Category Archives: Problems

Early season inspections

Synopsis : The first inspection of the season needs to be late enough that the colony is expanding well, early enough that it isn’t making swarm preparations and timed to coincide with reasonable weather. Tricky. When you do open the hive you have to deal with whatever you find and leave the colony in a suitable state for the upcoming season.

Introduction

It is often tricky to decide when to do the first inspection of the season.

Too early and the bees will appear disappointingly understrength. If the weather is borderline you risk chilling the brood or the bees may get very defensive.

Or typically, both 🙁 .

Too late and the colonies may have backfilled the comb with early nectar and already started to make swarm preparations.

Early season – pollen pattie and brace comb

Twitter has been busy with beekeepers proudly announcing “8 frames of brood” or “Supers on this weekend”, without reference to local conditions or sometimes even their location.

Remember, some of these regular ‘tweeters’ are in France 😉 .

It must be particularly confusing for beekeepers starting their first spring with bees. They are desperate to start ‘real beekeeping’ again, which means opening colonies and looking for queens and brood, just like they were doing at the end of last season 1. However, they get dispirited if the colony is defensive or appears weak (less than 8 frames of brood!), and they kick themselves for not starting sooner if there are queen cells already present.

So what’s the best thing to do?

You have to use your experience and your judgement … or failing those, use some common sense.

I have reasonable amounts of experience and (sometimes) have good judgement, but I mainly rely upon a combination of common sense and local observation 2.

Together with a soupçon of opportunism.

Sometimes my timing is spot on, and sometimes I’m early or a bit late.

In these circumstances you have to deal with whatever you find in the colony and make the best of it.

A false start

Despite the incessant storms and getting trapped in a December blizzard (!) it has been a mild winter. We’ve had an unusually low number of frosts – none in January, one in February and two in March.

I was beginning to think that the season proper was going to start unusually early.

That was reinforced by the weather in the the last fortnight of March, which was fantastic.

Late afternoon sun on Beinn Resipol, Ardnamurchan, March 2022

Fantastic for March that is 3. Warm days, bees busy with the early season flowering gorse (it flowers all season), even a little nectar being collected.

About half my colonies had received an extra kilo or two of fondant in February or early March, and all received at least one pollen substitute pattie to help get them off to a good start. By late March the colonies were looking good 4.

I’m still a long distance beekeeper, with my colonies about equally split between the east and west coasts of Scotland. I therefore book hotels weeks or months in advance for some of my beekeeping. Predicting the weather that far ahead is impossible, so it involves some guesstimates and, inevitably, some beekeeping in unsuitable weather.

Early season is usually particularly difficult, but by late March this year I was feeling quietly confident 5.

And then April started with several hard frosts and the temperature dropped to single digits (°C) for days at a time.

Still, I was committed to make the trip to Fife … and I’m pleased I went.

And they’re off!

I have a couple of apiaries in Fife. I usually visit both on each of successive days on a trip. That allows me to store all the equipment in one apiary, without having to transport it back and forth across Scotland. This works well and means I can cope with most eventualities.

It was 9°C with a chilly easterly when I got to the first apiary. On removing the lid on the first hive it was very clear that I was (fashionably, of course 😉 ) late to the party … the bees were already building brace comb in the headspace between the top bars of the frame and the underside of the inverted crownboard.

That’s what you’ve been getting up to …

I had no spare equipment with me 6, but it was obvious that the colony needed a queen excluder and a super … as well as quite a bit of tidying up.

Which was going to be the story of the trip.

With infrequent apiary visits – either enforced by distance (in my case) or imposed by bad weather (not unusual in spring) – you have to deal with whatever situations you find when you have the opportunity to open hives.

It was clear from the state of this colony, which was on a single brood box, that the bees had expanded well during the warm weather and were going to rapidly run out of space.

Other colonies in the same apiary were on double brood boxes and were heavy with remaining winter stores – and, no doubt, some early season nectar – and reassuringly packed with bees.

It looked like a very promising start to the season.

More of the same

I travelled on to my main apiary to review the situation there. This is the apiary with my bee shed and all of my stored equipment. It is closer to the coast and the wind blows in directly from the North Sea.

It was colder and even less welcoming.

However, the bees were all in a very good state and clearly needed more space and a little post-winter TLC to get them ready for the season.

However, the temperature precluded any meaningful colony inspections. I could check for laying queens, get an approximation of colony strength (frames of brood) and give them space for further expansion. Anything more than this and there would be a risk of chilling the bees. Because of the low temperature I took relatively few photos.

Interestingly, colonies outside the bee shed were significantly better advanced than those inside. This is the first time I’ve seen this, and I’ve previously commented that the bees in the shed are often a week or two ahead of those outside.

However, in looking back through my notes I think it’s a reflection of the quality and early winter state of the colonies that currently reside in the shed. These are the ones mainly used for research and which regularly have brood ‘stolen’ for experiments (even late into the autumn). Consequently they were probably weaker going into the winter. At least one of the colonies had been united late in 2021 to ensure they would make it through the winter … and they had 🙂 .

What follows is a discussion of a few of the problems (and some potential solutions) that you can encounter at this time of the season.

‘Dead outs’ and ‘basket cases’

I’m not going to dwell on these as there’s not a lot to say and often little that can be salvaged.

Some colonies die overwinter.

I’ve discussed the numbers (and their questionable reliability) before. Most annual surveys show that about 10-35% of colonies die overwinter. The precise percentage depends upon the size and rigour of the survey 7, the severity of the winter 8 and the honesty of the beekeepers who respond 9.

Let’s just accept that quite a few colonies are lost overwinter.

I strongly suspect the majority of these losses are due to poor Varroa management. I’ve previously discussed the reasons uncontrolled mite levels are deleterious, and the – relatively straightforward – solutions that can be applied to prevent these losses 10.

It’s always worth conducting a post-mortem on ‘dead outs’ to try and work out what went amiss.

Queen failure

Some queens fail overwinter. This is probably unrelated to poor Varroa control and is ’just another thing that can go wrong’.

They either die, stop laying fertilised eggs or stop laying altogether.

They may or not be present when you check the colony in spring.

Whatever the failure, the overall result is much the same, although the appearance of the colony might differ (in terms of numbers of bees and the proportion of drones present). The colony will be significantly understrength, with little or no worker brood … and may have lots of drones.

I consider colonies with failed queens are a lost cause in March or (at least here in Scotland) much of April.

The bees that remain are likely very old. There’s no use providing them with a frame of eggs in the hope they’ll rear a new queen as it’s unlikely that there are sufficient drones about. If there aren’t flying drones I certainly wouldn’t bother.

You could provide them with a new queen if you can find one, but is it worth it?

The colony will be ‘well behind the curve’ in terms of strength for a month or two. You may have to boost them with additional brood. Unless you have ample spare brood in other colonies (as well as a spare queen and a willingness to commit these resources) I really wouldn’t bother.

Fortunately, at least so far (and I won’t be certain until later this month), all my colonies have survived and are flourishing … so let’s move on to a couple of solvable problems instead.

Brace yourself

When I add a fondant ‘top up’ to a colony I remove the crownboard and place the container of fondant directly over the cluster. This ensures that the bees can immediately access the fondant, rather than negotiating their way through a hole in the crownboard to the cold chilly space under the roof. To provide space for the fondant container I either use an eke or one of my deep-rimmed perspex crownboards.

A consequence of this is that, as the colony expands, they may build brace comb in the headspace over the top bars.

What a mess … some tidying required before the super can be added

Sometimes they fill the space entirely, though you might be lucky and find they’ve only built inside the fondant container.

Brace comb hidden inside the empty fondant container

Irrespective of the extent of comb building I usually take this to indicate that the colony needs additional space and that they should be supered.

Pronto.

Removing and reusing brace comb

I smoke the bees down – as gently as practical – and cut off the brace comb using a sharp hive tool. In the photos above the comb was filled with early season nectar.

When cutting off the comb I try and prevent too much of the nectar from oozing out and down between the frames. A sharp hive tool held almost parallel to the top bars is often the best solution. Working fast but carefully, I dumped the nectar-filled brace comb into the empty fondant container and then quickly checked the colony. The latter consisted of little more than gently splitting the brood nest and checking the approximate number of frames of brood in all stages.

I added a queen excluder, a super and a crownboard with a small hole in it, above which I placed the salvaged brace comb, surrounded by an empty super.

Crownboard and nectar-filled brace comb – stored overwinter and (hopefully) used in the spring

Finally, I added a second crownboard with some additional honey-filled brace comb they’d built last September. I wrote about this in Winding down last year. The intention is that the bees will take down the nectar/honey above the lower crownboard and either use it for brood rearing (if it’s too cold to forage) or store it properly.

