Hann from Buckfast answer your beekeeping queries.

Clare  This sounds very similar to my second year as a beekeeper. I do remember the sense of achievement I felt hiving my first swarm, and also my feelings of utter failure when I lost my first colony over winter. However, to address your first question: I don’t think that you have a particularly swarmy line of bees just because they swarmed multiple times.

Martin  It’s normal for a strong colony to follow the prime swarm (the first one) with a series of cast swarms during a good year. The reasons a colony swarms may be many, and too complicated to detail here, so let’s just say that your colony was strong before it swarmed. There were lots of bees, lots of brood, lots of food and lots of queen cells. Swarming is colony reproduction. Each swarm which leaves the hive is an insurance policy in case some of them don’t make it. They aren’t all expected to survive, but if a few do, the collective genes of the colony will be passed on into the next generation.

Clare  I learned that the first virgin emerging after the prime swarm left would kill the remaining virgins in their cells.

Martin  I learned that too. I also remember thinking that if half the colony had gone off with the swarm, there wouldn’t be enough bees for them to swarm again.

Clare  It’s incredible how quickly the colony population replenishes after a swarm leaves. Before the swarm departs, there is usually a large amount of sealed brood on the verge of emerging. So, I don’t think that you have particularly swarmy bees. In some years this is normal.

Martin  If you don’t want the hive to carry on swarming, you will need to cull the superfluous cells and leave just one. This is probably a better strategy than catching all the small cast swarms and putting them in separate hives. Remember that you will need to do a second cull of queen cells about a week later in case they make emergency cells – you can read up about why they make these.

Clare  Alternatively, you could dump all the casts into one hive and let them sort it out. You can add cast swarms as they come out over a period of time. They will have a better chance of survival as a larger unit than as lots of small colonies. There may be a bit of fighting, but eventually they will sort it out and the resulting colony may be robust enough to get through the winter if the remaining virgin mates successfully.

Martin  So, to the second part of your question. The original colony will be left with a single virgin which has to get mated. Looking at the photo there seem to be only capped drone cells so it seems yours didn’t mate successfully and so it became a drone layer. There isn’t much you can do to help it because it’s dwindled down to almost nothing. Let her go!

Clare  You still have two good colonies – the one with your original queen (the first swarm you hived) and a cast swarm colony. So start the season by making sure that they are looked after and given plenty of space early enough in spring. This won’t prevent swarming – there are lots of reasons for this – but it will stop them from doing it because of overcrowding. Clean up the gear from your dead-out and read up about swarming. Wally Shaw’s books: An Apiary Guide to Swarm Control (published by Northern Bee books) and Swarming biology and Control (published by Bee Craft) are excellent.

Martin  There are two species of wax moth, Achroia grisella, the lesser wax moth, and Galleria mellonella, the greater wax moth. Both can be serious pests in beehives, being responsible for the destruction of wax combs particularly in weaker colonies or stored supers. It’s only the larval stage which is responsible for this damage as the adults are unable to feed due to their atrophied mouthparts.

Clare  You mean the moths don’t eat anything?

Martin   This is common for lots of insects. Mayflies only live for 24 hours; they don’t have any mouthparts and so they just mate; the females lay eggs and then they die.

Clare  So, the larval stage is the part of their lifecycle where they eat and grow before metamorphosis?

Martin  The larvae consume honey, nectar, pollen, and beeswax as they eat their way through the combs. They tend to go for ones which had brood in them because of the protein-rich remains of honey bee pupal skins – and poo – left behind when they moult. The speed of the lifecycle from larvae to moth depends on the quality of this nutrition and the temperature of the environment, anything from four weeks to six months.

Clare  I read somewhere that wax moth larvae don’t infest clean wax, but I’ve seen the telltale frass, the digestive waste, on unused foundation and even on some wax candles and ornaments we have on our shelves.

Martin  While they are able to survive on a clean wax diet, they need the protein from the honey bee larvae skins that are shed and the cocoons embedded in the brood cells to allow them
to pupate.

Clare  Why do they appear to eat into the wood of the hive bodies then? Are they digesting that too?

Martin  Wood is a composite material comprising cellulose fibres and lignin. There are many insect species whose larval stage feeds on wood, but they only digest the cellulose part. However, some of them deconstruct the lignin either mechanically or chemically to get to the cellulose. When wax moth larvae faecal matter was examined, it was found to contain a majority of lignin suggesting that it passed straight through them mainly undigested.

Clare  So, this little boat shaped furrow seems to be just a kind of cradle for the cocoon to be attached to, and the wood excavated by the larvae passes through them unchanged? Really, it’s just a means to an end rather than a food source.

