Category Archives: Problems

The waggle dance

Ask a non-beekeeper what they know about bees and you’ll probably get answers that involve honey or stings.

Press them a little bit more about what they know about other than honey and stings and some will mention the ‘waggle dance’. 

Karl von Frisch

That the waggle dance is such a well-known feature of honey bee biology is probably explained by two (related) things; it involves a relatively complex form of communication in a non-human animal, and because Karl von Frisch – the scientist who decoded the waggle dance – received the Nobel Prize 1 for his studies in 1973.

Von Frisch did not discover the waggle dance. Nicholas Unhoch described the dance at least a century before Von Frisch decoded the movement, and Ernst Spitzner – 35 years earlier still – observed dancing bees and suggested they were communicating odours of food resources available in the environment.

Inevitably, Aristotle also made a contribution. He described flower constancy 2 and suggested that foragers could communicate this to other bees.

Language and communication are important. The development of language in early humans almost certainly contributed to the evolution of our culture, society and technology. Communication in non-human animals, from the chirping of grasshoppers to the singing of whales, is of interest to scientists and non-scientists alike.

It is therefore unsurprising that the ‘dance language’ of honey bees is also of great interest. Although not a ‘language’ in the true sense of the word, Von Frisch described the symbolic language of bees as “the most astounding example of non-primate communication that we know” over 50 years ago. This still applies.

The waggle dance

The waggle dance usually takes place in the dark on the vertical face of a comb in the brood nest, usually close to the nest entrance. The dance is performed by a successful forager i.e. one that has located a good source of pollen, nectar or water, and provides information on the presence, the quality, identity, direction and distance of the source, so enabling nest-mates to find and exploit it.

The dance consists of two phases:

  1. The figure of eight-shaped ‘return phase’ in which the bee circles back, alternately clockwise and anticlockwise, to the start of …
  2. The ‘waggle phase’, which is a short linear run in which the dancer vigorously waggles her abdomen from side to side.

The direction of the food source is indicated by the angle of the waggle phase from gravity i.e. a vertical line down the face of the comb. This angle (α in the figure below) indicates the bearing from the direction of the sun that needs to be followed to reach the food source. 

For example, if the dancer performs a waggle phase vertically down the face of the comb, the food source must be opposite the current position of the sun.

The waggle dance

The distance information is conveyed by the duration of the waggle phase. The longer this run is, the more distant the source. A run of 1 second duration indicates the food source is about 1 kilometre away.

The quality of the food source is indicated by the vigour of the waggling during the waggle phase and the speed with which the return phase is conducted. 

Surely it can’t be that simple?

Yes, it can.

What I’ve described above allows you to interpret the waggle dance sufficiently well to know where your bees are foraging.

Next time you lift a frame from a hive and see a dancing bee, circling around in a little cleared ‘dance floor’ surrounded by a group of attentive workers, try and decode the dance.

Remember that the dance is performed with relation to gravity in the darkened hive. You’re looking to identify the angle from a vertical line up the face of the brood comb to determine the direction from the sun.

Time a few waggle phases (one elephant, two elephants etc.) and you’ll know how far away the food source is.

Really, it’s that simple?

Of course not 😉

The waggle dance was decoded more than half a century ago and remains an active subject for researchers interested in animal communication.

What you’ll miss in your observations is an indication of the type of nectar or pollen resource that the dancing bee is communicating. The dancing worker carries the odour of the food source and may also regurgitate nectar, presumably helping those ‘watching’ (remember, it’s dark … nothing to see here!) determine the type of resource to look for when they leave the hive.

You will also be unable to detect the pulsed thoracic vibrations that the dancing bee produces. These are also indicators of the quality of the food source; better (e.g. higher sucrose content) resources elicit increased pulse duration, velocity amplitude and duty cycle, though the number of pulses is related to the duration of the waggle phase, and so is another potential indicator of distance.

Inevitably, there are also pheromones involved.

There always are 😉

The dancing bee produces two alkanes, tricosane and pentacosane, and two alkenes, Z-(9)-tricosene and Z-(9)-pentacosene. These appear to stimulate foraging activity 3.

But it’s cloudy … or rain stops play … or nighttime

What happens to dancing bees if foraging is interrupted, for example by poor weather or night? 

The dancing bee continues to change the angle of the waggle phase as the sun moves across the sky. This means that a dancing bee will correctly signal the direction to the food source, even if they have not left the hive for several hours.

During their initial orientation flights they learn the sun’s azimuth as a function of the time of day, and use this to compensate for the sun’s time-dependent movement.

Some bees even dance during the night, in which case the watching workers must presumably make their own compensations for the time that has elapsed since the dance 4.

And what happens if the sun is obscured … by clouds, or buildings or dense woodland? How can those directions be followed?

Under these circumstances the foraging bee detects the position of the sun by the pattern of polarised light in the sky. 

Scout bees

The waggle dance is also performed by scout bees on the surface of a bivouacked swarm. In this instance it is used to communicate the quality, direction and distance of a new potential nest site. 

Swarm of bees

Swarm of bees

The intended audience in this instance are other scout bees, rather than the general forager population 5. These scouts use a quorum decision making process to determine the ‘best’ nest site in the area to which the bivouacked swarm eventually relocates.

The shape of the bivouac often lacks a true vertical surface. However, since it’s in the open the dancing bees can orientate the waggle run directly with relation to the sun’s direction, rather than to gravity.

Under experimental conditions the dancing bee can communicate the presence and quality of a food source on a horizontal comb, but – with no reference to gravity – all directional information is lost 6.

The round dance

The duration of the waggle phase is related to the distance from the nest to the food source. Therefore the recognisable waggle dance tends to get difficult to interpret for sources very close to the nest.

It used to be thought that there was a distinct directionless dance (the ’round dance’) for these nearby i.e. 10-40 metres, food sources. However, more recent study 7 suggests that dancers were able to convey both distance and direction information irrespective of the separation of nest and food source. This indicates that bees have just one type of dance for forager recruitment, the waggle dance.

Do all bees communicate using a waggle dance?

There are a very large number of bee species. In the UK alone there are 270 species, 250 of which are solitary.

There’s a clue.

Solitary bees are like me at a disco … they have no one to dance with 🙁

I’ll cut to the chase to help you erase that vision.

The only bees that use the waggle dance are honey bees. These all belong to the genus Apis.

They include our honey bee, the western honey bee (Apis mellifera), together with a further seven species:

  1. Black dwarf honey bee (Apis andreniformis)
  2. Red dwarf honey bee (Apis florea)
  3. Giant honey bee (Apis dorsata)
  4. Himalayan giant honey bee (Apis laboriosa
  5. Eastern honey bee (Apis cerana)
  6. Koschevnikov’s honey bee (Apis koschevnikovi)
  7. Philippine honey bee (Apis nigrocincta)

Dancing and evolution

Dwarf honey bees nest in the open on a branch and dance on the horizontal surface of the nest. The waggle run is orientated ‘towards’ the food source. Apis dorsata is also an open-nesting bee, but forms large vertically-hanging combs. It dances relative to gravity, and indicates the direction by the angle of the waggle run in the same way that A. mellifera does.

The cavity nesting bees, A. cerana, A. mellifera, A. koschevnikovi, and A. nigrocinta produce the most developed form of the dance.

The dances of A. mellifera and A. cerana are sufficiently similar that they can follow and decode the dance of the other.

The complexity of the nest site and the waggle dance reflects the evolution of these bee species. The earliest to evolve (i.e. the most primitive), A. andreniformis and florea, have the simplest nests and the most basic waggle dance. In contrast, the cavity nesting species evolved most recently, form the most complex brood nests and have the most derived waggle dance.

When and why did the waggle dance evolve?

Assuming that the waggle dance did not independently evolve (there’s no evidence it did, and ample evidence due to its similarity between species that it evolved only once) it must have first appeared at least 20 million years ago, when extant honey bee species diverged during the early Miocene.

The ‘why’ it evolved is a bit more difficult to address.

Behavioural changes often arise in response to the environment in which a species evolves.

Bipedalism in non-human primates (like the australopithecines) is hypothesised to have evolved in part due to a reduction in forest cover and the increase in savannah. Apes had to walk further between clumps of trees and bipedalism offered greater travel efficiency.

Perhaps the waggle dance evolved to exploit a particular type or distribution of food reserves?

In this regard it is interesting that the ‘benefit’ of waggle dance communication varies through the season.

If you turn a hive on its side the combs are horizontal 8. Under these conditions the dancing bees can communicate the presence and quality of a food source. However, they cannot communicate its location (either direction or distance).

No directional or distance information is now available

In landmark studies Sherman and Visscher 9 showed that, at certain periods during the season, the absence of this positional information did not affect the weight gain by the hive i.e. the foraging efficiency of the colony.

They concluded that during these periods forage must be sufficiently abundant that simply stimulating foraging was sufficient. Remember those alkanes and alkenes produced by dancing bees that do exactly that?

Tropical habitats

This observation, and some elegant experimental and modelling studies, suggest that dancing is beneficial when food resources are: 

  • sparsely distributed – therefore difficult (and energetically unfavourable) to find by individual scouting
  • clustered or short-lived resources – when it’s gone, it’s gone
  • distributed with high species richness – if there’s a huge range of flowers, which are the most energetically rewarding (sugar-rich) to collect nectar from?

One of the experimental studies that contributed to these conclusions (though there’s still controversy in this area) was the demonstration that waggle dancing was beneficial in a tropical habitat, but not in two temperate habitats. This makes sense, as food resources have different spatiotemporal distribution in these habitats. Tropical habitats are characterised by clustered and short-lived resources.

Therefore the suggestion is that the waggle dance of Apis species evolved, presumable early in the speciation of the genus, in a tropical region where food resources were patchily distributed, available for only limited period and present alongside a wide variety of other (less good) choices.

For example, like individual trees flowering in a forest …

Finally, it’s worth noting that there is evidence that bees that dance are able to successfully exploit food resources further away than would otherwise be expected from their body size.

This also makes sense.

It’s much less risky flying off over the horizon if you know there’s something to collect once you get there 10.


Notes

If you arrived here from my Twitter feed (@The_Apiarist) you’ll have seen the tweet started with the words “Dance like nobody’s watching”, words that are often attributed to Mark Twain. 

The full quote is something like “Dance like nobody’s watching; love like you’ve never been hurt. Sing like nobody’s listening; live like it’s heaven on earth”.

Pretty sound advice.

But it’s not by Mark Twain. It’s actually from a country music song by Susanna Clark and Richard Leigh. This was first released on the Don Williams album Traces in 1987. So only about 90 years out 😉 

OA Q&A

The post last week on the preparation of oxalic acid (OA; the active ingredient in the commercially available and VMD approved product Api-Bioxal) generated a slew questions. Inevitably, some of these drifted off topic … at least as far as the specific content of the post was concerned.

This partly reflects the deficiency of a weekly blog as a means of communicating.

It may also reflect the inadequacy of the indexing system 1.

Comprehensive coverage of subject, and peripherally related topics, would require a post so long that most readers 2 would give up halfway through.

And it would take so long to write that the weekly post format would have to be abandoned.

The resulting magnum opus would be a masterpiece of bad punctuation, littered with poor puns and would leave me nothing to write the following week …

This week I’ve attempted to address a series of oxalic acid-related points that should have been mentioned before, that I’ve received questions about, or I think justify a question (and answer).

Should I trickle treat or vaporise?

One of the key features of approved miticides is that, used according to the instructions and at the appropriate time, they are very effective.

Conversely, use them incorrectly or at the wrong time and they will be, at best, pretty hopeless.

In the case of OA, both trickle treating (dribbling) or vaporisation (sublimation) can achieve 90% or more reduction in the levels of phoretic mites.

Therefore, the choice between them is not on the grounds of efficacy but should be on their ease of us, convenience, safety or other factors.

Trickle treating is fast, requires a minimum amount of specialised equipment and only limited PPE (personal protection equipment).

I’d strongly recommend using a Trickle 2 bottle from Thorne’s to administer the solution. It is infinitely better than a syringe, which requires the use of at least two hands.

If you hold the crownboard up at an angle with one hand you can administer the OA solution using the other. Wear gloves and your bee suit. It takes as long to read as it does to do.

With a Trickle 2 bottle and some pre-warmed OA-containing solution it should be possible to open, treat and close a colony in well under two minutes. Like this …

On a cold day very few bees will be disturbed. The OA will dribble down through the clustered colony and the mites will get what they deserve 🙂

Temperature and treatment choice

It’s usually the temperature that determines whether I trickle or vaporise. I prefer to trickle when the colony is clustered, but would usually treat by sublimation on a warmer day.

At what temperature does cold become warm? About 8-9°C … i.e. about the temperature at which the bees start to cluster.

Partly this is to reduce the number of bees that might be disturbed – I can vaporise a colony without opening the box.

However, my crashingly unscientific opinion – based entirely on gut feeling and guesswork 3 – is that the OA vapour perfuses through loose clusters  better, whereas the solution is more likely to come into contact with the mites when dribbling down through the cluster.

I have no data to support this – don’t say you weren’t warned!

Through choice I’d not treat (unless I had to) if the temperature was much below 3-4°C. The bees get rapidly chilled should something goes wrong – you drop the bottle, get a bee in your veil or whatever.

Single use ...

Caramel coated Sublimox vaporiser pan

Of course, if you haven’t got a vaporiser your choice is limited to trickle treating. Likewise, if you don’t enjoy scouring caramelised glucose from the pan of your vaporiser you should probably stick to trickling Api-Bioxal solution.

The only additional thing to consider is whether there’s brood present in the hive – I discuss this in more detail below.

How can I use a vaporiser and an Abelo poly floor?

I use a lot of Abelo poly hives. Mine are all the ‘old design‘ with the floor that features a long landing board and an ill-fitting Varroa tray. The new ones don’t look fundamentally different from the website 4.

Abelo poly National hives ...

Abelo poly National hives …

My storage shed has a shoulder-high stack of unused Abelo floors as I prefer my own homemade ‘kewl’ floors.