If all this works as hoped the empty comb can be melted down and turned into beeswax wraps.

Waste not, want not 😉 .

The accidental ‘brood and a half’

My colony #7 has a stellar queen who produces prolific, gentle bees and who lays gorgeous slabs of brood with barely a cell missed. I used her as a source of larvae for queen rearing last season and will do so again this year.

“Gorgeous slabs of brood”

The colony entered the winter with a ‘nadired super’. I’ve discussed these somewhere before 11. Essentially this means a stores-filled super underneath the (single in this case) brood box.

Often the bees will empty the super before the winter and it can be safely removed.

Or, as in this instance, completely forgotten 🙁 .

When the bees had emptied it or not is a moot point … by last weekend they’d part filled it again.

With brood.

The queen had moved down into the super and laid up half the frames, at least two of which were drone comb 12.

I consider ‘brood and half’ an abomination. I prefer the flexibility offered by just one size of brood frame and also prefer using a single brood box if possible.

Despite perhaps swearing quietly when I realised the super was half-filled with brood (the drone brood was almost all capped) it’s only really a minor inconvenience.

Furthermore, this is a good queen and is likely to produce drones with good genes. How could I get rid of the ‘brood and a half’ setup as soon as possible and save all those lovely drones with the hope that they could spread their genes far and wide?

Upper entrances

The obvious answer was to add a queen excluder and a super, but to move the nadired super containing brood above the queen excluder.

If there had been no drone brood in this ‘super’ that would have been sufficient. However, drones cannot get through a queen excluder and distressingly 13 die trying.

Rearrangement to provide an upper entrance – before (left) and after (right)

I therefore added an upper entrance to the colony, immediately above the queen excluder. The easiest way to do this is to use a very shallow eke. I build them just 18 mm deep from softwood, with a suitably placed slot only half that depth.

The brood is directly above the brood box and so will be kept warm. The drones can emerge in due course, and fly from the upper entrance. Some will return there but – ‘boys will be boys’ – many will distribute themselves around the apiary waiting for better weather and potential queen mating.

Standard and upper entrance

If there is a strong nectar flow the bees can fill the new empty super and they will backfill the no-longer-nadired super once the brood emerges.

And finally … what did I fail to mention in this colony rearrangement ?

That’s right, the thing I failed to mention because I failed to check 🙁 ?

Where was the queen ?

It is important that the queen is in the brood box, rather than the no-longer-nadired super, when you reassemble the hive. If she isn’t, you’ll return to find two supers full of brood and an empty brood box.

A very quick check confirmed that the queen was in the brood box so I left them to get on with things.

Stores

I didn’t do a full inspection on any of the colonies I checked.

It was far too cold to spend much time rummaging around in the boxes. However, I did confirm that all were queenright and had brood in all stages.

I also ‘eyeballed’ the approximate strength of the colonies in terms of frames of brood. Typically this just involves separating the frames and looking down the seams of bees, perhaps partly removing the outer frames only to confirm things. Even just doing this I still saw a few queens which was doubly reassuring 🙂 .

The weakest colonies – those in the shed – had 3-4 frames of brood. The strongest were booming … perhaps even the 8 cadres de couvée 14 you read about on Twitter 😉 .

All of the colonies had ample stores, and several had too much.

The capped frames of stores were occupying valuable space in the brood box that the colony will need to expand into over the next 2-3 weeks. I therefore used my judgement to replace one or two frames 15 of capped stores with drawn comb or new frames. I save the frames of stores carefully and will use them to make up nucs next month.

Here are some I saved for later

I’ve heard mixed reports of winter survival and spring build up this year. I’m aware that some beekeepers in the south of England are reporting higher than usual colony losses. Others were reporting very strong expansion in the early spring and even a few early swarms.

It will be interesting to see how the season develops. As always it will be ’the same, but different’ which is one of the things that makes beekeeping so challenging and enjoyable.


 

It makes you go blind

Synopsis: There is a sexual arms race between the queen and the drones she mates with. The queen needs to mate with multiple drones to maximise colony fitness. Conversely, it’s in the interest of individual drones to reduce the number of additional partners who mate with the queen. Recent studies have demonstrated that drones reduce repeat mating flights by impairing the eyesight of the queen. Potential implications of this for practical beekeeping are discussed.

Introduction

Honey bee queens are described as polyandrous 1 because they copulate with multiple drones during one or more mating flights taken shortly after emergence.

These multiple matings are a risky business 2.

It takes longer to mate with multiple drones than it does to mate with one, but this time is minimised by reducing the number of mating flights. Rather than leaving the hive, mating once, returning and then repeating the process, the queen flies some distance to a drone congregation area and copulates with multiple drone before returning to the hive.

Shallow depth of field

One of many …

I’ve discussed the location and locating drone congregation areas previously and the distances the queens and drones respectively fly to reach these (which are different to avoid inbreeding).

Between the queen returning from the mating flight and the onset of egg laying there is a delay of a few days. During this period the queen is storing the sperm from the drones in her spermatheca. These are the sperm storage organs within which sperm stays active for years … a necessity as, after the onset of laying, the queen will not go on any more mating flights.

Perhaps surprisingly, only about 3-5% of the sperm transferred from each drone is stored by the queen.

I hope that makes you wonder why she bothers mating with so many drones … it should.

Polyandry and hyperpolyandry

Just before I explain why she only stores 3-5% of the sperm from each of several drones, rather than storing it all from one twentieth the number (and thereby reducing the risks of longer mating flights) of drones, I need to explain the poly bit of polyandry.

How many drones does the queen mate with?

The usual figures quoted are in the high teens, with a range extending from single digits into the low forties. These numbers are determined using a variety of different techniques, at least some of which are likely to underestimate the actual number of drones.

Marked queen surrounded by a retinue of workers.

Here’s one I made earlier …

Think of it like this, if you have a large population of something – like beekeepers – how many would you have to ‘sample’ to find one called ’David’.

Not many, it’s a common name.

But what about ’Atlas’ or ’Zebedee’?

You’d have to sample a lot more apiarists to find any with these rarer names, though I bet they’re out there somewhere. You might even have to use a different way to screen the population.

And it’s the same when determining the numbers of drones that the queen mates with.

Search and ye shall find – detecting rare patrilines

When you use a method that specifically looks for rare patrilines – essentially genetically distinct offspring fathered by different drones – you can find them. This suggests that the queen probably mates with more than the 15-19 drones usually quoted, and that hyperpolyandry is perhaps a better term to describe the mating behaviour of queen honey bees.

There’s evidence that these very rare patrilines (so-called ‘Royal patrilines’) are preferentially selected when rearing queens under the emergency response.

Colony fitness

So now we’ve defined what the poly in polyandry means … but we still don’t know why the queen risks all those aerial shenanigans to mate with so many different drones.

By mating with multiple drones she ensures that the workers in the colony are genetically diverse. This genetic diversity increases the rather-difficult-to-grasp concept of colony ‘fitness’. In this instance fitness is used to mean a combination of adaptability, resistance to stress or pathogens, increased foraging activity, better overwinter survival etc.

I’ve discussed this concept before and suggest you revisit that post for all the gory details.

The bottom line is that colonies that are headed by queens that are mated with very many drones (50+) produce more brood, have better disease resistance and have many other desirable traits (that benefit both the colony and the beekeeper).

The final piece of this introductory jigsaw I need to mention is that drone sperm is used randomly. It’s not a case of ‘first in, last out’. The 3-5% of sperm stored from each drone is mixed thoroughly in the spermatheca.

This makes sense in light of the comments above about colony fitness. If the sperm were used in batches from each drone you’d have cohorts of young bees being produced that had reduced genetic diversity, thereby potentially compromising colony fitness.

It takes two to tango

But let’s think about the poor drones for a moment.

Drones have two fates (excluding getting eaten by a bee eater); they either die while mating with a queen, or they get turfed out of the hive and starve to death towards the end of the season.

If the drone fails to mate with a queen he’s genetic dead end.

If he does mate with a queen there’s a good probability that the genes he carries will be passed on to the following generation.

There is therefore a lot of competition for the queen in the drone congregation areas (DCA).

The drones, once sexually mature, fly every (suitable) day to several DCAs, one after the other. In addition, they fly relatively short distances from the hive to maximise their time within the DCAs.

Heat map of the landscape used by drones – bright spots are DCA’s

This competition is intense, and it doesn’t stop once the drone has mated (and died).

If a queen mates with a relatively small number of drones – let’s say 10 for the sake of argument – the chance of the sperm from any one of those drones being used to fertilise an egg is much greater than if the queen had mated with 50 drones.

The fewer drones the queen mates with the better the chances that the genes from any one of her successful suitors will be passed on to the following generation.