Martin  I suppose there would be plenty of protected cracks and fissures for the larvae to nestle into before spinning their silk cocoons in a tree cavity, but a smooth walled hive obviously needs some modification to achieve this.

Clare  I’ve heard that they could eat plastic.

Martin  There’s some well-publicised research from Brandon University in Canada about the wax moth larvae’s ability to digest some plastics by using enzymes in their saliva. It may seem odd to us that any creature can gain some nutritional benefit from plastic, but apparently, it’s all to do with the CH2-CH2 bond. My organic chemistry is pretty rusty but this type of bond which is found in polyethylene plastic is the same (or very similar) to that found in beeswax.

Clare  An update on that research says that, although they can break down plastic by oxidising the molecules, they don’t actually gain any nutritional benefit from it and so aren’t technically eating it – just modifying it. If they were just given this as sustenance, they would fade away and die from malnutrition. Do you think that they actually eat wax, or is it just being modified and passing through in the same way as polythene or lignin?

Martin  You mean the larval moults and poo is the main nutrition for them, not the actual wax?

Clare  Yes. I’ve just found a paper which suggests this.

Martin  To be fair, the wax moth damage in clean beeswax is never extensive, just annoying.

Further reading

www.nature.com/articles/s41467-022-33127-w

www.one5c.com/plastic-eating-worms-136931560

www.beelistener.co.uk/diseases/honey-bee-pests-lesser-wax-moths

In July, 12 beekeepers attended the Advanced Beekeeping Course run by the National Diploma of Beekeeping (NDB) at Pershore College in Worcestershire. One of their exercises was to compare different methods of monitoring the number of varroa in a colony. BeeCraft was invited to observe the process and its results.

To compare varroa-monitoring techniques, the beekeepers on the course were split into four groups, each of which performed the same five monitoring methods on comparable full-size production colonies, sharing and reviewing their results at the end of the exercise. The following methodologies were used.

Results and conclusions

At the end of the exercise, the NDB students returned to the classroom to compare results and discuss the methods. Relatively few varroa were found and this was considered a credit to the beekeeper at Pershore, Rhona Toft, who has long selected for varroa-coping abilities in her bees and has not treated them since 2016. 

It was felt that on this occasion the alcohol wash and icing sugar methods were the most effective at separating varroa from a sample of bees. Some people were uneasy about the alcohol method because it killed the bees, although it was considered that the loss of 300 bees would not adversely affect a healthy colony. However, killing the bees does allow them to be carefully counted, giving a more accurate indication of the sample size than with other methods. Some of the group used the camera and magnifying function on their phone to help with the count. The alcohol wash method is slightly more expensive because it uses isopropanol instead of icing sugar. Both methods were considered to be more effective and better value than the CO2 method, which uses relatively costly equipment and materials. The advantage of all three methods is their efficiency, allowing varroa levels to be monitored quickly and at short notice. 

Bob Smith NDB, one of the tutors on the course and formerly a research chemist, stressed the importance of high-quality sampling. With one exception, each of the tests used samples of bees gathered from a small part of the colony – typically a single brood frame. 

The natural drop method, on the other hand, counts mites falling from bees on all of the frames in a hive and over an extended period, therefore probably providing a more representative sample. Indeed, this method indicated the presence of varroa in every colony when in some cases other techniques produced no evidence at all. 

It was suggested that the pattern of mites falling from a colony can change depending on the activities of the bees (during a flow they might spend less time preening, for example), so using the natural drop method frequently and for a minimum of seven successive days will give a more balanced result. Course tutor Lynfa Davies pointed out that various predators can remove fallen varroa, so it is worth counting the fallen mites and cleaning the board several times, adding the counts to get a total for the seven days. Overall, the natural drop method was considered one of the more effective techniques. 

The drone brood uncapping technique was considered effective but required the most skill, both in identifying brood of the right age and in levering it out of the comb. One advantage is that this technique can be combined with a biotechnical varroa control method, cutting the whole the slab of drone comb from below a brood frame to remove the varroa it contains from the colony.  

Interpreting the results

There was considerable discussion about how the varroa counts indicated infestation levels or the need to treat a colony. Commercially available equipment usually comes with instructions indicating various thresholds, although they are somewhat variable.

The simplest results to interpret were from the drone brood uncapping and natural mite drop techniques since both methods are recommended by the National Bee Unit (NBU) and details of the methods and how to analyse and act on results are given on its BeeBase website (www.nationalbeeunit.com).

The overall conclusion was that varroa monitoring is not very rigorous and it that it probably doesn’t matter which method you use. The key is to monitor colonies consistently compare like-for-like results to give a sense of varroa infestation as it changes throughout the season.