However, inevitably some Abelo floors get pressed into use during the season and – through idleness, disorganisation and a global virus pandemic – remain in use during the winter 🙁

I’ve now worked out how to vaporise colonies using these floors. Please remember, my vaporiser is a Sublimox which has a brass (?) nozzle through which the vapour is expelled. The nozzle gets very hot and melts polystyrene.

Don’t ask me how I know 🙁

The underside of the open mesh floor can be sealed by inverting the Varroa tray and wedging a block of foam underneath at the back. I didn’t think this would work until I tried it, and was pleasantly impressed.

Abelo poly floor set up for OA vaporisation

This is important as it significantly reduces the loss of OA vapour. Any vapour that escapes is OA that will not be killing mites.

The Sublimox can be simultaneously inserted and inverted through the front entrance. This takes some deft ‘wrist action’ but results in minimal loss of OA vapour.

To protect the poly I use a piece of cardboard. You simply rest the nozzle on this.

As soon as the vaporiser is removed the bees will start to come out, so use the cardboard to block the entrance for a few minutes, by which time they will have settled.

No expense spared cardboard ‘protector’ for poly floor

The gaffer tape in the photo above is sealing the ventilation holes in the entrance block, again keeping valuable OA vapour inside the hive.

And on a related point …

My favoured nuc is the Everynuc. This is a Langstroth-sized box with a removable floor and an integral feeder that more-or-less converts the box to take National frames. It’s well-insulated, robust, easy to paint and – in my view – a more flexible design that the all-in-one single moulded boxes (like the offering from Maisemores).

However, the entrance of the Everynuc is too big.

Everynuc entrance

Open wide …

The disadvantage of this is that a DIY entrance reducer is needed if the nuc is weak and at risk from robbing.

Conversely, the large entrance and short (~2cm) “landing board” is preferable during OA vaporisation. I carry a nuc-width strip of wood, 2 cm thick, with a central 7 mm hole.

With this balanced on the landing board, the vaporiser can be inserted and inverted without loss of vapour or risk of melting the poly. It’s a quick and dirty fix that I discovered several years ago and have never got round to improving.

How do I know if the colony is broodless?

Oxalic acid is a single-use treatment, remaining active in the hive for significantly less time than a brood cycle (see mite counts below). Therefore, the ‘appropriate time’ to use it is when the colony is broodless.

An additional consideration is that open brood is very sensitive and responds unfavourably to a warm acid bath in OA i.e. it dies 5.

In contrast, sealed brood is impervious to OA vapour or solution.

So, how can you tell if the colony is broodless or not?

The easiest way to determine whether the colony has sealed brood is – on a slightly better day – to open the box and have a look.

Done quickly and calmly I suspect this is more distressing for the beekeeper than it is for the colony. You think the bees will be aggressive or distressed. In reality they’re usually pretty lethargic and often very few fly at all.

You only need to look at the frame in the centre of the cluster. If there’s brood present it will be where the bees are most concentrated. You will probably well see the queen nearby.

Gently, gently, quicky peeky

Remove the roof and insulation and lift one corner of the crownboard. Give them a gentle puff of smoke under the crownboard 6. Wait 30 seconds or so and gently remove the crownboard.

There will be bees on the underside of the crownboard. Stand it carefully to the side out of the breeze. The bees will probably crawl to the upper edge, remember to shake them off into the hive rather than crush them when you place it back on the hive.

The colony is likely to be clustered if the weather is 8°C or cooler. Remove the outer frame furthest from the cluster. If it’s late autumn or early winter this should still be heavy with stores. Here’s one I pulled out last week.

Outer frame from a colony in early winter

Now you have space to work. Viewed from above the cluster will often be spread over several frames and shaped approximately like a rugby ball.

In the hive shown above they occupied the front five seams 7 with a few stragglers between frames 6 and 7.

Early winter cluster

I used my hive tool between frames 3 and 4 to split the colony, just levering them a centimetre or so apart, so I could then separate frame 3 from 2 and lift it out.

The queen was on the far side of frame 3.

It looks like magic to inexperienced beekeepers, but it really isn’t …

The top of the frame was filled with sealed stores, the lower part of the frame was almost full of uncapped stores.

There was no sealed brood and no eggs or larvae that I could see 8. An adjacent hive looked very similar. Again, the queen was on the reverse side of the first frame I checked. The bees were barely disturbed. Almost none flew and the boxes were carefully sealed up again.

No brood, so ready to treat 🙂

Can I determine if there’s brood present without opening the hive?

Possibly.

You should be able to tell if brood is emerging by the appearance of the characteristic biscuit-coloured wax crumbs on the Varroa tray.

Think digestive rather than Fox’s Party Rings

Not this colour of biscuit

To see this evidence you need to start with a clean Varroa tray. In addition, the underside of the open mesh floor must be sufficiently draught-free that the cappings aren’t blown around, or accessible to slugs.

Cleaned Varroa tray

Remember that there might be only a very small amount of brood emerging. They may also be uncapping stores (which will have much paler cappings).

Leave the tray in place for a few days and check for darker stripes of crumbs/cappings under the centre of the cluster.

Biscuit-coloured cappings on Varroa tray

Note that the photograph above was taken in mid-February. A late autumn colony would almost certainly have significantly less brood cappings present on the tray. The brood cappings are the two and a bit distinct horizontal stripes concentrated just above centre. The stores cappings are the white crumbs forming the just discernible stripes the full width of the tray.

You cannot use this method to infer anything about whether there’s unsealed brood present. At least, not with any certainty. If, in successive weeks, the amount of brood cappings increases there’s almost certainly unsealed brood present. Conversely, if brood cappings are reducing there may not be unsealed brood if the queen is just shutting down.

While you’re staring at the tray …

Look for Varroa.

It’s useful to have an idea of the mite drop in the few days before OA treatment.

If it’s high then treatment is clearly needed.

If it’s low (1-2 per day) you have a useful baseline to compare the number that fall after treatment.

You may well be surprised (or perhaps disappointed) at the number that appear from a colony that has already had an autumn treatment.

It’s worth remembering that 9 there will be more mites present in the winter if you treated early enough in the autumn to protect the winter bees (blue line).

Mite numbers after early and late autumn treatment

Conversely, if you get little or no mite drop with an OA treatment in the winter it indicates the  bees have not been rearing brood in the intervening period. That means the diutinus winter bees were reared before or during the last treatment, meaning they will have been exposed to high mite levels (red line).

This is not a good thing™.

In my experience the daily mite drop is highest 24-48 hours after treatment. I usually try and monitor it over 5-7 days by which time the drop has reached a basal level, presumably because the OA has disappeared or stopped being effective.

Finally, the ambient temperature has an influence on the Varroa drop. I’ll write about this sometime in the future, but it’s worth looking out for.


 

Oxalic acid (Api Bioxal) preparation

This post updates and replaces one published three years ago (which has now been archived). The registered readership of this site has increased >200% since then and so it will be new to the majority of visitors.

It’s also particularly timely.

I will be treating my own colonies with oxalic acid in the next week or so.

Mites and viruses

Varroa levels in the hive must be controlled for successful overwintering of colonies. If you do not control the mites – and by ‘control’ I mean slaughter 😉 – the viruses they transmit to the overwintering bees will limit the chances of the colony surviving.

The most important virus transmitted by Varroa is deformed wing virus (DWV). At high levels, DWV reduces the lifespan of worker bees.

This is irrelevant in late May – there are huge numbers of workers and they’re only going to live for about 6 weeks anyway.

In contrast, reduced longevity is very significant in the winter where more limited numbers of overwintering bees must survive for months to maintain the colony through to the Spring. If these bees die early (e.g. in weeks, not months), the colony will dwindle to a pathetic little cluster and likely freeze to death on a cold winter night.

Game over. You are now an ex-beekeeper 🙁

To protect the overwintering bees you must reduce mite levels in late summer by applying an appropriate miticide. I’ve discussed this at length previously in When to treat? – the most-read post on this site.

I’d argue that the timing of this late summer treatment is the most important decision about Varroa control that a beekeeper has to make.

However, although the time for that decision is now long-gone, there are still important opportunities for mite control in the coming weeks.

In the bleak midwinter

Miticides are not 100% effective. A proportion of the mites will survive this late summer treatment 1. It’s a percentages game, and the maximum percentage you can hope to kill is 90-95%.

If left unchecked, the surviving mites will replicate in the reducing brood reared between October and the beginning of the following year. That means that your colony will potentially contain more mites in January than it did at the end of the late summer treatment.

Mid September

Late summer mite treatment and no midwinter treatment.

Over several years this is a recipe for disaster. The graph above shows modelled data that indicates the consequences of only treating in late summer. Look at the mite levels (in red, right hand vertical axis) that increase year upon year.

The National Bee Unit states that if mite levels exceed 1000 then immediate treatment is needed to protect the colony. In the modelled data above that’s in the second year 2.

In contrast, here is what happens when you also treat in “midwinter” (I’ll discuss what “midwinter” means shortly).

Two optimal treatments

Two optimal treatments

Mite numbers remain below 1000. This is what you are aiming for.

For the moment ignore the specific timing of the treatment – midwinter, late December etc.

Instead concentrate on the principle that determines when the second treatment should be applied.

During the winter the colony is likely to go through a broodless period 3.

When broodless all the mites in the colony must, by definition, be phoretic.

There’s no brood, so any mites in the colony must be riding around on the backs of workers.

A phoretic mite is an easy mite to kill 4.

A “midwinter” double whammy

A single oxalic acid based treatment applied during the winter broodless period is an ideal way to minimise the mite levels before the start of the following season.

Oxalic acid is easy to administer, relatively inexpensive and well-tolerated by the bees.

The combination – a double whammy – of a late summer treatment with an appropriate miticide and a “midwinter” treatment with oxalic acid should be all that is needed to control mites for the entire season.

However, “midwinter” does not mean midwinter, or shouldn’t.

Historically, winter mite treatments were applied between Christmas and New Year. It’s a convenient time of the year, most beekeepers are on holiday and it’s a good excuse to avoid spending the afternoon scoffing mince pies in front of the TV.

Or with the outlaws inlaws 😉

But by that time of year many colonies will have started brooding again.

With sealed brood, mites have somewhere to hide, so the treatment will be less effective than it might otherwise have been 5.

Why go to all the trouble of treating if it’s going to be less effective than it could be?

The key point is not the timing … it’s the broodlessness of the colony.

If the colony is broodless then it’s an appropriate time to treat. My Fife colonies were broodless this year by mid-October. This is earlier than previous seasons where I usually have waited until the first protracted cold period in the winter – typically the last week in November until the first week in December.

If they remain broodless this week I’ll be treating them. There’s nothing to be gained by waiting.

Oxalic acid (OA) treatment options

In the UK there are several approved oxalic acid-containing treatments. The only one I have experience of is Api-Bioxal, so that’s the only one I’ll discuss.

I also give an overview of the historical method of preparing oxalic acid as it has a bearing on the amount of Api-Bioxal used and will help you (and me) understand the maths.

OA can be delivered by vaporisation (sublimation), or by tricking (dribbling) or spraying a solution of the chemical.

I’ve discussed vaporisation before so won’t rehash things again here.

Trickling has a lot to commend it. It is easy to do, very quick 6 and requires almost no specialised equipment, either for delivery or personal protection (safety).

Trickling is what I always recommend for beginners. It’s what I did for years and is a method I still regularly use.

The process for trickling is very straightforward. You simply trickle a specific strength oxalic acid solution in thin syrup over the bees in the hive.

Beekeepers have used oxalic acid for years as a ‘hive cleaner’, as recommended by the BBKA and a range of other official and semi-official organisations. All that changed when Api-Bioxal was licensed for use by the Veterinary Medicines Directorate (VMD).

Oxalic acid and Api-Bioxal, the same but different

Api-Bioxal is the VMD-approved powdered oxalic acid-containing miticide. It is widely available, relatively inexpensive (when compared to other VMD-approved miticides) and very easy to use.

Spot the difference ...

Spot the difference …

It’s very expensive when compared to oxalic acid purchased in bulk.

Both work equally well as both contain exactly the same active ingredient.

Oxalic acid.

Api-Bioxal has other stuff in it (meaning the oxalic acid content is a fraction below 90% by weight) and these additives make it much less suitable for sublimation. I’ll return to these additives in a minute or two. These additives make the maths a bit more tricky when preparing small volumes at the correct concentration – this is the purpose of this post.

How much and how strong?

To trickle or dribble oxalic acid-containing solutions you’ll need to prepare it at home, store it appropriately and administer it correctly.

I’ve dealt with how to administer OA by trickling previously. This is all about preparation and storage.

The how much is easy.

You’ll need 5ml of oxalic acid-containing solution per seam of bees. In cold weather the colony will be reasonably well clustered and its likely there will be a maximum of no more than 8 or 9 seams of bees, even in a very strong colony.

Hold on … what’s a seam of bees?

Three seams of bees

Looking down on the colony from above, a seam of bees is the row visible between the top bars of the frames.

So, for every hive you need 5ml per seam, perhaps 45ml in total … with an extra 10% to cover inevitable spillages. It’s not that expensive, so don’t risk running out.

And the strength?

The recommended concentration to use oxalic acid at in the UK has – for many years – been 3.2% w/v (weight per volume) in 1:1 syrup. This is less concentrated than is recommended in continental Europe (see comments below on Api-Bioxal).

My advice 7 – as it’s the only concentration I’ve used – is to stick to 3.2%.

Calculators at the ready!

The oxalic acid in Api Bioxal is actually oxalic acid dihydrate. Almost all the powdered oxalic acid you can buy is oxalic acid dihydrate.

The molecular formula of oxalic acid is C2H2O4. This has a molecular weight of 90.03. The dihydrated form of oxalic acid has the formula C2H2O4.2H2O 8 which has a molecular weight of 126.07.

Therefore, in one gram of oxalic acid dihydrate powder (NOT Api Bioxal … I’ll get to Api Bioxal in a minute! Have patience Grasshopper) there is:

90.03/126.07 = 0.714 g of oxalic acid.