Paradoxically, it therefore benefits the drone 3, if the queen mates with fewer other drones.

And, remarkably, drones have evolved a way to reduce the number of additional drones that a queen mates with.

A sexual arms race

Before I describe the mechanism, it’s worth emphasising here that best interests of the colony are served by the queen mating with many drones, but those of the drones are best achieved by limiting the polyandrous activity of the queen.

These two processes are therefore in direct competition.

There are some additional subtleties.

If the drone simply prevented the queen from mating again 4 it would be detrimental if that drone was the first with which the queen mated. The resulting colony would have little genetic resilience and would be unlikely to survive.

Any one drone must therefore allow the queen to mate with sufficient other drones to ensure colony fitness.

In addition, the more mating flights that a queen goes on, the greater the chances she will be predated by a passing bird, or get lost on the return flight.

From the drones point of view it would probably be beneficial for the queen to go on only one mating flight, but that she mates with sufficient (but no more than that) drones on that flight.

And finally, before I get to the mechanism by which all this is achieved – a compromise solution, like all the best solutions – I’ll remind you that studies have shown that queens go on about 5 mating flights spread over 3, usually successive, days.

Love is blind

At least, too much love is … 😉

Liberti and colleagues have recently published a snappily titled paper on how drones reduce the number of mating flights taken by a queen. The paper is Open Access so you can get all of the nitty-gritty details I don’t have time, energy or intelligence to include in the summary below.

The paper is:

Seminal fluid compromises visual perception in honeybee queens reducing their survival during additional mating flights by Joanito Liberti et al., (2019) eLife 2019;8:e45009

As with all science, the results published in this paper were a continuation of earlier studies of queen honey bees. In particular, these included studies by some of the same authors who had showed that seminal fluid contained proteins that had the ability to interact with neurons.

In addition, in Drosophila melanogaster (the fruit fly, and genetically best studied insect) there was evidence to suggest that seminal fluid promotes fast oviposition and reduces the willingness of females to seek additional copulations.

Drosophila mating in captivity

Now, Drosophila mating behaviour is very different to that of honey bees, but there was clearly a precedent here in which some of the components of seminal fluid – the ‘carrier’ that keeps sperm alive and motile and protects against pathogens – influenced subsequent mating in insects.

Or the lack of mating.

The study by Liberti et al., involves an elegant combination of hardcore molecular gene expression analysis coupled with electroretinography 5 and field work. I’ll skip briefly through the first two of these and provide a bit more detail on the last.

Analysis of gene expression

Virgin queen bees were instrumentally inseminated with seminal fluid (i.e. no sperm) or a control saline solution. Subsequent analysis of the brains of the bees – using a method called RNA-Seq which allows the qualitative and quantitative changes in gene expression to be accurately determined – demonstrated reproducible changes in the gene expression of dozens of genes.

Venn diagram of differential gene expression in instrumentally inseminated queen bees

Detailed analysis of which genes had changed in expression showed that several so-called signalling and metabolic cascades were modified in response to seminal fluid, and many of these mapped to the phototransduction pathways i.e. those involved in sight.

Several of the genes that were detected encoded proteins that were implicated in the conversion of light into the electrical signals in photosensitive electrical cells.

Inevitably, that one sentence has probably confused half the readers that have persevered to this point in the post …

Essentially what this means is that there are components within drone seminal fluid that change the ability of the queen to perceive light, or to see.

So, do they?

Visual perception of queens

The gene expression studies in this paper are complicated (for a molecular biologist). The electroretinography is an order of magnitude more complicated for this molecular biologist to understand … but here goes.

Electroretinography involves measuring the electrical signals generated by particular neurones that are connected to the compound eyes and ocelli 6. This allows the consequences of the changes in gene expression to be determined in terms of the vision of the queen bee.

These studies showed that queens instrumentally inseminated with seminal fluid had lower responses to low frequency flickering light, and that that this response (or lack of response) increased on the second day after insemination.

There were additional changes in the response of the ocelli in queens inseminated with seminal fluid.

Taken together, these results show that queens exposed to seminal fluid experience reduced visual performance.

They are not blinded, but their vision is impaired.

Does this visual impairment have any influence on their mating behaviour?

Mating flight behaviour

Finally, we come to something that’s a bit easier to comprehend, not least because I’ve previously discussed the technology used – the RFID tagging of individual bees to monitor their flight frequency and duration.

RFID-tagged queens (34 in total) were instrumentally inseminated (either mock, or seminal fluid or semen) and subsequently monitored when going on mating flights. Those receiving either seminal fluid or semen were more likely to get lost on these flights, and repeatedly triggered the hive entrance sensors, suggesting they were disorientated by sunlight after leaving the hive.

Of the 21 queens that returned, 81% went on mating flights of more than 7 minutes which was considered a conservative threshold for a completed mating flight i.e. flight to a DCA, mating(s) and return to the hive, and about 50% laid worker brood.

Notably, of the 17 queens that went on ‘successful’ (by duration, not necessarily by outcome) mating flights, those receiving the control saline solution left 1-2 days later than those that had received seminal fluid or semen.

Seminal fluid and semen induce alterations of mating flight behaviour in honeybee queens

These results show that exposure to seminal fluid induces significant changes in queen mating flight behaviour, presumably as a consequence of the alteration to the vision of the queen.

Therefore, the implication from these results is that proteins in the seminal fluid of drones impairs the visual perception of queens, thereby reducing the likelihood that the queen will embark on additional mating flights.

Queens that had already mated (or been instrumentally inseminated in this study) were more likely to get lost on subsequent mating flights, and embarked on these flights earlier.

But what about swarming?

The hive – or a natural nest site – is a low-luminance environment. Queens do not need fully functional eyesight once they have returned from their mating flights. In the hive communication is non-visual, mediated by pheromones, contact, vibrations and sound.

However, although a queen only goes on a few mating flights, she will also leave the colony if it swarms.

Swarm of bees

Swarm of bees

What are the implications for the this study on the eyesight of queens during swarming?

This isn’t really discussed in the paper, but I think there are two likely scenarios:

  • the changes in visual perception by the queen are transient and return to ‘normal’ after a few days, weeks or months
  • swarming is a fundamentally different activity in which thousand of bees leave the hive and for which accurate vision is not needed by the queen.

There’s a world of difference between embarking alone on a mating flight of several kilometres and having to return to the exactly the same location, and leaving on a one-way trip with a swirling mass of attendees with dozens of scout bees leading the way.

Further studies will be needed to determine whether the changes in vision are transient or permanent, as well as to identify the ‘active ingredient’ in seminal fluid that is responsible for the degradation of the mated queen’s vision.

I also think further studies will be required to determine the relationship between dose and timing of the response.

How long does it take for the reduction in visual perception? If the first and second mating flight are taken on successive days is the “return rate” greater than if they are taken a few days apart?

How many drone matings are needed to reduce the visual acuity of the queen? I would predict that this would be a number consistent with the lower estimates of polyandrous matings needed to generate fitness in the resulting colony.

And implications for practical beekeeping?

Perhaps none directly, though I’m interested in the answers to the questions I posed in the paragraphs above.

In an area with low drone densities and those with shall we say ‘variable’ weather – such as my apiaries on the west coast of Scotland (or for that matter, any beekeepers living in remote northerly areas with just a few hives) – is colony fitness compromised by reduced matings?

An isolated apiary

Conversely, is mating success lower because more queens fail to return from subsequent mating flights that they have to take to try and mate with enough drones?

Can mating success and colony fitness be increased by boosting drone numbers?
And is this achievable at a scale meaningful to a small-scale beekeeper?

If a measurable increase in mating success took a 1000-fold increase in drone numbers it’s probably not achievable.

However, if all it took was an extra frame of drone comb in every hive in the apiary, then that’s quick win.


 

Tragedies and triumphs

Synopsis: Beekeeping shouldn’t be “a series of calamities then winter”, though it sometimes feels like that. In the first of a two-part post I look at the real and imagined disasters that can befall you during the season. The reality is that the observant and well-prepared beekeeper can avoid most of the ‘tragedies’, and recover from almost all of them.

Introduction

A few weeks ago I did a live-streamed Q&A with Laurence Edwards from Black Mountain Honey. Some of the questions were both good and interesting, some of the answers were perhaps less so. Before any readers think I’m being rude here I should point out that Laurence was asking the questions – often on behalf of others – and I was answering them.

There were quite a few questions on non-chemical treatment which I was singularly ill-equipped to deal with. Not because I don’t know anything about it, but because I don’t practice it 1 and because I suspect I’m not a good enough beekeeper to be successful if I did try it. There’s clearly a lot of interest in the topic, though I fear much of this is also from beekeepers who are not sufficiently experienced to succeed with it either.