Therefore, to make up a 3.2% oxalic acid solution in 1:1 syrup you need to use the following recipe, or scale it up as needed.

  • 100 g tap water
  • 100 g white granulated sugar
  • Mix well
  • 7.5 g of oxalic acid dihydrate

The final volume will be 167 ml i.e. sufficient to treat over 30 seams of bees, or between 3 and 4 strong colonies (including the 10% ‘just in case’).

The final concentration is 3.2% w/v oxalic acid

(7.5 * 0.714)/167 * 100 = 3.2% 9.

Check my maths 😉

Recipe to prepare Api-Bioxal solution for trickling

Warning – the recipe on the side of a packet of Api-Bioxal makes up a much stronger solution of oxalic acid than has historically been used in the UK. Stronger isn’t necessarily better. The recipe provided is 35 g Api-Bioxal to 500 ml of 1:1 syrup. By my calculations this recipe makes sufficient solution at a concentration of 4.4% w/v to treat 11 hives. 

There’s an additional complication when preparing an Api-Bioxal solution for trickling. This is because Api-Bioxal contains two additional ingredients – glucose and powdered silica. These cutting agents account for 11.4% of the weight of the Api-Bioxal. The remaining 88.6% is oxalic acid dihydrate.

Using the same logic as above, 1g of Api-Bioxal therefore contains:

(90.03/126.07) * 0.886 = 0.633 g of oxalic acid.

Therefore, to make up 167 ml of a 3.2% Api-Bioxal solution you need to use the following recipe, or scale up/down appropriately:

  • 100 g tap water
  • 100 g white granulated sugar
  • Mix well
  • 8.46 g of Api-Bioxal

Again, check my maths … you need to add (7.5 / 0.886 = 8.46) grams of Api-Bioxal as only 88.6% of the Api-Bioxal is oxalic acid dihydrate.

Scaling up and down

8.46 g is not straightforward to weigh – though see below – and 167 ml may be too much for the number of hives you have. Here’s a handy table showing the amounts of Api-Bioxal to add to 1:1 syrup to make up the amount required.

Api-Bioxal recipes for 3.2% trickling in 1:1 syrup

The Api-Bioxal powder weights shown in bold represent the three packet sizes that can be purchased.

I don’t indicate the amounts of sugar and water to mix to make the syrup up. I’ll leave that as an exercise for the reader … remember that 100 g of sugar and 100 ml of water make 167 ml of 1:1 (w/v) syrup.

Weighing small amounts of Api-Bioxal

The amount of Api-Bioxal used is important. A few grams here or there matter.

If you are making the mix up for a limited number of hives you will have to weigh just a few grams of Api-Bioxal. You cannot do this on standard digital kitchen scales which work in 5 g increments.

Buy a set of these instead.

Digital scales … perfect for Api-Bioxal (and yeast)

These cost about a tenner and are perfect to weigh out small amounts 10 of Api-Bioxal … or yeast for making pizza dough.

A few words of caution

I don’t want to spoil your fun but please remember to take care when handling or using oxalic acid, either as a powder or when made up as a solution.

Oxalic acid is toxic

  • The lethal dose for humans is reported to be between 15 and 30 g. It causes kidney failure due to precipitation of solid calcium oxalate.
  • Clean up spills of powder or solution immediately.
  • Take care not to inhale the powder.
  • Store in a clearly labelled container out of reach of children.
  • Wear gloves.
  • Do not use containers or utensils you use for food preparation. A well rinsed plastic milk bottle, very clearly labelled, is a good way to store the solution prior to use.

Storage

Storage of oxalic acid syrup at ambient temperatures rapidly results in the acid-mediated breakdown of sugars (particularly fructose) to generate hydroxymethylfurfural (HMF). As this happens the colour of the oxalic acid-containing solution darkens significantly.

This breakdown happens whether you use oxalic acid or Api-Bioxal.

Stored OA solution and colour change

Stored OA solution and colour change …

HMF is toxic to honey bees at high concentrations. Studies from ~40 years ago showed that HMF concentrations below 30 mg/l were safe, but above 150 mg/l were toxic 11.

At 15°C HMF levels in OA solution can reach 150 mg/l in a little over a week. At room temperature this happens much faster, with HMF levels exceeding 150 mg/l in only 2-3 days. In the dark HMF levels build up slightly less quickly … but only slightly 12.

Therefore only make up OA solutions when you need them.

If you must store your oxalic acid-containing syrup for any length of time it should be in the fridge (4°C). Under these conditions HMF levels should remain well below toxic levels for at least one year. However, don’t store it for this long … use it and discard the excess.

Or prepare excess and share it with colleagues in your beekeeping association.

Don’t use discoloured oxalic acid solutions as they’ve been stored incorrectly and may well harm your bees.

Another final few words of caution

I assume you don’t have a fridge dedicated to beekeeping? That being the case please ensure that the bottle containing stored oxalic acid is labelled clearly and kept well out of the reach of children.


Notes

A quick trawl through the Veterinary Medicines Directorate database turns up several oxalic acid-containing solutions for managing Varroa. These include:

  • Oxuvar – approved for trickling or spraying, an aqueous solution of oxalic acid to which you add glucose if you intend to use it for trickling.
  • Oxybee – approved for trickling (and possibly other routes, but the paperwork was a minefield!), contains oxalic acid, glycerol and essential oils and is promoted as having a long shelf life.
  • VarroMed – approved for trickling, contains oxalic acid and formic acid and can be used throughout the year in one way or another.

I’ve not read the documentation provided with these and so don’t know the precise concentration of oxalic acid they contain. It will be listed as an active ingredient. I have not used these products. As with everything else on this site, I only write about methods or products I am familiar with. I therefore cannot comment on their relative efficacy compared to Api-Bioxal, to Apivar or to careful siting of your hives in relation to ley lines … or 5G phone masts.

 

Smell the fear

With Halloween just around the corner it seemed appropriate to have a fear-themed post.

How do frightened – or even apprehensive – people respond to bees?

And how do bees respond to them?

Melissophobia is the fear of bees. Like the synonym apiphobia, the word is not in the dictionary 1 but is a straightforward compounding of the Greek μέλισσα or Latin apis (both meaning honey bee) and phobos for fear.

Melissophobia is a real psychiatric diagnosis. Although people who start beekeeping are probably not melissophobic, they are often very apprehensive when they first open a colony.

If things go well this apprehension disappears, immediately or over time as their experience increases.

If things go badly they might develop melissophobia and stop beekeeping altogether.

Even relatively experienced beekeepers may be apprehensive when inspecting a very defensive colony. As I have discussed elsewhere, there are certain times during the season when colonies can become defensive. These include when queenless, during lousy weather or when a strong nectar flow ends.

In addition, some colonies are naturally more defensive than others.

Some could even be considered aggressive, making unprovoked attacks as you approach the hive.

A defensive response is understandable if the colony is being threatened. Evolution over eons will have led to acquisition of appropriate responses to dissuade natural predators such as bears and honey badgers.

I’m always careful (and possibly a little bit apprehensive) when looking closely at a completely unknown colony – such as these hives discovered when walking in the Andalucian hills.

If Carlsberg did apiaries ...

Apiary in Andalucia

How do bees detect things – like beekeepers or bears – that they might need to mount a defensive response against?

Ignore the bear

Bees have four senses; sight, smell, touch and taste. Of these, I’ve briefly discussed sight previously and they clearly don’t touch or taste an approaching bear 2 … so I’ll focus on smell.

Could they use smell to detect the scent of an approaching human or bear that is apprehensive of being stung badly?

Let’s forget the grizzly bear 3 for now. At over 200 kg and standing 2+ metres tall I doubt they’re afraid of anything.

Let’s instead consider the apprehensive beekeeper.

Do bees respond to the smell of a frightened human (beekeeper or civilian)?

This might seem a simple question, but it raises some interesting additional questions.

  • Is there a scent of fear in humans?
  • Can bees detect this smell?
  • Have bees evolved to generate defensive responses to this or similar smells?

If two beekeepers inspect the same colony and one considers them aggressive and the other does not, is that due to the beekeepers ‘smelling’ different?

I don’t know the answers to some of these questions, but it’s an interesting topic to think about the stimuli that bees have evolved to respond to.

The scent of fear

This is the easy bit.

Is there a distinctive scent associated with fear in humans?

The Scream by Edvard Munch (1895 pastel version)

Using some rather unpleasant psychological testing researchers have determined that there is a smell produced in sweat secretions that is associated with fear. Interestingly, the smell alone appears not to be detectable. The female subjects tested 4 were unable to consciously discriminate the smell from a control neutral odour.

However, the ‘fear pheromone’ alone caused changes in facial expression associated with fright and markedly reinforced responses to visual stimuli that induced fear.

Females could respond to the fear pheromone produced by males (and vice versa) and earlier MRI studies (involving significantly less unpleasant experiments) had shown that this smell was alone able to induce changes in the amygdala, the region in the brain associated with emotional processing.

So, there is a scent of fear in humans. We can’t consciously detect it, but that doesn’t make it any less real.

Can bees detect it?

Can bees smell the scent of fear?

This is where things get a lot less certain.

I’m not aware that there have been any studies on whether bees can definitively identify the fear pheromone produced by humans.

To conduct this study in a scientifically-controlled manner you would need to know precisely what the pheromone was. It would then be tested in parallel with one or several irrelevant, neutral or related (but different) compounds. In each instance you would have to identify a response in the bee that indicated the fear pheromone had been detected.

All of which is not possible as we don’t definitely know what the fear pheromone is chemically.

We do know it’s present in the sweat of frightened humans … but that’s about it. This makes the experiment tricky. Comparisons would also have to be made with sweat secretions present in the same 5 human when not frightened.

And what response would you look for? Usually bees are trained to respond in a proboscis extension test. In this a bee extends its proboscis in response to a recognised smell or taste.

But, as none of this has been done, there’s little point in speculating further.

So let’s ask the question the other way round.

Would bees be expected to smell the scent of fear?

Smell is very significant to bees.

They have an extremely sensitive sense of smell, reflected in their ability to detect certain molecules as dilute as one or two parts per trillion. Since many people struggle with visualising what that means it’s like detecting a grain of salt in an Olympic swimming pool 6.

Part of the reason we know that smell is so important to bees is because evolution has provided them with a very large number of odorant receptors.

Odorant receptors are the proteins that detect smells. They bind to chemical molecules from the ‘smell’ and these trigger a cellular response of some kind 7. Different odorant receptors have different specificities, binding and responding to the molecules that are present in one or more odours.

Odorant receptor diversity and sensitivity

Bees have 170 odorant receptors, more than three times the number in fruit flies, and double that in mosquitoes. Smell is clearly very important to bees 8.

This is perhaps not surprising when you consider the role of odours within the hive. These include the queen and brood pheromones and the chemicals used for kin recognition 9.

In addition, bees are able to find and use a very wide range of plants as sources of pollen and nectar and smell is likely to contribute to this in many ways.

Finally, we know that bees can detect and respond to a wide range of other smells. Even those present at very low levels which they may not have been exposed to previously. For example Graham Turnbull and his research team in St Andrews, in collaborative studies with Croatian beekeepers, are training bees to detect landmines 10 from the faintest ‘whiff’ of TNT they produce. This deserves a post of its own.

So, while we don’t know that bees could detect a fear pheromone, there’s a good chance that they should be able to.

Evolution of defensive responses

We’re back to some rather vague arm waving here I’m afraid.

In a rather self-fulfilling manner we don’t know if bees have evolved a defensive response to the fear pheromone of humans as – for reasons elaborated above – we don’t actually know whether they do respond to the fear pheromone.

We could again ask this question in a slightly different way.

Might bees be expected to have evolved a defensive response to the fear pheromone?

Long before we developed the poly nuc or the fiendishly clever Flow Hive, humans have been attracted by honey and have exploited bees to harvest it.

The ancient Egyptians kept bees in managed hives over 5000 years ago.

However, we can be reasonably certain that humans provided suitable nesting sites (which we’d now call bait hives) to attract swarms from wild colonies well before that.

But we’ve exploited bees for tens or hundreds of thousands of years more than that.

The ‘Woman(Man) of Bicorp” honey gathering (c. 8000 BC)

There are examples of Late Stone Age (or Upper Paleolithic c. 50,000 to 10,000 years ago) rock art depicting bees and honey from across the globe, with some of the most famous being in the Altamira (Spain) cave drawings from c. 25,000 years ago.

Survival of the fittest

And the key thing about many of these interactions with honey bees is that they are likely to have been rather one-sided. Honey hunting tends to be destructive and results in the demise of the colony – the tree is felled, the brood nest is ripped apart, the stores (and often the brood) are consumed.

None of this involves carefully caging the queen in advance 🙁

This is a strong selective pressure.

Colonies that responded earlier or more strongly to the smell of an apprehensive approaching hunter gatherer might be spared. These would survive to reproduce (swarm). Literally, the survival of the fittest.

All of this would argue that it might be expected that bees would evolve odorant receptors capable of detecting the fear pheromone of humans.

There’s no fire without smoke

There are (at least) two problems with this reasoning.

The first problem is that humans acquired the ability to use fire. And, as the idiom almost says, there’s no fire without smoke. Humans were regularly using fire 150-200,000 years ago, with further evidence stretching back at least one million years that pre-humans (Homo erectus) used fire.

And, if they were using fire you can be sure they would be using smoke to ‘calm’ the bees millenia before being depicted doing so in Egyptian hieroglyphs ~5,000 years ago.

It seems reasonable to expect that the use of smoke would mask the detection of fear pheromones, in much the same way that it masks the alarm pheromone when you give them a puff from your trusty Dadant.

The other problem is that it might be expected that the Mesolithic honey hunters had probably ‘got the job’ precisely because they weren’t afraid of bees. In extant hunter gatherer communities it’s known that there are specialists that have a particular aptitude for the role. Perhaps these beekeepersrobbers produce little of no fear pheromone in the first place?

What about other primates?

It’s well know that non-human primates (NHP’s), like chimpanzees and bonobo, love honey. They love it so much that they are responsible for an entire research area studying tool use by chimps.

Bonobo ‘fishing’ for termites using a tool (I couldn’t find a suitable one robbing honey)

Perhaps NHP’s produce a fear pheromone similar to that of humans? Since they haven’t learned to use fire (and they are very closely related to humans) bees may have evolved to respond to primate fear pheromone(s), and – by extension – to those of humans.

However, chimpanzees and related primates prefer to steal honey from stingless bees like Meliponula bocandei. The only information I could find suggested they avoided Apis mellifera, or “used longer sticks as tools“.

Perhaps not such a strong selective pressure after all …

More arm waving

A lot of the above is half-baked speculation interspersed with a smattering of evolutionary theory.

Bees clearly respond in different ways to different beekeepers. I’ve watched beekeepers retreat from a defensive colony which – later on the same training day – were beautifully calm when inspected by a different beekeeper.

Trainee beekeepers

Trainee beekeepers

Although this might have been due to differences in the production of fear pheromones, it’s clear that the bees are also using other senses to detect potential threats to the colony.

Look carefully at how outright beginners, intermediate and expert beekeepers move their hands when inspecting a colony.

The tyro goes slow and steady. Everything ‘by the book’. Not calm, but definitely very controlled.

The expert goes a lot faster. However, there’s no banging frames down, there are no sudden movements, the hands move beside the brood box rather than over it. Calm, controlled and confident.

In contrast, although the “knowing just enough to be dangerous” intermediate beekeeper is confident, they are also rushed and a bit clumsy. Hands move back and forwards over the box, movements are rapid, frames are jarred … or dropped. A bee sneaks inside the cuff and stings the unprotected wrist. Ouch!

“That’s an aggressive colony. Better treat it with care.”

You see what I mean about arm waving?

I strongly suspect movement and vibration trigger defensive responses to a much greater extent than the detection of fear pheromones in humans (if they’re detected at all).

Closing thoughts

You’ll sometimes read that bees respond badly to aftershave or perfumes. This makes sense to me only if the scent resembles one that the bees have evolved a defensive response against.

Don’t go dabbing Parfum de honey badger behind your ears before starting the weekly inspection.

Mellivora capensis – the honey badger. Believe me, you’re not worth it.

But why would they react aggressively to an otherwise unknown smell?

After all, they experience millions of different – and largely harmless – smells every day. Bees inhabit an environment that is constantly changing. One more unknown new scent does not immediately indicate danger. There would be an evolutionary cost to generating a defensive response to something that posed no danger.

And a final closing thought for you to dwell on …

Humans have probably been using fire to suppress honey bee colony aggression for hundreds of thousands of years.

Why haven’t bees evolved defensive responses to the smell of smoke? 11

Happy Halloween 🙂


 

Does DWV infect bumble bees?

Covid (the disease) is caused by a virus called SARS-Cov-2. SARS is an abbreviation of severe acute respiratory syndrome and the suffix ‘Cov’ indicates that it’s a coronavirus. The final digit (2) shows that it’s the second of this type of virus that has caused a pandemic. The first was in 2003, and was caused by a virus we now call SARS-Cov-1. That virus had a case fatality rate of 11%, but only infected ~8500 people worldwide. 

SARS-Cov-2 is not a human virus, by which I mean it’s not a virus that has been present in the human population for a long time. It’s actually a virus that most probably originated in bats.

We’re still not sure how SARS-Cov-2 jumped species from bats to humans.

SARS-Cov-1 made the same transition from bats and we do have a pretty good idea how this happened. Before the virus was found in bats it was detected in palm civets and raccoon dogs, both of which are farmed for food and sold in live game markets. Neither animal shows any symptoms when infected with SARS-Cov-1.

Bats were also sold in the same live game markets in Guangdong province in China and it seems likely that the virus either crossed directly from bats to humans, or went via a third species such as the palm civet.

Pathogen spillover

It’s likely that SARS-Cov-2 followed the same route. We are entering a second – likely extended – period of geographic lockdown due to Covid. Since SARS-Cov-2 made its cross-species jump from bats to humans it has infected at least 41 million people and killed over 1.13 million.

Pathogens that jump from one species to another can have catastrophic consequences for the recipient population 1 or, as in the case of palm civets, might cause no harm whatsoever.

The term ‘pathogen spillover’ is often used to describe the event when a pathogen – whether viral, bacterial or a parasite – escapes or spills over from its natural host to another species. 

CSI in the apiary … motive, opportunity, means

To make the species jump a number of criteria must occur. The pathogen has to be present at a high enough level to be infectious in the ‘donor’ species. For convenience, let’s consider this as the motive to jump species 2.

Secondly, the pathogen needs to have an opportunity to jump species. For example, because the donor and ‘recipient’ species share the same habitat or regularly come into contact.

Finally, it has to have the means to replicate in the recipient. If it cannot replicate it can never get established in the recipient population or cause disease.

In fact, this is an oversimplification. It also needs to be transmissible between individuals of the recipient species (or it will never spread in the recipient species).

So what has all this to do with the bumble bees in the title of this post?

Honey bees get a bad press from some scientists and environmentalists. They compete with native solitary and other bees and pollinators for environmental resources – like pollen and nectar. Increasingly, particularly in agricultural areas, these can be in limiting supply at certain times of the season. For examples, because all the hedgerows have been grubbed up and the wildflower meadows obliterated.

In addition, there are a number of studies that have suggested that honey bee viruses have spilled over into other pollinators, in particular bumble bees, and that this pathogen spillover has contributed to the decline in free-living bee populations.

Do honey bee viruses have the motive, opportunity and means to cause disease in bumble bees?

Are honey bee viruses responsible for the decline in bumble bee populations?

Correlation and causation

There are numerous studies showing that the most widespread honey bee virus, deformed wing virus (DWV), can be detected in wild-caught bumble bees.

Let me pose a quick question … does detection mean ‘replication’?

Deformed wing virus “does what it says on the tin” in honey bees. When transmitted by Varroa it causes developmental defects in pupae that appear as wing deformities in newly emerged workers.

DWV symptoms

DWV symptoms

There’s also one study that implicates DWV in directly causing disease in bumble bees.

This influential paper, published 15 years ago, demonstrated that some bumble bees had the characteristic crippled wings seen in symptomatic emerging honey bee workers. The ‘smoking gun’ was that DWV was also detected in these bumble bees.

Exhibit A : Evidence for DWV infection in bumble bees – click image for full legend.

This is the only figure in the paper and there have been no substantive follow-up papers. For some reason they showed ‘symptomatic’ Bombus terrestris (the buff-tailed bumble bee; panel A, left) and PCR detection data for B. pascorum (the common carder bee).

Nevertheless, this association between presence and symptoms was sufficient for the authors to conclude “we demonstrated that DWV is pathogenic to at least two bumble bee species … causing wing deformity similar to clinically DWV-infected honey bees”.

Here’s a second important question … does the detection of DWV in bumble bees demonstrate it is responsible for the symptoms observed? 3

As a virologist interested in the evolution, replication and transmission of viruses – and a beekeeper – this seemed like a worthwhile topic to explore in a bit more detail.

There might be a correlation between the presence of DWV in bumble bees, but does this account for causation of the DWV-like symptoms seen in the bumble bees?

Motive and opportunity

Let’s get these two out of the way quickly (though we’ll return to opportunity in the notes at the end).

Remember, viruses don’t want to do anything. I’m using motive as a hideously contrived reference to whether the pathogen, DWV, is present at high and infectious levels in honey bees.

It is.

Healthy, mite-naive (but reared in a hive with Varroa) workers can carry as little as ~1000 DWV viruses. Similar levels of DWV are also present in hives from Varroa-free regions – at least of the UK 4. In contrast, after parasitisation by Varroa, symptomatic or asymptomatic adult worker honey bees regularly have more that 109 (one trillion) viruses coursing through their little bodies. 

This virus is highly infectious. When injected into honey bees, as few as 10 viruses are sufficient to start a new infection and are replicated several million-fold within 24-48 hours.

Let’s agree that they have the ‘motive’ … to spread to other hosts.

They also have the opportunity, at least in the broadest sense of the word. Honey bees and bumble bees share the same environment. They collect nectar and pollen from the same flower species. They can even regularly be seen visiting the same flower simultaneously. In addition, it’s not unusual to see bumble bees trying to access honey bee hives to steal nectar.

I’d argue that the virus appears to have ample opportunity to move from one species to the other.

Does DWV replicate in bumble bees?

This is an important question. The data figure (‘Exhibit A’) shown above does not answer this question. Their assay simply detects the presence of DWV, with no indication of whether the virus is replicating.

And the reason this is important is really explained in the section on motive and opportunity above. DWV is ubiquitous and present at extraordinarily high levels in many honey bees. It’s present in honey bee faeces. It can be detected on flowers that honey bees have visited, or in pollen collected from those flowers.

DWV is absolutely everywhere.

So, if it is everywhere, there’s a good chance it might simply contaminate things … like bumble bees that look a bit sick for other reasons.

However, if DWV is involved in causing disease in bumble bees then the virus must replicate in bumble bees.

Virus replication – select for full size and legend.

I’ve used this figure before. To be certain that the virus is replicating you need to identify the intermediate replication products (the negative strand RNA shown as red arrows above).

Almost none of the large number of papers that have reported “DWV infected bumble bees” have identified these intermediate replication products.

Many studies didn’t even bother looking for these critical intermediate products.

So we did

There are two ways we could have investigated this. We could have collected large numbers of bumble bees from the fields and screened them in the lab for these replication intermediates. The problem with this approach is that DWV might be very rare in bumble bees, or might be common, but only replicate rarely. The additional problem is that it involves going out and collecting bees from the environment – that’s hard work 😉 5

An alternative approach is to buy a nest of bumble bees 6 and to inject a few bumble bee pupae and adults with DWV. This is what we did. In parallel, to ‘prove’ the virus used can replicate in honey bees, we injected a few honey bee pupae.

We injected the bees as it’s the definitive way we have of being sure that the virus was present.

‘Gene jockeys’

I’ve got some gifted molecular virologists in my lab. These are scientists who use genetic engineering or biotechnology techniques to address tricky questions (gene jockeys). They are particularly skilled at manipulating nucleic acids, such as the genomes of viruses.

If DWV is so common (it is – see above) how would we know that the replication intermediates were from the virus we injected into the bumble bees, rather than from a virus that was possibly already present?

To solve this puzzle Alex (the lead author on our recent paper) did two things. She engineered a unique genetic marker into the virus which we could look for (and that knew was absent from other similar viruses that might already be present in bumble bees). In addition, she ensured that the virus she injected into the bumble bees contained none of the negative strand RNA that is produced as the intermediate when the virus replicates. 

And … to cut a long story short, we could detect the negative strand RNA replication intermediate in injected bumble bees. In addition, the virus contained the unique genetic marker Alex had engineered into the virus genome, so we were absolutely certain it was the injected virus that was replicating. All of the controls worked exactly as expected.

DWV does replicate in bumble bees … at least under the conditions used in our experiment.

But it does not replicate very fast

The bumble bees we used for these experiments are commercially produced under very clean conditions. When we tested control bumble bees they contained no DWV at all, even using our most sensitive assays.

In contrast to injected honey bee pupae, DWV replicates rather slowly in bumble bees. In honey bees it will amplify a million-fold in 48 hours. However, in bumble bees, in 48 hours we only observed a 100-10,000 fold increase in DWV levels. It was only when we injected large amounts of DWV to bumble bees that we could recapitulate the virus levels seen in symptomatic honey bees.

This was a little puzzling as we’ve assumed that the very rapid replication of DWV in honey bees contributes to pathogenesis. The virus needs to replicate fast to spread through the pupa and infect the particular tissues and organs that, when damaged, result in the characteristic symptoms seen.

If it only replicates slowly in bumble bees how can it cause symptoms?

But hold on … does it cause symptoms?

Not as far as we can tell. 

We never found any injected bumble bees with deformed wings, or any that looked anything like the symptoms seen with DWV in honey bees. The actual quote from the paper is:

Strikingly, none of the eclosed bumble bees showed any signs of the wing deformities that are characteristic of DWV infection of honey bees”. 

Morbidity of DWV in bumble bees

Injected pupae developed until eclosion and were either non-viable, discoloured or apparently normal in appearance (see (c) above). We observed similar numbers of these three types whether the pupae were injected with DWV or mock-injected with buffer alone (see (b) above). What’s more, of those injected with the virus, the level of the virus was the same irrespective of the appearance (or viability) of the bumble bee (see (a) above).

We know that these bumble bees contain replicating DWV but see no evidence for overt disease. I acknowledge that they may have invisible symptoms. However, we see no evidence for the wing deformities reported in the 2005 paper from Genersch and colleagues (‘Exhibit A’, above).

Heavy going? But I’ve only just started … 

So, let’s briefly return to our “motive, opportunity, means” crime analogy and summarise where we’ve got to so far. 

DWV is present at very high levels in at least some honey bees. In addition, bumble bees are likely to regularly come into contact with DWV in the environment. This could happen through contaminated pollen, when attempting to rob hives, or by direct interaction with honey bees when both visit flowers. Finally, and most tellingly, DWV replicates in bumble bees.

So, if I was Peter Falk as Lieutenant Columbo, I’d argue that DWV has the motive, opportunity and means to potentially cause disease in bumble bees.

But, as is apparent from the figure above, it appears not to actually cause disease.

Which is puzzling. 

Just one more thing 7

There’s a major problem with the experiments I’ve discussed so far.

Like all experiments 8 they were tightly controlled, with single variables and lots of statistical analysis to demonstrate our confidence in their reproducibility.

The problem wasn’t technical, it was how well they recapitulated potential transmission in the environment.

We’re not aware of anything that goes around “injecting” bumble bee pupae or adults 9. They are not parasitised by Varroa and, although there are bumble bee mites (such as Parasitellus), they don’t feed on bumble bees in the same way that Varroa feeds on honey bees.

How else might bumble bees acquire DWV?

The obvious route is orally, while feeding. 

There are a few issues with feeding bees DWV. The method is simple enough … you add the virus to sugar syrup and they slurp it down. However, you have little control over how much individual bees consume. Do some bees feed directly and other acquire food when fed by other bees (trophallaxis)? It gets rather difficult control.