However, there were two questions – or perhaps it was one merged question – that went something like this:

What is your greatest beekeeping success and your biggest beekeeping disaster?

I’m paraphrasing here. I can’t remember the precise wording and daren’t review it on YouTube as I’d then have to listen to my erudite insights inchoate waffle … which would be excruciating.

My answer probably involved asking whether I was restricted to just one disaster … 😉

Let’s get some perspective first

New beekeepers in particular are likely to worry about the “disasters” and overlook some of the “successes” in their first season or two. I therefore thought I’d discuss what I consider are the highs and lows – abbreviated to tragedies and triumphs’ to give the post a snappy title – of the first few years of beekeeping.

Obviously this is biased and based upon my own experience, and from mentoring others. Your experience may be very different … or you may have yet to experience the highs and lows of a beekeeping season.

But before I start using superlatives to describe the chaos of my early efforts at swarm control it’s worth remembering – particularly as the war in Ukraine enters its third week – that I’m only talking about beekeeping here.

In the overall scheme of things it’s simply not very important.

What might feel like a disaster of biblical proportions in the apiary … isn’t.

Yes, it might threaten the productivity, or even the survival, of the colony, but it is only beekeeping 2.

So, having got that out of the way, which do you want first?

The good news or the bad news?

The bad news … how mature 😉

The loss of a hive tool

Clearly I’m being flippant here.

The loss of a hive tool is a minor inconvenience rather than a tragedy.

There you are!

Unless you don’t have a spare and/or you’re about to inspect a dozen heavily-supered hives in the apiary … in which case it’s a major inconvenience.

It’s remarkably easy for a hive tool to fall out of those tall, thin pockets in the sleeve or thigh of your beesuit. Inevitably it falls, not onto closely cropped sward, but into tangled tussocks of rarely-mown grass.

You will probably find it again.

You could spend 15 minutes on your hands and knees retracing your steps since you left the car or you could become a detectorist and conduct a grid-based search, sweeping the area for metal objects.

Neither method is guaranteed to work.

To be certain, you must cut the grass.

But be careful. A glancing contact with the lawnmower or brush cutter and a half-buried hive tool will be damaging at best, and potentially a lot worse 🙁

Hive tools soaking

Hive tools soaking in a solution of soda crystal

Or you can avoid all this grief by keeping a covered bucket in the apiary – a honey bucket is ideal – containing a strong solution of soda crystals. You know exactly where the hive tools are and you soon get into the habit of dropping it back in after an inspection.

Better still, keep two hive tools in the bucket and alternate them as you look at your colonies. The soaking in soda will clean the hive tool, reduce any potential cross-contamination and improve your apiary hygiene.

The loss of a queen

This can be anything from a minor inconvenience to a bit of a calamity.

It very much depends upon the:

  • time of the season
  • whether you notice she’s missing
  • availability of a spare colony

How do you lose a queen? Other than by losing a swarm (see below) the two most likely reasons are cackhanded beekeeping or a queen that fails due to being poorly mated.

Returning a marked and clipped queen to a nuc

Losing a queen mid-season, for whatever reason, should be little more than a minor inconvenience. Assuming you notice she’s missing in action you can remove unwanted queen cells, leaving a single charged (i.e. known to contain a fat larva lounging around on a comfortable bed of Royal Jelly) cell, and wait while she pupates, emerges, mates and starts laying.

Nerve racking? Perhaps slightly, but it’s usually a pretty safe bet that things will work out OK.

If, through clumsiness or stupidity 3, you kill the queen during an inspection there should be ample eggs and young larvae for the colony to use when rearing one or more replacements.

Keep your eyes peeled …

But what if you don’t notice she’s missing? You assume she’s there and blithely knock back all the queen cells you can find 4.

Sealed queen cells

You return the next week … all looks good, no more queen cells.

But wait a minute … there are no eggs either 🙁

Under these circumstances you realise the importance of having at least two colonies. You can rescue the queenless colony by donating a frame of eggs from a queenright colony.

With two hives a crisis is rarely a disaster

Queens also fail because they are poorly mated. They either stop laying, or they stop laying fertilised eggs (i.e.they continue to lay unfertilised ones, leaving you with ever-increasing numbers of drones in the colony). The colony might realise and supersede her, or you might be able to rescue the situation with a donated frame of eggs.

I’ll deal with the consequences of a failed or slaughtered queen at the extremities of the season – early or late – below.

The loss of a swarm

It happens to the best of us, and it sometimes seems to happen even if you do your swarm prevention and control by the book 5.

I’ve turned up in the apiary on a warm May afternoon to discover a whirling mass of bees swarming from one of my hives 6.

It’s not a disaster … in fact it’s one of the greatest sights in beekeeping.

With luck the swarm will bivouac nearby and you’ll be able to collect them in a skep and re-hive them late in the afternoon.

A small swarm

A small swarm …

At least it shouldn’t be a disaster, but Sod’s Law usually dictates that …

  1. if you’re there when the swarm emerges, and
  2. you have a skep and sheet with you

… the swarm will alight 45 feet up a Leylandii 🙁

Even then it might end well if you’ve got a suitable bait hive set out nearby.

The time when losing a swarm is a disaster 7 is when you don’t realise you’ve lost a swarm. You find some queen cells, hurriedly knock them all back 8 and then wonder why there are no eggs the following week.

Déjà vu

At which point you’re in a similar situation to the ‘loss of the queen’ I described above … except you’ve also lost up to 75% of the workers from the colony. The situation is still rescuable with a frame of eggs from your other hive 9 but you’re likely to miss out on the major nectar flow.

Could the situation be any worse?

Oh no it can’t … Oh yes it can!

You miss the lost the swarm, you knock back all those queen cells and you then fail to realise there are no eggs or young larvae in the colony until only sealed brood remains (i.e at least 9 days).

Or worse still, until no brood remains (i.e at most 21 days).

With no brood pheromone being produced there’s now a real danger that the colony will develop laying workers. Things now get an order of magnitude more difficult as a colony with laying workers is very difficult to requeen (and generally will not even attempt to rear their own if presented with a frame of eggs).

Drone laying workers ...

Multiple eggs per cell = laying workers (usually)

You’re fast approaching the next of the beekeeping ‘disasters’ …

The loss of a colony

How do you lose a colony?

What was it Elizabeth Barrett Browning said? ’Let me count the ways’ 10.

Natural disasters such as falling trees, winter gales, raging floods, woodpeckers, honey badgers and stampeding elephants 11 can destroy a colony.

Hive toppled by a summer storm

However much care you take – avoiding floodplains, strapping the hives down, seeking shelter (but not near shallow-rooted trees) – sometimes sh1t just happens 12.

You did your best and nature did her worst.

See what you can rescue and try again next year.

Queen loss at the start or end of the season

Losing a queen very early or very late in the season – for whatever reason – is a problem. There’s no chance of the colony rearing another – it’s too cold and/or there are no drones available. I suppose there’s an outside chance you could requeen the colony – if you had a queen available 13 – but doing so involves quite a bit of risk.

If the queen fails overwinter, all the bees in the box will be very old by the time your colony inspection confirms she’s firing blanks, or not firing at all. The chances of successfully requeening the hive are slim at best.

Although that colony is effectively lost – at least if it happens late in the season – it’s not an unmitigated disaster if you have another hive 14. You can unite the queenless colony over a queenright colony very late into the autumn, strengthening the latter and (at least) using the bees from the former, rather than condemning them to a lingering death.

An Abelo/Swienty hybrid hive ...

An Abelo/Swienty hybrid hive … uniting colonies in midsummer

I wouldn’t bother trying to unite a queenless colony (or one with a failed queen) at the very beginning of the season. The remaining bees will be pretty decrepit and there won’t be many of them. It’s unlikely they would contribute in a meaningful way to the successful build-up of another colony.

Winter losses through starvation

These are unfortunately common and often entirely avoidable.

Small-scale surveys from the BBKA and SBA often report winter colony losses of 20-30%, and up to 50% in some years. Large scale surveys, like the Bee Informed Partnership (BIP) one in the USA, have reported annual colony losses – the majority of which occur in the winter – exceeding 40% in all but two years since 2013.

Bee Informed Partnership loss and management survey

I’ve lost colonies through both starvation and disease.

In both cases it was entirely my fault 🙁

It was a disaster for the bees and it was a sobering and educational experience for me.

I discussed starvation, and how to avoid it, in winter weight a couple of weeks ago. I won’t rehash it here, but I will repeat again that the bees are still in the ‘danger zone’.

Time for another?

Time for another? Definitely.

There’s little nectar available and they are busy rearing brood. Their need for stores is probably higher now than at any time over the last 4-5 months.