In addition, we knew from our studies of honey bees that they are far less susceptible to infection per os (by mouth) than by injection. And by far less I mean tens of thousands of fold less susceptible, at least as adults.

Feeding bumble bees DWV

We chose to investigate two routes of feeding.

The first was to directly feed individual bees in the laboratory. Using this approach we failed to detect any evidence for infection or DWV replication in fed adult bumble bees, even when fed 100 million DWV viruses.

Not an encouraging start. However, larvae generally have increased susceptibility to pathogens, so we also investigated feeding larvae in the laboratory. In these studies we did manage to establish infection. However, to do so we had to add 100 million DWV viruses to he food and only achieved a 50% infection rate. 

The second approach we used was direct feeding of complete bumble bee colonies maintained in the lab.

Bumble bees are easier to keep in the lab than honey bees as they don’t need to be free-flying. Each colony occupies a 30cm3 perforated plastic box, supplied with pollen and syrup. We fed three colonies 100 million DWV per bee per day for 4-6 weeks 10.

That’s a huge amount of virus for a protracted period. Our reasoning here was straightforward. Perhaps there was a particular developmental stage that had increased susceptibility? Perhaps adult bees feeding larvae would – for whatever reason – reduce their resistance to infection via the oral route?

We screened every egg, larva, pupa and adult bee for replicating DWV at the end of the experiment.

There was none present 🙁 ( or perhaps 🙂 , depending upon your viewpoint )

Summary and conclusions

We generated unequivocal evidence that DWV replicates in bumble bees. Specifically in Bombus terrestris, the buff tailed bumble bee. I’d be surprised if it did not replicate in other Bombus species, but that will need to be investigated. 

Infection of adult bees was only possible by injection, with no evidence for infection during feeding.

Bumble bee larvae can be infected with DWV while feeding, but only when fed very large amounts of virus directly. When larvae were reared by a colony supplied with DWV-laced food for several weeks the larvae did not become infected.

These results were recently published in Scientific Reports (Gusachenko et al., 2020) and are freely available. The title of the paper neatly sums up the study “Evidence for and against deformed wing virus spillover from honey bees to bumble bees: a reverse genetic analysis”

What does this mean in terms of our understanding of pathogen spillover from managed honey bee colonies to free living bees? 

If ecologists and environmental scientists are going to make the case that honey bees are threatening the survival of free-living solitary or bumble bees (due to pathogen spillover) they need to:

  1. formally demonstrate that the honey bee virus replicates in the free-living bee
  2. show that this replication is detrimental to the free-living bee
  3. provide evidence for a natural route of transmission by which infection can occur

In my view, and using legal terms again, it’s case proven for the first point in Bombus terrestris 11. In contrast, if I was the judge I’d throw out the other cases due to lack of evidence.

Monkey puzzles

There are viruses everywhere. Every living species has one or more viruses that infect it. Inevitably, because viruses replicate to very high levels, species other than the natural host may become exposed.

But almost always this has no consequences at all …

And to illustrate that I’ll briefly describe a study of monkey viruses infecting humans in Cameroon from several years ago. HIV is one of a very large group of viruses called immunodeficiency viruses. The ‘H’ stands for human, though the virus originated in chimpanzees and is very closely related to the simian immunodeficiency viruses (SIV).

A study of hunters living in the forests of Cameroon showed evidence for exposure to multiple different SIV isolates in tribespeople who hunted non-human primates or who were involved in butchering them or preparing them for market or cooking. There was no evidence these viruses were spreading in the human population, or that there was any sickness or disease associated with prior exposure. 

Environmental exposure happens all the time, and is relatively easy to detect. That’s exactly what had happened with these monkey viruses.

But evidence for environmental exposure, whilst easy to get, is not sufficient to support a claim that the virus causes disease at the level of the individual, or that it threatens an entire population.

As a virologist I think it’s interesting that DWV replicates in Bombus terrestris. However, I’ve yet to see any convincing evidence that DWV spillover from honey bees is responsible for the decline in wild bee populations.

Circumstantial evidence is not the same as convincing evidence.


Notes

What are the missing experiments that we didn’t do?

A key one is to determine whether long-term infection of bumble bees with DWV results in disease. We didn’t see overt deformed wing disease, but it’s possible that infection for weeks could have caused this or other symptoms. 

Although we fed bumble bee nests for weeks with DWV we saw no evidence of larval infection. This was despite previously demonstrating that larvae could be infected with high levels of DWV orally. One possibility is that DWV is inactivated by adult bees. I think it would be interesting to look at the level of infectious DWV in larval food.

Are there natural routes of exposure to DWV that result in bumble bee infection?

Does DWV ever cause environmental contamination at a high enough level to naturally infect bumble bees? For example, is the level of DWV in honey bee faeces high enough and does it ever contaminate pollen?

We are not going to do these studies so it will be interesting to see if others do … or whether simply the presence of the virus (whether replicating or not) will be proof’ that honey bee viruses are responsible for the decline in free-living bee populations.

Diutinus bees

Diutinus is Latin for long-lasting.

Diutinus bees are therefore long-lasting bees. These are the bees that, in temperate regions, maintain the colony through the winter to the warmer days of spring.

I’ve discussed the importance of these bees recently., and I’ve regularly made the case that protecting these ‘long-lived’ bees from the ravages of Varroa-vectored viruses is critical to reduce overwintering colony losses.

Winter is coming …

In most cases the adjective diutinus is replaced with ‘winter’, as in winter bees; it’s a more familiar term and emphasises the time of year these bees are present in the hive. I’ll generally use the terms interchangeably in this post.

Diutinus does not mean winter

From a scientific standpoint, the key feature of these bees is that they can live for up to 8 months, in contrast to the ~30 days a worker bee lives in spring or summer. If you are interested in what induces the production of long-lived bees and the fate of these bees, then the important feature is their longevity … not the season.

Furthermore, a proper understanding of the environmental triggers that induce the production of long-lived bees might mean they could be produced at other times of the season … a point with no obvious practical beekeeping relevance, but one we’ll return to in passing.

It’s worth emphasising that diutinus bees are genetically similar to the spring/summer bees (which for convenience I’ll refer to as ‘summer bees’ for the rest of the post). Despite this similarity, they have unique physiological features that contribute to their ability to thermoregulate the winter cluster for months and to facilitate spring build-up as the season transitions to spring.

What induces the production of winter bees? Is it a single environmental trigger, or a combination of factors? Does summer bee production stop and winter bee production start? What happens at the end of the winter to the winter bees?

Segueing into winter bee production 

The graph below shows the numbers of bees of a particular age present in the hive between the end of August and early December.

Colony age structure from August to December – see text for details

Each distinct colour represents bees reared in a particular 12 day ‘window’. All bees present before the 31st of August are blue. The next 12 day cohort of bees are yellow etc. The area occupied by each colour indicates the number of bees of a particular age cohort.

Note that egg laying (black) is negligible between early October and late November when it restarts.

The graph shows that that there is no abrupt change from production of summer bees to production of winter bees.

For example, about 95% of the blue bees have disappeared by December 1. Of the yellow bees, which first appeared in mid-September, about 33% are present in December. Finally, the majority of the lime coloured bees, that first put in an appearance in early October, are present at the end of December.

The colony does not abruptly stop producing short-lived summer bees on a particular date and switch to generating long-lived ‘diutinus’ winter bees. Instead, as late summer segues into early autumn, fewer short lived bees and more long lived bees are produced. 

Note that each cohort emerge from eggs laid 24 days earlier. The orange cohort emerging from 24/09 to 05/10 were laid within the first two weeks of September. This emphasises the need to treat early to reduce mite levels sufficiently to protect the winter bees.

Winter bees are like nurse bees but different

Before we consider what triggers the production of diutinus bees we need to discuss how they differ from summer bees, both nurses and foragers.

Other than being long-lived what are their characteristics?

Interaction of key physiological factors in nurse (green), forager (red) and winter bees (blue). Colored disks indicate the relative abundance of each factor.

The four key physiological factors to be considered are the levels of juvenile hormone (JH), vitellogenin (Vg) and hemolymph proteins and the size of the hypopharyngeal gland (HPG).

As summer nurse bees transition to foragers the levels of JH increases and Vg decreases. This forms a negative feedback loop; as Vg levels decrease, JH levels increase. Nurse bees have high levels of hemolymph proteins and large HPG, the latter is involved in the production of brood food fed to larvae.

So if that describes the summer nurse bees and foragers, what about the winter bees?

Winter bees resemble nurse bees in having low JH levels, high levels of VG and hemolymph proteins and large HPG’s. 

Winter bees differ from nurse bees in being long lived. A nurse bee will mature into a forager after ~3 weeks. A winter bee will stay in a physiologically similar state for months.

There have also been time course studies of JH and Vg levels through the winter. In these, JH levels decrease rapidly through October and November and are at a minimum in mid-January, before rising steeply in February and March.

As JH levels rise, levels of Vg and hemolymph proteins decrease and the size of the HPG decreases i.e. as winter changes to early spring winter bees transition to foragers.

Now we know what to look for (JH, Vg levels etc) we can return to think about the environmental triggers that cause these changes.

No single trigger

In temperate regions what distinguishes winter from autumn or spring? 

Temperatures are lower in winter.

Daylength (photoperiod) is shorter in winter.

There is less pollen and nectar (forage) available in winter.

Under experimental conditions it’s quite difficult to change one of these variables without altering others. For example, shifting a colony to a cold room (i.e. lowering the ambient temperature to <10°C) leads to a rapid decrease in JH levels (more winter bee-like). However, the cold room was dark, so perhaps it was daylength that induced the change? Alternatively, a secondary consequence of moving the colony is that external forage was no longer available, which could account for the changes observed.

And forage availability will, inevitably, influence brood rearing.

Tricky.

Reducing photoperiod alone does induce some winter bee-like characteristics, such as increases in the protein and lipid content of the fat bodies. It also increases resistance to cold and starvation. It can even cause clustering at elevated (~19°C) temperatures. However, critically, a reduced photoperiod alone does not appear to make the bees long lived. 

Remember also that a reduced photoperiod will limit foraging, so reducing the nutritional status of the colony. This is not insignificant; pollen trapping 2 in the autumn accelerates the production of winter bees.

But again, this may be an indirect effect. Reduced pollen input will lead to a reduction in brood rearing. Feeding pollen to broodless winter colonies induces egg-laying by the queen.

Brood, brood pheromones and ethyl oleate

One of the strongest clues about what factor(s) induces winter bee production comes from studies of free-flying summer colonies from which the brood is removed. In these, the workers rapidly change to physiologically resemble winter bees 3.

How does the presence of brood prevent the generation of diutinus bees?

There are some studies which demonstrate that the micro-climate generated in the colony by the presence of brood – elevated temperature (35°C) and 1.5% CO2 – can influence JH levels. 

However, brood also produces pheromones – imaginately termed brood pheromone – which does all sorts of things in the colony. I’ve discussed brood pheromone previously in the context of laying workers. The brood pheromone inhibits egg laying by worker bees.

Brood pheromone also contributes to a enhancement loop; it induces foraging which results in increased brood rearing and, consequently, the production of more brood pheromone.

One way brood pheromone induces foraging is by speeding the maturation of middle-aged hive bees into foragers. Conversely, when raised in the absence of brood, bees have higher Vg levels, start foraging later and live longer.

But it’s not only brood that produces pheromones.

Workers also produce ethyl oleate, a pheromone that slows the maturation of nurse bees, so reducing their transition to foragers.

A picture is worth a thousand words

All of the above is quite complicated.

Individual factors, both environmental and in the hive, have direct and indirect effects. Experimentally it is difficult to disentangle these. However, Christina Grozinger and colleagues have produced a model which encapsulates much of the above and suggests how the production of winter bees is regulated. 

Proposed model for regulation of production of winter bees.

During autumn there is a reduction in forage available coupled with a reduced daylength and lower environmental temperatures. Consequently, there is less foraging by the colony. 

Since more foragers are present within the hive, the nurse bees are exposed to higher levels of ethyl oleate, so slowing their maturation.

There’s less pollen being brought into the colony (reduced nutrition), so brood production decreases and so does the level of brood pheromone. The reduced levels of brood pheromone also reduces nurse bee maturation.

As shown in the diagram, all of these events are in a feedback loop. The reduction in levels of brood pheromone further reduces the level of foraging … meaning more foragers are ‘at home’, so increasing the effects of ethyl oleate.

All of these events have the effect of retarding worker bee maturation. The workers remain as ‘nurse-like’ long-lived winter bees.

Is that all?

The difference between nurse bees and winter bees is their longevity … or is it?

In the description above, and in most of the experiments conducted to date, the key markers of the levels of JH, Vg and hemolymph proteins, and the size of the HPG, are what has been studied. 

I’d be astounded if there are not many additional changes. 

Comparison of workers and queen bees have shown a large range of epigenetic changes induced by the differences in the diet of young larvae 4. Epigenetic changes are modifications to the genetic material that change gene expression.

I would not be surprised if there were epigenetic changes in winter bees, perhaps induced by alteration of the protein content of their diet as larvae, that influence gene expression and subsequent longevity. Two recent papers suggest that this may indeed happen; the expression of the DNA methyltransferases (the enzymes that cause the epigenetic modifications) differs depending upon the demography of the colony 5 and there are epigenetic changes between the HPG in winter bees and bees in spring 6.

Clearly there is a lot more work required to fully understand the characteristics of winter bees and how they are determined.

Don’t forget …

It’s worth emphasising that the local environment (forage and weather in particular) and the strain of the bees 7 will have an influence on the timing of winter bee production.

Last week I discussed a colony in my bee shed that had very little brood on the 2nd of October (less than one side of one frame). When I checked the colonies last weekend (11th) there were almost no bees flying and no pollen coming in. A colleague checked an adjacent colony on Monday (13th) and reported it was completely broodless. These bees are ‘local mongrels’, selected over several years to suit my beekeeping.

Early autumn colonies

In contrast, my colonies on the west coast are still busy. These are native black bees. On the 14th they were still collecting pollen and were still rearing brood. 

The calendar dates in the second figure (above) are therefore largely irrelevant.

The transition from summer bees to the diutinus winter bees will be happening in your colonies, sooner or later. I suspect it’s already completed in my Fife bees.

Whether genetics or environment has a greater influence on winter bee production remains to be determined. However, I have previously described the good evidence that local bees are better adapted to overwintering colony survival.

To me, this suggests that the two are inextricably linked; locally selected bees are better able to exploit the environment in a timely manner to ensure the colony has the winter bees needed to get the colony through to spring.


 

Preparing for winter

The beekeeping season is fast receding into the distance as the first frosts of autumn appear and, finally, the wasp numbers start to diminish. By now colonies should be heavy with stores, either collected by the bees or provided by the beekeeper.

Winter is coming … be prepared

There is relatively little actual beekeeping to be done this late in the year.

Colonies do not need to be disturbed unnecessarily. They certainly don’t require the usual weekly inspection … they’re not going to swarm, you’ve already applied your miticide of choice and fed them with fondant or syrup 1.

Late queen mating

With temperatures during the day in the low to mid-teens (°C) it is still warm enough to open a colony if you need to.

One of the few reasons I’d open a colony in very late September/early October would be to check if a new queen that had emerged at the end of August had successfully mated. If she had, then all is good. She will continue to lay late into the autumn and should produce sufficient winter bees to get the colony through to the following Spring.

When I lived in the Midlands I would regularly get queens successfully mated in early/mid September. It was pretty dependable, and in good years I’d be actively queen rearing through much of August.

Now, back in Scotland, late queen mating is not something I would want to rely on. I’m certain it happens now and again, but only in very exceptional years.

It’s a tough life being a drone in late August … but not for much longer

This year, many of my colonies turfed their drones out a month ago, and queen mating is not going to happen unless there are plenty of drones about.

A quick peek

It takes just minutes to check whether the queen is mated and laying. Although you don’t need to see the queen, it’s worth using just a whiff of smoke so you have the option of searching for her if needed. If you smoke the colony heavily she’ll end up rushing about or buried under a mass of disturbed bees.

Just a whiff …

You will need to remove the feeder (if using syrup) or the queen excluder and fondant block. Place these aside gently and remember that there are likely to be large numbers of bees adhering to the underside, so balance them on the rim of an upturned roof. This is the time you realise the benefit of using framed rigid wire QE when feeding fondant … removing the block on a flexible plastic QE is a right palaver.

The hive should be busy with bees. Gently remove the dummy board and outer frame. This should be full, or in the process of being filled, with stores. There’s no need to shake the bees off. Just stand it aside out of the way.

‘Guesstimate’ the approximate centre of the brood nest, based upon the density of bees in the seams. Gently lever the frames apart a centimetre or so, then release one of the frames adjacent to the gap you’ve created from its neighbours.

Lift the frame and look for sealed brood, open brood and eggs. By knowing the development cycle of workers bees (3E,5L,13P 2) you can determine approximately when the queen started laying 3.

If she started laying …

Snatching victory from the jaws of defeat

… if there are no eggs or larvae by very late September I would assume that the queen had failed to mate.

You need to use your judgement here. If the weather was poor in the first half of September, but excellent since then, it remains a distant possibility that she has only just mated and has yet to start laying.

Look carefully for polished cells where the centre of the broodnest should be.

And cross your fingers.

Polished cells are a sign that the nurse bees are preparing the comb for egg laying. However, in my experience, they do this even if the queen remains unmated, so it is not a reliable sign that all is well.

You therefore need to use your judgement and be realistic.

Miracles do happen, but you can’t depend upon them 4.

If the weather has been consistently poor – windy, low temperatures (for queen mating, which really needs ~18-20°C) or wet – then assume the worst and ‘save’ the colony by uniting it with a nearby strong colony.

A colony without a laying queen in late autumn will not survive the winter in any state that will make it a viable colony the following year 5.

In Scotland, I routinely unite colonies that do not have a laying queen at the end of August. As described in the last couple of weeks, I do my final colony checks with feeding and miticide treatment.

I know the chances of a queen getting successfully mated after that are effectively zero.

Quick uniting – air freshener

If you need to unite two colonies quickly, without the usual week long wait while they gently mingle after stacking them separated by a sheet of newspaper, you can use a few squirts of household air freshener.

  • Open the queenright recipient colony, removing the feeder and carefully placing it aside to avoid crushing bees (see above)
  • Find the unmated/unlaying/uncooperative queen in the broodless box and remove her (permanently I’m afraid)
  • Spray the top of the recipient colony with a a few squirts of air freshener
  • Do the same with the underside of the now queenless broodless colony
  • Stack the latter on top of the recipient colony
  • Add the feeder back, again giving a squirt or two of air freshener at the interface to stop the bees from fighting

The air freshener masks the distinctive pheromone ‘smell’ of the two colonies, allowing the bees to mingle without fighting.

That’s it.

Job done.

Caveat emptor

Like everything else on this site, I only write here from direct experience. I have successfully united quite a few colonies like this, though nothing like the number I’ve united using newspaper 6.

Given time and the choice I’d always use newspaper 7.

But this late in the season you might not have time.

A day after uniting with air freshener you can, if needed, revisit the hive and go through the double brood box to reduce it to a single box for the winter.

Does it matter which air freshener you use?

I have no idea.

I use Glade Citrus Sunny Beat as it was the cheapest I could find at the time I needed it 8.

Securing the queenright overwintering colony

If you consult the COLOSS records for overwintering colony losses they include a small percentage that are lost to ‘natural disasters’. COLOSS record queen failures and things like that separately, and – in an earlier paper – they define natural disasters as:

… rather loosely defined, as the causes can be very different in participating countries, including fire, storm, flooding, vandalism, bears, martens, woodpeckers, falling trees, suffocation from snow and many more.

The small percentage (0.1 – ~5%) lost to natural disasters vary from country to country, and from year to year.

What is notable about several of these natural disasters is that they should be avoidable.

If your colonies are strong and queenright, and if you’ve fed and treated them to give them the best chance of surviving the winter, it makes sense to do what you can to avoid these natural disasters.

The hive

I use a combination of polystyrene and cedar hives. Sometimes I even combine the two together in a single hive. The majority of my poly hives are from Abelo or Swienty which, for reasons explained elsewhere, are compatible with all the woodenware I own.

The apiary in winter ...

The apiary in winter …

I see no difference in the overwintering colony success between poly and cedar hives.

This doesn’t mean there isn’t one.

I’ve only run about 20 colonies for the last decade. That’s ~200 overwintered colonies. If there were wildly different survival rates I would have noticed. Since I haven’t noticed it either means there is no difference or there is a subtle difference but my sample size is too low 9.

All my colonies overwinter on open mesh floors, usually with the Varroa tray removed. The hives in the photo above are being monitored for mite drop in early December following oxalic acid treatment.

DIY insulation over a perspex crownboard

In addition, all of my hives have a 50 mm thick block of Kingspan under the roof, integrated into the roof, or integrated into the crownboard. In the bee shed my hives have no roof, and are just capped with a block of Kingspan over the crownboard.

Look, no roof … but insulation present all year round

Make sure the stack of boxes in the hive are stable and secure. If the apiary is exposed, strap everything together securely. A colony might survive a week or two of summer showers with no roof, but will surely perish if exposed for any length of time to cold, wet winter weather.

Apiary security

It is unlikely that you will visit the apiary much in the winter. Once a fortnight is more than enough.

It might therefore be worth considering whether it is sufficiently secure from the attention of unwanted human visitors. Unfortunately, incidents of vandalism occur throughout the season, but a hive kicked over in midwinter has less chance of being detected quickly.

Or of surviving.

Although it should probably be included within the ‘Varmints’ section below, large animals – cows, deer, elk, bear, rhino, kangaroo 10 – might also inadvertently, or deliberately, overturn a hive.

Apiary gate

Safe and secure

Fences, either a couple of strands of barbed wire, an electric fence or a full-blown razor-wire topped security barrier, are usually sufficient to keep large two and four-legged visitors at bay.

COLOSS mention both falling trees and flooding as natural disasters.

Winter storms can and do wreak havoc in some years, though I always associate the summer with storm-toppled trees because they’re in full leaf and therefore offer more resistance. It’s certainly worth looking to see if trees adjacent to your apiary might threaten the hives.

Where did Noah keep his bees? In his Ark hive.

Where did Noah keep his bees? In his Ark hive.

Flooding appears to be on the increase. I have experienced minor flooding in one of my apiaries. None of the hives were threatened, but it made access inconvenient for weeks at a time. Again, it’s worth imagining the worst and preparing for it.

Hives often float, but not necessarily the right way up 🙁

Varmints

Having dealt with the threat of large animals 11 it’s also worth considering the damage some small animals can do to hives.

The two main culprits are woodpeckers and mice. Both can be a menace once the frosts set in, but rarely before that.

Woodpeckers, and specifically green woodpeckers (yaffles 12), can learn that beehives contain a wonderful bounty of pupae and larvae. It is learned behaviour. Some green woodpeckers never go near hives, others routinely target them.

In Warwickshire, hives needed to be protected from yaffles. Here in Fife the bird is very much less common and I’ve never had any hives targeted.

Wrapped for winter

Wrapped for winter …

Protection is straightforward. If needed, I simply wrap the hives in a single sheet of DPM (damp proof membrane), pinned in place with drawing pins. The bird need to cling onto the vertical side of the hive to easily burrow through to the brood. The DPM stops them doing this. Leaving bits of the roof or sides of the floor exposed is therefore not a problem 13.

Pixie or Dixie?

Pixie or Dixie?

Mice access hives through overly large entrances. I only have problems with the stupidly cavernous maw of my preferred Everynuc. Mice eat pollen and stores, destroy the brood and wee everywhere 🙁  Thoroughly unpleasant.

Everynuc entrance

Open wide …

A standard mouseguard pinned in place throughout the coldest months of the winter prevents them accessing the hive. Alternatively, on a full-sized colony, the kewl-style underfloor entrances are very effective at excluding rodents.

Kewl open mesh floor showing L-shaped entrance slot

Kewl floor entrance …

That’s not the end of winter-related tasks, but it’s just about all you need to do for your colonies before winter proper starts.

There are some midwinter checks that are needed, but we’ll deal with them nearer the time.


Note

We also have pine martens at one of my apiaries. They are reported to vandalise hives and steal honey (and presumably brood) in late winter. Pine martens are incredibly agile and no fence exists that could keep them out. Time will tell whether they are a problem.

In the meantime, here’s one living up to its name, stealing a pine offcut used to slow down the rate at which they empty the squirrel feeder of peanuts 🙂

Winter bee production

There are big changes going on in your colonies at the moment.

The summer foragers that have been working tirelessly over the last few weeks are slowly but surely being replaced. As they die off – whether from old age or by being eaten by the last of the migrating swallows – they are being replaced by the winter bees.

Between August and late November almost the entire population of bees will have changed. The strong colonies you have now (or should have) will contain a totally different workforce by the end of the year.

Forever young

The winter bees are the ones responsible for getting the colony from mid/late autumn through to the following spring. They are sometimes termed diutinus bees from the Latin for “long lived”.

These are the bees that thermoregulate the winter cluster, protecting the queen, and rearing the small amounts of brood during the cold, dark winter to keep the colony ticking over.

Midwinter cluster

A midwinter colony

Physiologically they share some striking similarities with so-called hive or nurse bees 1 early in the summer.

Both hive bees and winter bees have low levels of juvenile hormone (JH) and active hypopharyngeal glands. Both types of bee also have high levels of vitellogenin, high oxidative stress resistance and corpulent little bodies.

But early summer nurse bees mature over a 2-3 week period. Their JH levels increase and vitellogenin levels decrease. This induces additional physiological changes which results in the nurse bee changing into a forager. They sally forth, collecting nectar, pollen and water …

And about three weeks later they’re worn out and die.

Live fast, die young

And this is where winter bees differ. They don’t age.

Or, more accurately, they age   v  e  r  y    s  l  o  w  l  y.

In the hive, winter bees can live for 6 months if needed. Under laboratory conditions they have been recorded as living for up to 9 months.

They effectively stay, as Bob Dylan mumbled, forever young.

Why are winter bees important?

Although not quite eternal youth … staying forever young is useful as their longevity ensures that the colony does not dwindle and perish in the middle of winter.

With little or no nectar or pollen available in the environment the colony reduces brood rearing, and often stops altogether for a period.

But what about the kilograms of stores and cells filled with pollen in the hive? Why can’t they use that?

Whilst both are present, there’s nothing like enough to maintain the usual rate of brood rearing. If they tried the colony would very quickly starve.

Evolution has a very effective way of selecting against such rash behaviour 🙁

If you doubt this, think how quickly hives get dangerously light during the June gap. With no nectar coming in and thousands of hungry (larval) mouths to feed the colony can easily starve to death during a fortnight of poor weather in June.

The winter bees ‘hold the fort’, protecting the queen and rearing small amounts of brood until the days lengthen and the early season pollen and nectars become available again.

And, just as the winter bees look after the viability of the colony, the beekeeper in turn needs to look after the winter bees … we rely on them to get the colony through to spring.

Lots of bees

Can you identify the winter bees?

But before we discuss that, how do you identify and count the winter bees? How can you tell they are present? After all, as the picture above shows 2, all bees look rather similar …

Counting the long lived winter bees

The physiological changes in winter bees, such as the JH and vitellogenin levels, are only identifiable once you’ve done some rather devastating things to the bee. These have the unfortunate side effect of preventing it completing any further bee-type activities 🙁

Even before you subject them to that, their fat little bodies aren’t really sufficiently different to identify them visually.

But what is different is their longevity.

By definition, the diutinus or winter bees are long lived.

Therefore, if you record the date when the bee emerged you can effectively count back and determine how old it is. If it is more than ~6 weeks old then it’s a winter bee.

Or the queen 😉

And, it should be obvious, if you extrapolate back to the time the first long lived bees appear in the hive you will have determined when the colony starts rearing winter bees.