At best, a shortage will hold the colony back. At worst they’ll die of starvation.

All of which is completely avoidable by ensuring they have ample stores at the beginning of the winter, and then by keeping an eye on the weight of the colony as they enter the spring. If you’re adding fondant in late December it’s likely the colony had insufficient stores to start with … but at least you’re keeping a check on the weight of the colony.

Winter losses due to disease

I suspect that the majority of winter losses are not due to starvation but are instead due to inadequate or incorrect Varroa management.

This is a topic that has been covered numerous times in posts here. The most recent overarching review of the topic is probably Rational Varroa Control. Versions of this appeared in the August 2020 BBKA Newsletter and in The Scottish Beekeeper in the same month.

Successful Varroa control requires an understanding of the treatments available and the pros and cons of using them on your bees and in your location/climate. Too many beekeepers simply want to know whether they should add Apiguard in the third week of August or middle of September.

Apivar strip on wire hangar

Unfortunately, it’s not quite that simple.

But that doesn’t mean it’s particularly difficult either.

Unlike many of the other diseases of honey bees – e.g. chronic bee paralysis virus (CBPV), Nosema and the foulbroods – there are effective treatments to control Varroa and the damaging viruses that it transmits.

Losing a colony in June to CBPV is possibly unavoidable (it’s just bad luck) but losing one to Varroa/DWV in January – which is largely avoidable – might well be bad beekeeping.

In both cases of course it’s a disaster for the colony 🙁

Disaster

The meaning of disaster is ‘An event or occurrence of a ruinous or very distressing nature; a calamity; esp. a sudden accident or natural catastrophe that causes great damage or loss of life’. Its origins date back to the mid-16th Century.

Some of the ‘disasters’ I’ve described above involve the loss of just one life – that of the queen. For the reasons I describe, they’re not really disasters at all, or shouldn’t be for the observant and well prepared beekeeper.

Locally bred queen ...

Locally bred queen …

They become disasters i.e. causing great damage or loss of life, if you miss the tell-tale signs and so contribute to the eventual demise of the colony.

The avoidable loss of a queen or a colony is a distressing experience, or at least it should be 15.

If it is distressing then it will probably also be a learning experience.

Analyse what went wrong and work out how you might prevent it happening again in the future.

We have a duty of care for the bees we manage. I don’t like losing colonies, but it still happens infrequently. When it does I try and determine whether it was just fate … or my incompetence (or – let’s be generous – my actions or inactions) that caused the loss.

And the times you manage to work out where you went wrong are the foundations for your beekeeping triumphs in the future … which is what we’ll return to next week.


 

Queen mating flights

Synopsis: How far does a queen fly to mate? Studies using RFID-tagged queens are providing insights into the frequency, duration and temperature dependence of queen mating flights … all of which have practical implications for beekeeping.

Introduction

Although it tends to be a rather poor topic of conversation at dinner parties 1, I’m getting increasingly interested in the mating biology of honey bees. This is an essential part of the life cycle of our bees, and one that has been – and continues to be – well studied.

Marked queen surrounded by a retinue of workers.

Here’s one I made earlier …

When I lived in the Midlands there were a seemingly endless supply of bees in the area. Beebase reported that there were about 200 other apiaries within 10 km of my main apiary. Assuming an average of 5 hives per apiary 2, and ignoring any wild or feral colonies, that’s 1000 hives producing drones with which the queen could mate 3.

Of course, it’s not quite that simple, but bear with me.

In Fife, on the east coast of Scotland, my apiaries are in areas with about 35-40 other apiaries within 10 km, so – using similarly dodgy maths – perhaps 200 hives.

Nevertheless, bees are in apparently plentiful supply.

What do I mean by ‘plentiful’?

As a beekeeper, the two main ways – other than Beebase or by physically searching for them – I can judge the numbers of bees in the environment are, the:

  • success of my bait hives in attracting swarms 4, and
  • the ease with which my queens get mated

If I catch lots of swarms and a high percentage of my queens mate successfully then there must be a lot of bees about.

Apiary density

I was intending to start this post with a discussion of the evenness or otherwise of the distribution of apiaries within the Beebase-defined 10 km radius.

However, it turns out 5 that my maths are not good enough to plot a truly even distribution of hives/apiaries 6. Anyway, common sense dictates that apiaries are not evenly distributed … so let’s instead just consider the number of hives per square kilometre within that Beebase 10 km boundary.

Neighbouring apiaries, hive density and queen mating distances (see text for details)

In the diagram above the enclosing black circle indicates the area within which Beebase reports ‘neighbouring’ (i.e. within 10 km) apiaries. Inside that I’ve shown just four of the 314 one km2 blocks (in blue). On average, in the Midlands each of these would contain ~3.2 managed hives 7. In Fife, there would be – on average again – about 5 times fewer hives per blue square.

Several studies suggest that drones fly relatively short distances from the hive to the drone congregation areas (DCA) where they loiter with intent’ (of finding a virgin queen to mate with). I’ve discussed the use of harmonic radar tracking studies to identify these locations.

So, how many of these hives are actually within the range of a queen on a mating flight?

Where do you go to my lovely?

I posed the question How many of these hives … ? as we don’t know where the actual DCAs are.

The radar mapping study identified several within a few hundred metres of three drone producing colonies, so it seems reasonable to simply assume the DCAs are near the hives, and we know the average density of these.

Harmonic radar tracking of tagged queens visiting DCAs was not successful. It’s a short range technique, and the queen is known to sometimes fly long distances to visit DCAs.

I’ve discussed some of the studies used to determine these long-distance virgin queen flights, but summarise them again here:

  • In studies almost 90 years ago, Klatt observed successful mating on an isolated peninsula when the queen and drones were 6.3 miles (10.1 km) apart
  • In the mid-50’s Peer 8 demonstrated matings could occur when the queen and drones were 10.1 miles (>16 km) apart
  • Jensen 9 demonstrated mating when the queen and drones were 9.3 miles (15 km) apart

Of course, in all these studies it was not determined whether the queen and drones flew similar distances to the DCA. Since we know that drones probably fly relatively short distances it’s likely that the queen does the majority of the leg wing-work.

Ignore the outliers

The Peer studies showed that, although mating could occur when drones and queens were very widely separated, there was an inverse relationship between mating success and distance.

Just because 5% 10 of queens can mate following combined flight distances of 15 km does not mean that’s the distance they usually travel.

Actually, if only 5% of queens get mated at that distance then we can be pretty sure they usually fly much shorter distances.

Fortunately, Jensen did a more thorough analysis of this and showed that 90% of all matings occurred within 4.6 miles (7.4 km) and 50% within 1.5 miles (2.4 km).

And those are the 50% and 90% circles plotted on the diagram above, encompassing an area of 18 km2 and 174 km2 respectively.

Or, to express that area in potential drone donor colonies, 58 or 548 respectively in the Midlands, with a hive density of 3.2/km2 11.

So, in areas with reasonable densities of bees, knowing the majority of queens fly no more than 7.4 km, there are potentially hundreds of colonies producing drones that the queen could mate with.

All of which is a rambling introduction to looking at queen mating distances using a different approach.

Rather than work out how far she flies, what happens if we measure how long she takes?

If we know how fast the queen can fly we can again calculate distances and the number of potential drone producing colonies within range.

Time and weather dependence

But there are additional advantages of looking at queen mating flight duration.

If we can do it accurately we can also determine the:

  1. time of day when most mating flights take place,
  2. influence of the weather on the duration and frequency of queen mating flights,
  3. number of orientation and mating flights the queen takes.

And frankly, as a practical beekeeper, I’m much more interested in the first two of these than I am in the absolute distance she flies for her dalliances.

In an area well-populated with hives, understanding when the queen is likely to be away on a mating flight will help me avoid interrupting her return, and determining when she is likely to start laying.

But, as a scientist, I’m also really interested in the third point as there is some interesting recent work to suggest that drones try and restrict queens taking multiple mating flights 12.

Heidinger et al., studied the mating behaviour of queens using radio frequency identification (RFID) tags 13. Although the study produced no dramatically new results, it was a neat application of technology and allows me to discuss when mating flights occur and the influence of the weather in a little more detail.

The paper is Open Access if you’d like to read it. I’m not going to go through every subtle wrinkle and nuanced argument in the study, but will instead just focus on the important ’take home message(s)’.

RFID tagged queens

This is something I don’t need to discuss in anything other than cursory detail as I wrote about it three weeks ago in ’Chips with everything’.

Or perhaps I do? The post was only read by about 25% of the visitors who read the following week’s ’What they don’t tell you’ … it’s almost as though the hardcore science is less interesting than anecdotes about starting beekeeping. Surely not?