The obvious way to determine the age of a bee is to mark it upon emergence and keep a record of which marks were used when. Some scientists use numbered dots stuck to the thorax, some use combinations of Humbrol-type paint colours.

I’m not aware that anyone has yet used the barcoding system I discussed recently, though it could be used. The winter bee studies I’m aware of pre-date this type of technology.

Actually, some of these studies date back almost 50 years, though the resulting papers were published much more recently.

This is painstaking and mind-numbingly repetitive work and science owes a debt of gratitude to Floyd Harris who conducted many of the studies.

Colony age structure – autumn to winter

Here is some data showing the age structure of a colony transitioning from late summer into autumn and winter. There’s a lot in this graph so bear with me …

Colony age structure from August to December - see text for details

Colony age structure from August to December – see text for details

The graph shows the numbers and ages of bees in the colony.

The ages of the bees is indicated on the vertical axis – with eggs and brood (the youngest) at the bottom, coloured black and brown respectively. The adult bees can be aged between 1 and ~100 days old 3. The number of bees is indicated by the width of the coloured bar at each of the nine 12 day intervals shown.

All of the adult bees present in the hive at the end of August are coloured blue, irrespective of their age. There are a lot of these bees at the end of August and almost all of them have disappeared (died) by mid-November 4.

The remaining colours indicate all the bee that emerge within a particular 12 day interval. For example, all the bees that emerge between the 31st of August and the 12th of September are coloured yellow.  Going by the width (i.e. the numbers of bees of that age) of the yellow bars it’s clear that half to two-thirds of these bees die by mid October, with the rest just getting older gracefully.

But look at the cohort that emerge between the end of September and early October, coloured like this 5. The number of these bees barely changes between emergence and early December. By this time they are 72 days old i.e. an age that most summer bees never achieve.

Brood breaks and climate

In the colony shown above the queen continued laying reduced numbers of eggs – the black bars – until mid-October and then didn’t start again until the end of November. During this period the average age of the bees in the colony increased from ~36 days to ~72 days and the strength of the colony barely changed.

The figure above comes from a BeeCulture article by Floyd Harris. The original data isn’t directly referenced, but I suspect it comes from studies Harris conducted in the late 70’s in Manitoba, some of which was subsequently published in the Journal of Apicultural Research. In addition, Harris co-authored a paper presenting similar data in a different format in Insectes Sociaux which describes the Manitoban climate as having moderate/hot summers and long, cold winters.

My hives in Scotland, or your hives in Devon, or Denmark or wherever, will experience a different climate 6.

However, if you live in a temperate region the overall pattern will be similar. The summer bees will be replaced during the early autumn by a completely new population of winter bees. These maintain the colony through to the following spring.

The dates will be different and the speed of the transition from one population to the other may differ. The timing of the onset of a brood break is likely to also differ.

However, the population changes will be broadly similar.

And, it should be noted, the dates may differ slightly in Manitoba (and everywhere else) from year to year, depending upon temperature and forage availability.

Colony size and overwintering survival

Regular readers might be thinking back to a couple of posts on colony size and overwintering survival from last year.

One measured colony weight, showing that heavier colonies overwintered better 7. A second discussed the better performance of local bees in a Europe-wide study of overwintering survival. In this, I quoted a key sentence from the discussion:

“colonies of local origin had significantly higher numbers of bees than colonies placed outside their area of origin”

I can’t remember when during the season those studies recorded colony size, but I’m well aware that large colonies in the winter survive better.

The colonies that perish first in the winter are the pathetic grapefruit-sized 8 colonies with ageing queens or high pathogen loads.

In contrast, the medicine ball-sized ‘boomers’ go on and on, emerging from the winter strongly and building up rapidly to exploit the early season nectar.

But what the graph above shows is that the bees in a strong colony in late summer are a completely different population from the bees in the colony in midwinter.

The strength of the midwinter colony is determined entirely by when winter bee rearing starts and the laying rate of the queen, although of course both may be indirectly influenced by summer colony strength.

The influence of the queen

Other than this potential indirect influence, it’s possibly irrelevant how large the summer colony is in terms of winter colony size (and hence survival).

After all, even if the summer bees were three times as numerous, their fate is sealed. They are all going to perish six weeks or so after emergence.

Are there ways that beekeepers can influence the size of the overwinter colony to increase its chances of survival?

I wouldn’t pose the question if the answer wasn’t a resounding yes.

It has been known for a long time 9 that older queens stop laying earlier in the autumn than younger queens. As explained above, the longer the queen lays into the autumn the more winter bees are going to be produced.

Mattila et al., 10 looked at the consequences of late season (post summer honey harvest) requeening of colonies. In these they removed the old queen and replaced her with either a new mated or virgin queen, or allowed the colony to requeen naturally.

Using the ’12 day cohort’ populations explained above, the authors looked at when the majority of the winter bees were produced in the colony, and estimated the overall size of the winter colony.

The influence of new queens on winter bee production.

The influence of new queens on winter bee production. Note shift to the right in B, C and D, with new queens.

With the original old queen, 53% of winter bees were produced in the first two cohorts of winter bees. With the requeened colonies 54-64% of the winter bees were produced on average 36 days later, in the third and fourth cohorts of winter bees.

This indicates that young queens produce winter bees later into the autumn.

This is a good thing™.

In addition, though the results were not statistically significant, there was a trend for colonies headed by new queens to have a larger population of bees overwinter.

Perhaps one reason the requeened colonies weren’t significantly larger was that the new queens delay the onset of winter bee rearing. I’ll return to this at the end.

The influence of deformed wing virus (DWV)

Regular readers will know that this topic has been covered extensively, and possibly exhaustively, elsewhere on this site … so I’ll cut to the chase.

DWV is the most important virus of honey bees. When transmitted by Varroa destructor there is unequivocal evidence that it is associated with overwintering colony losses. The reason DWV causes overwintering losses is that it reduces the longevity of the winter bees.

The virus might also reduce the longevity of summer bees but,

  1. there’s so many of them to start with
  2. there’s loads more emerging every day, and
  3. they only survive a few weeks anyway,

that this is probably irrelevant in terms of colony survival.

Dainat et al., (2012) produced compelling evidence showing that DWV reduces the longevity of winter bees 11. The lifespan was reduced by ~20%.

A consequence of this is that the winter bees die off a little faster and the colony shrinks a little more. At some point it crosses a threshold below which it cannot thermoregulate the cluster properly, further limiting the ability of the colony to rear replacement bees (assuming the queen is able to lay at a low rate).

This colony is doomed.

Even if they stagger through to the longer days of spring they contain too few bees to build up fast. They’re not dead … but they’re hardly flourishing.

Winter bees and practical beekeeping

I think there are three ways in which our understanding of the timing of winter bee production should influence practical beekeeping:

Firstly … The obvious take-home message is that winter bees must be protected from the ravages of DWV. The only way to do this is to minimise the mite population in the colony before the winter bee rearing starts.

The logical way to do this is to treat using an approved miticide as soon as practical after the summer honey is removed 12.

I discuss the importance of the timing of this treatment in When to treat?, which remains one of the most-read posts on this site.

Secondly … Avoid use of miticides (or other colony manipulations) that reduce the laying rate of the queen in early autumn.

When I used to live at lower latitudes I would sometimes use Apiguard. This thymol-containing miticide is very effective if used when the temperature is high enough. However, in my experience a significant proportion of queens stop laying when it is being used. Not all, but certainly more than 50%.

I don’t know why some stop and others don’t. Is it genetic? Temperature-dependent?

Whatever the reason, they stop at exactly the time of the season you want them to be laying strongly.

Thirdly … consider requeening colonies with young queens after the summer honey is removed. This delays the onset of winter bee production and results in the new queen laying later into the year. The later start to winter bee production gives more time for miticides to work.

A win-win situation.


 

Weed and feed

Weed and feed is a generic term that describes the treatment of lawns to simultaneously eradicate certain weeds and strengthen the turf.

It seemed an appropriate title for a post on eradicating mites from colonies and feeding the bees up in preparation for the winter ahead.

Arguably these are the two most important activities of the beekeeping year.

Done properly they ensure you’ll still be a beekeeper next year.

Ignored, or done too little and too late, you’ll join the unacceptably large number of beekeepers who lose their colonies during the winter.

They think it’s all over

In Fife, on the east coast of Scotland, my beekeeping season effectively finishes with the midsummer ‘mixed floral’ nectar sources. This is a real mix of lime, blackberry, clover and Heinz nectars 1 … many of which remain to be identified.

There’s no reliable late nectar flow from himalayan balsam around my apiaries are and not enough rosebay willowherb (fireweed) to be worthwhile, though in a good year the bees continue to collect a bit from both into early September.

But by then the honey supers are off and extracted. Anything the bees find after that they’re welcome to.

The contrast with the west of Scotland is very marked. Over there my bees are still out collecting reasonable amounts of late heather nectar, though the peak of the flow is over.

Storing supers

Once the honey supers are extracted they can be returned to the colonies for the bees to clean up prior to storing them overwinter. However, this involves additional trips to the apiary and usually necessitates using the clearer boards again to leave them bee-free before storage.

I used to do this and quite enjoyed the late evening trips back to the apiary with stacks of honey-scented supers. More recently I’ve stopped bothering and instead now store the supers ‘wet’. The main reasons for this are:

  • laziness lack of time
  • unless you’re careful it can encourage robbing, by wasps or bees. You need to return supers to all the colonies in the apiary and if you have the hives open too long it can induce a frenzy of robbing 2
  • the honey-scented supers encourage the bees to move up faster when they’re used the following season

If you do store the supers ‘wet’ make sure the stacked boxes are bee and wasp-tight. Mine go in a shed with a spare roof on the top. If there are any gaps the wasps, bees or ants will find them and it then becomes very messy. 

I know many beekeepers who wrap their supers in clingfilm. Not the 30 cm wide roll you use in the kitchen but the sort of metre wide swathe they used to wrap suitcases in at London Heathrow.

Dated super frames

The drawn super comb is a really valuable resource and can be used again and again, year after year. I usually record the year a frame was built on the top bar. Many are now over a decade old and have probably accommodated at least 80 lb of honey in their lifetime 3.

The timing of late season Varroa management

During the brood rearing season the Varroa levels in the colony will have been rising inexorably. Without intervention the mites will continue to replicate on developing pupae that would otherwise emerge as the all-important overwintering bees. These are critical to get the colony through to the following spring.

When Varroa feeds on a developing pupa it transmits the viruses – primarily deformed wing virus – it acquired from the last bee is fed on. These viruses amplify by about a million-fold within 24-48 hours. Pupae that do not die before eclosion may have developmental defects. Importantly, those that appear normal have a reduced lifespan.

The overwintering bees should live for months, but might only live for weeks if their virus levels are high.

And if enough overwintering bees have high viral loads and die prematurely, the probability is the the colony will perish in the winter.

You therefore need to reduce mite levels before the overwintering bees are exposed to Varroa

The full details and justification are in a previous post logically entitled When to treat?

TL;DR 4late August to early September is the best time to treat to protect the winter bees from the worst of the ravages of mite-transmitted DWV.

Use an appropriate treatment

You need to reduce the mite levels in the colony by at least 90% to protect the winter bees.

To achieve this you need an appropriate miticide used properly. 

I use Apivar

Apivar is an Amitraz-containing miticide. Although there are reports of mite resistance in some commercial apiaries, the pattern is very localised (individual hives within an apiary, which is difficult to understand) and in my view it is currently the best choice.

What are the alternates?

  • MAQS – active ingredient formic acid – poorly tolerated at high temperatures, but can be used with the supers present
  • Apiguard – active ingredient thymol – ineffective at lower temperatures (it needs an ambient temperature of 15°C to work – that’s not going to happen in Scotland in September).
  • Apistan – active ingredient a synthetic pyrethroid – unsuitable as there is widespread resistance in the mite population.

Using Apivar

Apivar treatment is temperature-independent. It cannot be used when the honey supers are present. You simply hang two strips in the hive for 6 to 10 weeks and let them do their work. The bees tolerate it well and, unlike MAQS or Apiguard, I’ve not seen any detrimental effects on the queen who continues to lay … making more of those important winter bees.

Apivar strips

Each strip consists of an amitraz-impregnated piece of plastic tape with a V-shaped tab that can be pushed into the comb to hold it in place. 

This generally works well as the frames are usually not moved much as there’s no need for inspections this late in the season.

Apivar strip pushed into comb

However, the strips can be a little fiddly to remove (or fall off during frame handling) and some of our research colonies will continue to be used for at least another month. I’ve therefore used a short piece of bent wire to hang the strips from in these hives.

Apivar strip on wire hanger

I place the strips in opposite corners of the hive, set two frames in from the sides. 

Apivar, wax and honey contamination

Although Amitraz is not wax soluble 5 there are recent reports on BEE-L that one of its breakdown products are, including one that has some residual miticide activity 6

I therefore try and get all the bees into the brood box before starting treatment (I described nadiring supers with unripe honey last week).

Very rarely I’ll leave the bees with a super of their own unripe honey. Usually this happens when the brood box is already packed with stores and overflowing with bees. In this case I’ll mark the super and melt down the comb next season rather than risking tainting the honey I produce.

I attended a Q&A session by the Scottish Beekeeping Association last month in which the chief bee inspector discussed finding Apivar strips in honey production hives. He described the testing of honey for evidence of miticide contamination and potential subsequent confiscation.

This is clearly something to be avoided.

Remember to record the batch number of Apivar used and note the date in your hive records. I just photograph the packet for convenience. The date is important as the strips must be removed after 6 weeks and before 10 weeks have elapsed. 

It’s finally worth noting that the instructions recommend scraping the strip with a hive tool part way through the period if they are being used for the full ten week course of treatment. The strips usually get propolised into the frame and the scraping ‘reactivates’ them to ensure that the largest possible number of mites are killed off.

And, after all, that’s what they’re being used for.

Apivar is expensive

Well … yes and no.

Yes it feels expensive when walking out of Thorne’s of Newburgh clutching one small foil packet and being £31 poorer. 

But think about it … that packet is sufficient to treat 5 colonies.

Is £6.20 too much to spend on a colony?

My 340 g jars of honey cost more than £6.20 and my productive colonies produce at least one hundred times that amount of honey. 

I don’t think 1% of the honey value is too much to spend on protecting the colony from mites and the viruses they carry.

Mite drop

Varroa killed by the miticide 7 fall to the bottom of the hive. If you have an open mesh floor (OMF) they fall through … onto the ground or the intervening neatly divided Varroa tray, enabling you to easily count them

Varroa trays ...

Varroa trays …

Remember that amitraz, the active ingredient of Apivar, works by direct contact. This is why you place the strips diametrically opposite one another so that as many bees as possible contact them. Unlike Apiguard, it makes no difference whether the Varroa tray is present or not.

It is useful to ‘count the corpses’ to get an idea of the infestation level and the efficacy of the treatment.

I’m going to discuss what you might expect in terms of mite drop in the winter (I need to plot some graphs first). However, this is something you could think about before then … knowing Apivar kills mites in less than three hours after exposure, what do you think the mite drop should look like over the 6-10 weeks of treatment?

Enough weeding, what about feeding?

I treat and feed colonies on the same day.

I also do the final hive inspection of the season. At this I look for evidence of a laying queen, the general health of the colony, the amount of brood present and the level of stores in the brood box. 

If the colony is queenless (how did that happen without me noticing earlier?) I simply unite the colony with a strong, healthy queenright colony. I don’t bother testing it with a frame of eggs … time is of the essence.

It’s too late to get a queen mated (at least in Fife … when I lived in the Midlands I got a few September queen matings but they could not be relied upon) and I rarely, if ever, buy queens.

I only feed with fondant in the autumn.

Convenience food

I described fondant last week as a convenience food

A spade's a spade ...

A spade’s a spade …

I’ve described in detail many of the benefits of fondant in numerous previous posts. Essentially these can be distilled to the following simple points:

  • zero preparation; no syrup spillages in the kitchen, no marital strife.
  • bucket- and feeder-free; no need to carry large volumes of syrup to the apiary and no feeders to store for the remaining 11 months of the year. All you need to feed fondant is a queen excluder and an empty super … and you’ve got those already.
  • easy to store; unopened it keeps for several years 8.
  • super speedy; I can feed a colony, including cutting the block in half, in less than 2 minutes.
  • good for queen and colony; perhaps that’s stretching it a bit. What I mean is that the bees take the fondant down more slowly than syrup, consequently the queen continues to lay uninterrupted as the brood nest does not get backfilled with stores. This is good for the colony as it means the production of more winter bees.
  • an anti-theft device; you can’t spill fondant so there is much less chance of encouraging robbing by neighbouring bees or wasps.
  • useful boxes; the empty boxes are a good size to store or deliver jarred honey in – each will accommodate sixteen 1 lb rounds.

I’ve fed nothing but fondant for about a decade and can see no downsides to its use.

Money, money, money

I’ve never used anything other than commercially purchased “baker’s” fondant … don’t believe the rubbish (about ‘additives’) some of the bee equipment suppliers use to justify their elevated prices.

You should be paying about £1/kg … any more and you’re being robbed. This year (2020) I paid less than 90p/kg.

Do not use the icing fondant sold by supermarkets for Christmas cakes. I’m sure there’s nothing much wrong with it, but – at £2/kg – you’ll soon go bankrupt. 

Tips for feeding fondant

Fondant blocks are easier to slice in half if they are slightly warm.

Use a sharp bread knife and don’t slice your fingers off. 

You can cut the blocks in half in advance in the warmth of your kitchen and then cover the cut faces with clingfilm to prevent them reannealing, but I just do it in the apiary.

Take care with sharp knives … much easier with a slightly warm block of fondant

Alternatively, use a clean spade 9.

Always place the block cut face down on a queen excluder directly over the top bars of the brood frames. With a full block, it’s like opening a book and laying it face down. Do not place it above a crownboard with a hole in it.

You want the bees to have unfettered access to the open face of the fondant block.

Fondant on queen excluder with eke

Ideally, use a framed wire queen excluder.

These are easier to lift off should you need to go into the colony.

Which you don’t 😉

There’s no need to continue inspections this late into the season. Go and enjoy a week or two away in Portugal … or perhaps not 🙁

If you need to store an unused half block of fondant wrap the cut face in clingfilm.

All my colonies get one full block (12.5 kg) and many get a further half block, depending upon my judgement of the level of the stores in the hive.

Insulation

The bees will take the fondant down over 2 – 4 weeks. They do store it, rather than just using it as needed. By late September or early October all that will remain is the blue plastic husk. The photo below is from mid-October. This colony has had a ‘topup’ additional half block after already storing a full block of fondant.

They fancied that fondant

With cooler days and colder nights, you want to reduce heat loss by the colony and minimise the dead space above the bees into which the heat escapes.

Although bees take fondant down at lower temperatures than they do syrup, there’s no point in giving the colony more additional space to heat than they need.

Poly super and fondant ...

Poly super and fondant …

Depending upon the availability of equipment I do one or a combination of the following:

  • use a poly super to provide space for the fondant
  • compress the fondant (use your boot) into as little space as possible and you squeeze it into a 50 mm deep eke, which (conveniently) is the same depth as the rim on my insulated polcarbonate/perspex crownboards 10.
  • use an eke and an inverted perspex crownboard with no need to compress the fondant
  • add a 50 mm thick block of insulation above the crownboard, under the roof (which may also be insulated)

Fondant block under inverted perspex crownboard – insulation block to be added on top is standing at the side

Oh yes … before I forget … completely ignore any advice you might read on using matchsticks to provide ventilation to the hive 11.

They think it’s all over … it is now

That’s the end of the practical beekeeping for the season 🙁

If your colonies are strong and healthy, if the mite levels are low and they have sufficient stores, there’s almost nothing to do now until March 12

Now really is a good time for a beekeeper to take a holiday.

Make a note in your diary on the date you need to remove the Apivar strips

Write up your notes, pour a large glass of Shiraz and make plans for next season 🙂


 

More gentle beekeeping

I’ve done less beekeeping this year than any time in the past decade. The Covid-19 lockdown enforced changes to the way we live and work, meaning my contact with the bees has been ‘big and infrequent’ rather than ‘little and often’. 

‘Big and infrequent’ meaning a day or three of intense activity every month or so. I’ll write about this once the season is over as it has meant that the season has, in many ways, been very unrewarding … 🙁

… but nevertheless quite successful 🙂

23,000 iced buns

With the season winding to a close, now is the time to remove the supers of summer honey and prepare to feed the colonies for winter. 

Which means a couple of days of very heavy lifting.

I buy fondant in bulk as it stores well until it is needed. This year ‘bulk’ meant over 400 kg which, based upon this recipe, is enough for over 23,000 iced ‘finger’ buns 1. That’s too much to fit in my car (fondant or finger buns 😉 ), so entailed two trips and manhandling the boxes twice – from the pallet to the car and from the car to the shed.

Load 1 of 2 … there’s more in the passenger footwell!

During all that lifting and carrying I focus on the thought that fondant has a lower water content than syrup (~78% sugar vs ~60% for syrup) so I need to feed less weight to get the same amount of sugar into the hive.

And there’s no preparation needed or fancy (expensive) feeders to store for the rest of the year. 

As convenience foods go, it’s very convenient.

But after a dozen or two blocks, also very heavy 🙁

Beekeeper’s back

There’s a bittersweet irony to the honey harvest.

The more backbreakingly exhausting it is, the better it is. 

Not so much there’s no gain without pain” as “the more pain, the more gain”.

I have two main apiaries about 15 miles apart in Fife. I checked the hives in the first apiary and was disappointed to find the supers were mostly empty. This is a site which usually has good summer forage. The OSR had yielded well in the spring, but the colonies had then all had pre-emptive splits for swarm control, before being united back prior to the main flow.

Which appears not to have happened 🙁

I put clearers on the hives and returned the following day to collect a pathetically small number of full supers. There were some uncapped and part-filled frames, some of which contained fresh nectar 2 which I pooled together in the smallest number of supers possible.

I placed these above the floor but underneath the brood boxes.

This is termed nadiring, which isn’t actually a real word according to the OED. Nadir means the lowest point, but in the 17th Century (now obsolete and probably only used by beekeepers) nadir meant a point directly beneath an object.

The hope and expectation here is that the bees will find the stores beneath the cluster and move it up into the brood box, prior to me treating and feeding them up for winter.

Quick fix clearer board – hive side

On the same day I placed clearers underneath the (much heavier) supers in my second apiary. Actually, under about half the hives as I don’t have enough clearers for all the hives at once, even with a few Correx and gaffer tape bodged efforts to supplement them (shown above).

Clearing supers

I’ve discussed these clearers previously. With no moving parts and a deep rim on the underside the bees move down quickly. It’s not unusual to find the full 5cm depth full of bees the following morning.

Lots of bees

These bees have to be gently shaken back into the hive before replacing the crownboard and roof. This is easy on a calm, warm day with placid bees, but can be a little traumatic for everyone concerned if those three key ingredients are missing.

More lifting 🙁

Filled supers usually weigh between 37 and 50 lb (17-23 kg) each 3. Therefore, moving a dozen from the hives to the car and the car to the honey warming cabinet involves manually lifting about half a metric tonne. 

And that doesn’t include shaking off the few remaining bees which remain on individual frames. It’s not only my back that aches after this, but my fingers as well. Beekeeping, not such a gentle art as some might think.

I’ve previously noticed that more bees tend to remain in the supers if the colony is queenless.

This year the only queenless colony I found was also honeyless 🙁 

There was no need for the bees to remain in the supers … and no real evidence they’d been there in the first place.

This colony had a late queen mating fail (or perhaps lost on a mating flight) so I’ll unite it with a strong colony at the same time as I feed them and treat them for mites.

There’s obviously no point in feeding and treating before uniting or I’d jeopardise the reputation some beekeepers (including me 😉 ) have for being incredibly mean financially astute.

Lugless …

While shaking bees off one frame a lug broke. It’s a lovely frame of capped lime honey. Not close to show quality but pretty respectable all the same. I could scrape it back to the mid-rib and filter the honey or cobble together some sort of nail in place of the lug so I could spin it in the extractor. Instead I’m going to give it to friends who love honey direct from the comb … I’ll let them work out how to hang or stand it at the breakfast table.

The recovered supers were stacked on my honey warming cabinet set to 40°C. By the time heat losses are taken into account this maintains the supers at about 35°C, making the honey much easier to extract.

I usually rotate the stacks top to bottom and bottom to top a day before extracting. More lifting 🙁

Back in the apiary, the freed up clearers were placed under the supers on the remaining hives for collection the following day.

Storm Francis

Storm Francis only really arrived on the east coast of Scotland on Tuesday. It was windy and wet, but nothing like the pounding west Wales received. 

However, on early Tuesday morning when I arrived at the apiary it was wet.

Very wet.

There are few more demoralising sights than an apiary in really grey, wet and miserable conditions.

It was wetter and more miserable than this photo suggests …

There’s work to do and hives to open. Every single bee is ‘at home’. You know you’re going to get wet. It’s too blustery to use an umbrella and, anyhow, social distancing means there’s no-on there to hold one. 

Cold, clammy and heavy … a wet bee suit

The one saving grace is that the bees were incredibly calm.

I’d like to think they’ve been selectively bred over the years to be placid and well behaved, and that my skills as a beekeeper have been honed to the point where they barely know I’m there.

Hogwash.

It was so wet that they caused as little trouble as possible so that I got the roof back on the hive with the minimal delay 😉

Stings

Joking aside, these bees are calm and well behaved. Despite the flow being effectively over they haven’t become defensive. The majority of the colonies are very strong and they’re not being troubled by wasps, though these are searching out spilt honey and stores wherever possible. 

Our colonies in the bee shed are used for research and used to provide larvae and pupae for experiments. Members of my research team harvest brood when needed and, because they aren’t hugely experienced beekeepers, it’s important that the bees are not stroppy.

During the week I commented to a friend that I didn’t think I’ve been stung all season.

There may have been one of those glancing blows to a nitrile glove, but nothing that actually caused any pain or inconvenience.

Partly this is because I’ve done less beekeeping, but it also reflects repeated replacement of queens from stroppy colonies with selected calmer bees over past seasons. 

Aggressive bees do not collect more nectar. They are a menace to non-beekeepers and thoroughly unpleasant to work with. Fortunately, aggression is a relatively easy trait to select against and you can quickly see an improvement in colonies over just a couple of seasons.

Of course, I spoke too soon …

I lifted the lid on a stack of boxes containing old brood frames for melting down. To my complete surprise and considerable pain, I was greeted by a frenzied blitzkrieg of angry wasps.

Bang, bang, bang, bang, bang … BANG!

Five stings in less time than it takes to say it.

The final BANG was self inflicted as I hit the side of my head to try and squish a wasp before it burrowed into my ear and stung me.

Partial success … I crushed the wasp, but only after it had stung me on the cartilaginous pinna of my ear 🙁

I don’t know which hurt more … the sting or the blow to the side of my head.

These days I no longer bother setting wasp traps in my apiaries, instead relying on strong colonies (and reduced entrances or kewl floors) for defence. However, I’ve discovered that a strong washing up detergent spray is a good deterrent if wasps are getting into stacks of stored boxes. Spray the stripy blighters, stand back and let it do its work before blocking access with whatever you have to hand 4.

More bittersweet season endings

After about four days of intense beekeeping I’d removed all the supers, extracted the honey, collected the fondant, fed and treated all the colonies.

I’ll deal with feeding and treating next week (if I remember) but now need to rest my weary back and fingers … over the week I estimate I’ve lifted a cumulative total of 1200 kg of fondant and at least the same amount again of supers. 

The hives are now busy chucking out drones so they have fewer mouths to feed over the winter.

It’s a tough life being a drone in late August … but not for much longer

But to end on a more uplifting note, the honey crop was pretty good this summer 🙂