Essentially you stick a unique tag onto a bee and record when it enters or exits a hive using a sensitive reader at the hive entrance.

RFID tagged bees and RFID readers on a feeder

You don’t need to stand by the hive and watch anything.

All the ‘observations’ are made automagically and recorded digitally for subsequent analysis. You can therefore monitor hundreds of workers or dozens of queens simultaneously, thereby increasing the statistical robustness of the results obtained.

The Heidinger et al., study monitored the mating flights of 64 queens.

Of these, 11 were ‘missing in action’ 14 and never returned to the mating nuc.

Fifty three (83% … a figure very close to that quoted above from completely different studies) mated successfully and started laying eggs. However, two of these managed to get out and mate successfully without ever being detected by the RFID reader, meaning that flight times, frequencies and durations are from 51 queens 15.

The study was conducted in two apiaries about 4 km apart in Middle-Thuringia, Germany, in June/July.

Logistics and data wrangling

Conducting these types of field studies is not straightforward. Queens have to be produced in batches and then introduced to mating nucs.

A week of bad weather means the queens will have aged before they have a chance to fly.

What do you do about queens that return from a mating flight but that cluster underneath the mating nuc, only entering (and triggering the reader) after an hour or two?

To accommodate these vagaries the authors:

  • grouped queens according to age,
  • considered flights less than 3 minutes long as orientation flights
  • ignored mating flights of longer than one hour

And whatever filtered through from that pre-screening was then subjected to rigorous statistical analysis.

Time and duration of mating flights

Queens went on mating flights for 1 to 5 days, with an average of 2.2 +/- 0.98 day 16. In easier-to-comprehend terms this means that about 70% of all the queens went on mating flights on 1 to 3 days.

Since it’s often quoted that queens leave the hive ‘once to mate’ this might be a surprise to some.

Perhaps even more surprising is that queens went on a total of 1 to 16 mating flights, with an average of 5.04 +/- 3.11.

One particularly enthusiastic queen went on 7 mating flights in one day. The very definition of ’hot to trot’.

The timing of queen mating flights

Over 80% of these mating flights took place between 1pm and 4pm. From a practical beekeeping standpoint, by avoiding this period for hive inspections you will significantly reduce the chances of being in the way when a queen returns to a mating nuc.

The duration of mating flights

The average length of a mating flight was a bit less than 18 (17.69 +/- 13.19) minutes. Of approximately 255 mating flights (i.e. flights of 3-60 minutes duration) monitored, about 180 (70%) were of 20 minutes or less.

All of these results are in pretty good agreement with a wealth of literature collected using different methods over the last few decades.

Can we use some of these figures to calculate queen mating flight distance?

Duration x speed = distance

I can find nothing in the literature on the speed at which a queen flies. However, I do know that the escapee virgin queens I try and catch usually fly just too fast 🙁

Let’s assume for the sake of argument that the queen flies at about the same speed as a worker bee. This is usually reported as 25 km/hr unladen and about 17 km/hr when laden with pollen or nectar.

Therefore, a queen mating flight of 20 minutes at 25 km/hr involves flying a total distance of no more than 8.3 km. A 10 minute mating flight at 17 km/hr equates to 2.8 km.

These distances include three components, an inward and outward leg separated by the flight time within the DCA. Your guess is as good as mine as to how long the latter takes 17.

However, not knowing something is the perfect opportunity for some informed speculation (or, as here 18, wild guesswork).

Wildly uninformed guesswork

The queen mates with several drones while in the DCA. Although each mating takes a very short time (seconds) there is competition between the drones while they chase the queen, so she must stay within the DCA for a reasonable period.

Time for another assumption … this time let’s assume that the queen spends one third of the duration of her mating flight within the DCA or 4 minutes, whichever is the shorter 19.

If that were the case, a 10 minute mating flight at 17 km/hr, with a third of the flight time being spent in the DCA, would mean the mating site was just 940 metres from the hive. Conversely, if the queen spent no more than 4 minutes in the DCA during a 20 minute mating flight at 25 km/hr, then the mating site must be 3.33 km from the hive.

Either my guessestimate for the time spent in the DCA is too high (quite possible), or the predicted flight speed of the queen is too low (unlikely to be wildly wrong, she’s not going to rush there at 75 km/hr) … or the typical distances queens travel to a DCA are significantly less than those measured using isolated queen and drone-producing colonies in the studies cited earlier by Jensen, Peer or Klatt (see above).

Relationship of time spent in DCA and potential maximum mating flight distance

The table above shows why I think queens likely spend less than 4 minutes in the DCA. Distances in red are within 2.4 km that Jensen showed 50% of matings occur in, those in yellow are within the 7.4 km that 90% of matings occured in 20.

The influence of the apiary

Let’s stop all this wild guesswork and return to the calming certainties of statistically compelling data 😉

The Heidinger study involved two apiaries separated by a few kilometres. All the data discussed above uses recordings pooled from both apiaries. However, queens in one apiary went on more mating flights than in the other. The difference isn’t huge (5 vs. 4 flights in the first three flight days), but is statistically significant.

Mating flight number (a) in different apiaries, and (b) at different temperatures

The queens are described as ‘sister queens’ and I assume this means they are all reared from larvae from the same mother queen, though this isn’t made explicit. If that is the case, it suggests the geography of the area influences queen mating flight frequency.

I say geography, rather than drone availability, as they also added an additional 47 (!) drone producing colonies near one apiary and observed no influence on queen mating flight characteristics.

Although the number of mating flights the queens went on differed, the duration of the flights did not.

The data start to get a bit more complicated when they considered the age of the queens and the duration of the first, second, third etc. flight … so I’ll skip all that and finally just consider the influence of temperature on mating flights.

Some like it hot

It is regularly stated that virgin queens need calm, sunny afternoons with a temperature exceeding 20°C before embarking on mating flights.

This is somewhat disconcerting for a beekeeper living on the cool/wet/windy – but exceeding beautiful – extremities of the UK.

July rain squalls across Mull, Skye and the Sound of Sleat

In fact, mating flights – by which I mean flights of 3-60 minutes (as no record of successful mating on individual flights was made) – occurred in the Heidinger study between a range of 14°C and 25°C.

In cooler weather, queens tended to take more mating flights (shown in the right hand panel on the graph above). The line is a ‘best fit’ and it’s clear there is quite a bit of variation. However, at 15°C the queens would take about 7 flights, compared to only about 4 flights at 24°C 21.

Unsurprisingly therefore, individual mating flights were of greater duration during warmer weather. Again the ‘best fit’ line is shown together with the variation in the primary data.

Relationship between temperature and individual mating flight duration

I found these last two graphs quite reassuring … there were lots of flights below 20°C.

Geek alert

I’m starting to get a bit obsessed with the weather here on the west coast and installed a weather station last summer. I only have complete records from July, but know we had a total of only 27 days on which the temperature exceeded 20°C from July and September.

August 2021 temperatures in Ardnamurchan

2021 was an outstanding summer here on the west coast.

Next year I’ll have data for the full queen rearing season so hope to understand this aspect of the mating biology of my queens a little better.

Conclusions

I’ve covered a lot of ground in this post … from the how far can she fly to mate? studies of the 1930’s to what appear to be short duration, and therefore relatively local, mating flights of RFID-tagged bees.

Understanding when a queen is likely to go on a mating flight should help you with timing your colony inspections. It should certainly help curb your impatience as you wait for your queens to get mated.

Finally, knowing that she can fly on much cooler days than the widely-cited 20°C gives those of us living in more northerly latitudes some reassurance that our queen rearing efforts are not entirely futile.


Notes

Some figures I meant to quote earlier; if the queen only flies between 940 m and 3.33 km to the DCA (see Duration x speed= distance above), and assuming colony densities of either 0.6/km2 or 3.2/km2 (see Apiary density about 3000 words ago 🙁 ) the number of hives ‘within mating flight range’ are between 1.7 and 111.

Quite a range, so ample opportunity for good numbers of genetically diverse drones, though remember that apiaries are not evenly distributed and DCA’s are variable distances from drone producing colonies.

Treat all of my numbers (and particularly my calculations) with considerable caution.

Chips with everything

Synopsis: How do you accurately measure flight times and durations of hundreds of bees? And why would you want to do this anyway? Using the same technology as Marks and Spencers label stock items, albeit on a smaller scale, it is now possible to monitor thousands of honey bee flights very accurately.

Introduction

As a beekeeper, you’re well aware of the size and appearance of a honey bee. Considering the workers only, they are all pretty much the same size and they all look rather similar.

Yikes … I’m only two sentences into the post and I feel the need to add a couple of interesting caveats:

  • honey bees are unusual (amongst bees) in that there is much less variation in the size of individual workers within the population 1. This might aid the accuracy of the waggle dance … 2
  • however, that size is not constant. For reasons that are not really understood, the size of honey bee workers increases during the season, by a small but significant amount 3

OK, let’s get back on track …

Considering this similarity, how can you tell if and when a particular bee returns to the hive?

For example, if you’re interested in the distance from which a bee can successfully return to the hive.

The obvious thing to do is to mark the bee, in the same way you would mark a queen, with a small coloured spot of paint on the thorax.

Small bees, big numbers, Posca pens

But, returning briefly to that very slight increase in size of honey bees during the season, scientists often need to make multiple repeat observations to get statistically significant results 4. This becomes a problem as Posca only do a limited range of colours … you might be able to label bees with only eight different colours.

Mr Blobby goes beekeeping

Or 64 combinations if you use two colours per bee … or 512 if you use three colours together.

There are problems with this. Firstly, it takes a lot of time to put two or three separate dabs of paint onto the thorax of a worker bee. Secondly, the thorax is a rather small target for a rather fat pen (do you remember your first attempt at queen marking? 😉 ).

One way round this is to add dabs of paint to the abdomen as well, or instead, of the thorax. A bigger target certainly, but there are then issues with ensuring flexibility and not blocking the spiracles and a host of other things, so not ideal.

But, even if you could label a few hundred bees with unique colours, you’d then have to sit next to the hive entrance for hours at a time recording the arrival of blue-green-red (or was that green-red-blue? 5 ).

Not ideal … particularly if you are colourblind.

Actually, almost impossible.

But, thanks to Leon Theremin, the Russian inventor of the eponymous musical instrument and developer of the spookily named listening device “The Thing”, the RFID tag was created.

“The Thing”

The Thing” was a covert listening device hidden in a plaque proudly displayed inside the American ambassador’s Moscow residence for seven years 6. It was a so-called ‘passive cavity resonator’. When energised by a radio signal of the correct frequency (which – surprise, surprise – was transmitted by the Russians) it would pick up sound waves from the room, causing a membrane to vibrate. This vibration could be detected by a receiver (which – you guessed it – the Russians also had) and a decoder, thereby allowing conversations to be heard.

искусный as they say in Russian 7.

RFID tags and honey bees

And, on a somewhat smaller scale, that’s pretty much how radio frequency identification (RFID) works.

There are two components:

  • an RFID tag or chip which is attached to whatever you want to uniquely identify. You’ll be entirely familiar with these are they are often attached to price tags of items in shops (where they are used for stock control). They essentially consist of a microchip and an antenna.
  • an RFID reader which emits the radio signal to activate the tag and then ‘reads’ the information sent back. Typically this information includes a unique serial number 8.

RFID tags can be tiny. Hitachi make one that is 0.0025 mm2 which can store a 38 digit number. That’s smaller than a speck of dust. This brings a whole new set of problems as the antenna is so small that the range is only millimetres.

RFID tagged bees and RFID readers on a feeder

But an RFID chip that is about 2 mm2 is small enough to attach to the thorax of a bee and large enough to be relatively easy to detect … for example, when passing a reader at the hive entrance.

Flying home

How far do bees fly?

I’ve discussed this topic previously in a post titled Sphere of influence. Historically these studies were conducted by observing foraging activity in the badlands of Wyoming (where the bees had to fly miles to find anything), or by decoding the waggle dance to infer distances.

But let’s ask a slightly simpler question.

What is the furthest distance that a bee can successfully return to the hive from?

Just think about the practicalities of the experiment.

You could predict that the further away the bee starts, the less likely it would be to successfully return. In addition, the further away the start point, the longer it would take to return.

You’d therefore need to monitor lots of bees over a long time.

In addition, you’d need to be sure that the bees were not wind assisted, or – conversely – homing activity was similar irrespective of the direction the bee was initially transported.

So, more bees.

Time to chuck away those Posca pens and tag several hundred bees with RFID chips.

In 2011 Mario Pahl and colleagues did just that and published a study on the large scale homing of honey bees 9.

Like all good experiments, the study is elegant and relatively straightforward. The paper is Open Access if you want to read it yourself … or keep reading for the juicy bits.

The key experimental details

Recently returned pollen-laden foragers 10 were captured, tagged with an RFID chip ‘emitting’ a unique serial number, placed in a black box, transported up to 13 km from the hive and released.

The hive entrance was fitted with an RFID receiver and the exact time the bee returned – if she returned 🙁  – was recorded.

Map of the experimental area. Triangles mark release sites. Features discussed in text.

At least 20 bees were released in each of 33 different sites distributed to the north, south, east and west of the hive. The bees were transported to the release sites in black boxes so they could not get any positional information en route.

Anyone who transports bees (or cleared supers containing a few straggles) any distance will be familiar with their behaviour if/when you release escapees from the car. They spiral upwards in widening circles until they disappear from sight.

This is very similar to their behaviour on orientation flights. They are – literally – getting their bearings.

The ‘local’ landscape

It’s worth commenting here about the landscape features around the hive.

The experiment was conducted in Australia and the landscape around the hive was distinctive.

The hive was located 1 km east of Black Mountain (BM on the map above), 5 km north of Red Hill (RH 11 ) and about 4 km west of Mount Ainslie (MA). There was a lake (Lake Burley Griffin, LBG) immediately south of the hive 12.

Panoramic view of the experimental area from the home hive.

There was good forage in the immediate vicinity (within 500 m) of the hive, including the Canberra National Botanic Gardens. The authors therefore thought it “unlikely, but not impossible, that the bees knew the areas beyond the lake, behind BM and beyond MA”.

I counted them all out, and I counted them all back 13

Having released the bees they then decoded the unique tag numbers as the bees arrived back at the hive over the subsequent hours … and days.

The closer the release site, the more likely the bees were recorded returning to the hive. However, the homing rates – the percentage that returned for any given distance – were essentially the same for bees released to the north, south and west.

In these directions, no bees returned when released from much over 6 km distance.

Homing rates. The percentage of bees that successfully returned from distant release points.

In contrast, bees transported up to 11 km east of the hive managed to return successfully.

This was not due to the prevailing wind direction which was from the north-east and about 15 km/hr, and would have therefore probably aided bees initially transported north as well.

Flight speeds

The homing speed – assuming the bees flew in a straight line – was about 25 m/min for bees released to the north, south and west, but significantly higher (35 m/min) for the bees released to the east.

Of course, the bees probably didn’t fly in a straight line 14.

These speeds, when converted are only 1.5 – 2.1 km/hr. Honey bees can fly at up to 30 km/hr, but more typically fly at around half that speed.

At 15 km/hr all of the release sites were within an hour’s flight, indicating that a significant amount of time must have been spent searching for the correct bearing, rather than actually flying along that bearing.

The one exception to these flight times/speeds was for bees released on the opposite side of the lake. In this instance, flight times increased markedly despite the release sites being only 400 m apart. It is suggested that the bees minimised their flight over water by following the shoreline to the shortest crossing point in these instances.

Before moving on to the interpretation of the results it’s worth considering the numbers of bees studied, and the impossibility of doing this type of research without RFID technology.

1073 bees were tagged and released. Of these, a total of 394 returned (36%), though 75 of them (7% of released, 20% of returning) took more than 24 hours to find their way back to the hive.

Even the most dedicated PhD student would not be capable of doing this monitoring without the help of technology.

Why the longer and faster flights from the east? 

Considering it likely that the bees only knew the area within a couple of kilometres of the hive, how could they find their way back from up to 11 km away, an epic journey that took several days?

And why did bees initially transported east return at both a higher rate and a higher speed?

It seems likely that for the short to medium release distances (say <4 km), the bees used the distinctive shape of BH to guide them back to the hive. Since this mountain was immediately adjacent to the home apiary the bees would be familiar with it.

Alternatively, since bees are known to sometimes exploit particular flight lines based upon underlying landscape features, the global landmarks such as BM and MA could guide the bees to the next path segment of the flight line.

That wasn’t the question though … the question was why was it only bees flying from the east that successfully returned from distances up to 11 km away?

Getting their bearings

Bees released east of MA could not ‘see’ the hive-adjacent BM (as MA is in the way). However, the authors suggest that – by flying west towards a high point on the skyline (which initially happened to be the mountain MA) – the bees could then “continue on to BM”, where the familiar local features then lead them home.

Whilst that makes some sense to me, it also makes an assumption that the bees somehow fly up and over 15 MA to get a view of BM. Without that view, what else entices them to fly further west?

Do lots of the bees ‘lost’ returning from the east actually end up expiring during their futile search for a hive immediately to the east of MA? The fact that these successful long journeys took ‘several days’ (the precise times are not indicated for individual bees) indicates that the bees obviously spent a long time searching.

There’s an additional conclusion that can be reached from these long-distance journeys. Not only would time have been spent flying and searching, but the bees would also have had to make refuelling stops. A full crop of syrup is only sufficient to keep a bee flying for 25 minutes, or about 7 km at a typical flight speed of 15 km/hr 16. Therefore, the bees would have had to collect nectar several times on their journey.

So, what’s new?

In all honesty, not a lot.

The purpose of describing this study wasn’t because it unearthed some previously unknown details of the foraging or flight range of honey bees. Rather it was to introduce the concepts of uniquely tagged individual queen bees and using automated ‘readers’ to detect their movements.

It’s similar, but different, from the studies that involve uniquely barcoding bees I’ve described before.

Flight homing distances are considered a good indicator of the maximum potential foraging ranges. The figures determined using RFID-chipped honey bees are in broad agreement with the figures reported in previous analogue studies.

These place honey bees approximately mid-table in the league of ‘bee foraging distances’ … Ceratina smaragdula (a green metallic bee) goes no further than 200 m, whereas the South and Central American orchid bee Euplusia surinamensis boldly travels up to 23 km.

Some of the same authors applied this technique to investigate whether neonicotinoids were detrimental to the foraging behaviour of honey bees 17. At high, but sub-lethal concentrations, foraging activity was reduced and foraging flight times increased. However, at field-relevant nectar and pollen concentrations no adverse effects were observed. This study used RFID readers at both the hive and the feeder to record additional features of the foraging flight that would not have been possible manually.

You’ll realise, from the first full paragraph of this section, that I’d meant to discuss studies on queen bee (orientation and mating) flights. As tends to happen, I got a little distracted by espionage, the first electronic musical instrument, the names of mountains and Posca pens, so the queens will have to wait until another time.


 

Science snippets

Three short and easy-to-digest snippets of science this week. After last weeks’ overly-long DIY extravaganza I thought I’d try and be a little more succinct this time. 

The following triptych is based on three separate papers, two published in the last month or two and one from last year. Individually these incremental advances in our understanding probably do not justify a post of their own. 

The first paper, on sodium butyrate, was included here following a question I was asked during an evening talk to a beekeeping association last week. I don’t think I answered the question particularly well, so thought I’d elaborate here for clarity. The science is cool, but the paper is rather odd.

The other two papers are on a related topic, the bacteria in the gut of bees. The first of these came out last week and had a very catchy title. Reading that paper resulted in my burrowing back a year or two into the literature. While doing this I found a related paper that has got me thinking again about feeding winter bees honey, syrup or fondant.

Sodium butyrate reverses DWV-induced memory loss

All honey bees, perhaps with the exception of those in Australia 1, are infected with deformed wing virus (DWV). Historical studies that report 30% or 60% or whatever virus prevalence were probably using an insensitive assay. Even bees in Varroa-free regions carry DWV. 

And, in the absence of Varroa, DWV is not a problem to the bee 2. It is present at low levels and is apparently not pathogenic.

However, when transmitted by Varroa, the virus levels are amplified about a million times are a range of symptoms are clearly present. These include pupal death or the emergence of workers with overt developmental defects, including the classical ‘does what it says on the tin’ deformed wings.

DWV symptoms

DWV symptoms

In laboratory studies up to 70% of the bees exposed to high levels of virus exhibit these catastrophic symptoms.

However, some bees emerge with high levels of virus, but ‘look’ normal.

But they don’t behave normally.

In particular they have defects in memory and learning. 

Forgetfulness and getting lost

Impairments in memory and learning are bad news for bees. 

Foragers need to be able to learn where sources of nectar and pollen are by interpreting the waggle dance. Perhaps more importantly, they need to remember where the hive is so that they can successfully return from a foraging trip. If they forget where they are going, they’re doomed. 

A social insect like a honey bee cannot become a solitary bee without inevitably becoming a dead bee.

There is a long history of using sodium butyrate (NaB) to either enhance memory, or to reverse memory loss. It belongs to a class of compounds called HDACi’s (histone deacetylase inhibitors) which have been used in medical studies including anti-neural degeneration and anti-Alzheimer’s disease. 

NaB has even been used in studies with honey bees. In these it has been shown to enhance expression of genes involved in the immune response, detoxification and learning/memory. 

In addition, NaB restores learning ability in neonicotinoid-treated bees … it was therefore a logical extension (particularly since this neonic study was conducted by the same Taiwanese researchers) to investigate a role for NaB in counteracting DWV-induced learning and memory loss, the topic of the first paper this week 3 .

CCD and ‘massive disappearance’ of bees

This paper is a bit of a curate’s egg. The science is detailed and appears to be done well. The experiments are logical, mostly well-controlled and involve a combination of detailed molecular studies with monitoring bee behaviour in the field. 

However, the attempted link between memory loss and bee loss, the association with CCD (colony collapse disorder) and the superlatives in the paper make for a rather strange reading experience.

I’m not going to give a detailed account of the science. The key points are as follows:

  • NaB increased honey bee survival after oral DWV challenge 4. Disappointingly they did no virus assays.
  • NaB reversed memory loss in the standard proboscis extension assay (PER)
  • Gene expression studies indicated that NaB (an HDACi) resulted in increased expression of numerous genes, including reversing the suppression of some genes caused by DWV infection. Some of these genes were involved in memory, but many other gene classes were also differentially expressed. NaB was also shown to restore some neurotransmitter activity in the brain.
  • Colonies fed NaB and then fed DWV experienced a much reduced loss of bees than those that just received DWV.

Sodium butyrate reverses bee loss due to DWV (A) in/out ratios and (B) lost bee ratios

I need to re-read some of the methods and data on the in/out ratios (the graph on the left above) as it appears that more bees returned to the hive than left the hive! These field experiments used an automated hive monitoring system , but did not apparently use any form of tagging on the bees. It is not clear how they could be certain that the ‘returning’ bees originated from the monitored hive.

Smells fishy?

The conclusions of the paper end with the sentence a diet incorporating histone deacetylase inhibitors could be used to maintain the overall wellbeing of the bees and integrity of the colony”.

Well … perhaps.

I’d argue that prevention is always better than cure.

It is preferable to minimise DWV levels in the hive – by killing Varroa – than it is to try and counteract the deleterious effects of DWV by adding additional chemicals. Studies from my lab and others show that effective Varroa control results in very low virus levels.

But if you are going to feed them HDACi’s, then it probably should not be sodium butyrate. 

The ‘butyrate’ bit of the name is derived from butyrum meaning ‘butter’ in Latin. Sodium butyrate is a fatty acid and is famously smelly. It reeks of spoiled milk, or sour butter, and is the compound that gives vomit that distinctive ‘smell-it-a-mile-off’ odour.

Hmmmm …. nice 🙁

So, although it doesn’t smell fishy … it certainly does smell. 

Possibly not something you’d want anywhere near hives producing honey 😉

Chicken eating bees

I wrote recently about how important catchy titles are to scientific papers. The title of this next paper was the only thing that made me read the study …

Why Did the Bee Eat the Chicken? Symbiont Gain, Loss, and Retention in the Vulture Bee Microbiome by Figuerosa et al., (2021) mBio 12:e02317-21

How could you not want to read a paper with a title like that?

Well, one reason might be that you don’t know the words symbiont or microbiome.

Let’s see if we can change that … 😉

Vulture bees

Honey bees, along with all other bees, are classified with the sawflies, wasps and ants as members of the Hymenoptera. Of these, bees are wasps that switched to a vegetarian lifestyle, eating pollen and nectar.

Vulture bees dining out on chicken

However, some stingless bees also dine on carrion (literally ‘the decaying flesh of dead animals’) and a few species – the aptly named vulture bees – only feed on carrion for protein and no longer collect pollen.

You are what you eat

The microbiome is a collective term for the all the bacteria 5 in a particular environment.

For example, the gut microbiome or the skin microbiome. 

In the gut, these microbes help the host exploit novel food resources. For example, honey bees have bacteria (Gilliamella apicola) that help them digest toxic sugars 6.

The host (bee) benefits from the presence of the bacteria, and the bacteria benefits from the protection and food provided by the host … which is exactly what the term symbiotic means.

You are what you eat is, of course, not meant literally 7.

However, it is certainly true that the symbiotic microbiome is significantly influenced by diet. And the symbiotic microbiome also influences what can be consumed.

The Figuerosa et al., study compared the gut microbiome of a variety of stingless bees from Costa Rica. Some of these bees were pollenivorous and others were facultatively or obligately necrophagous.

Eh?

  • Pollenivorous – pollen eating
  • Facultatively – some of the time 
  • Obligately – all of the time / only
  • Necrophagous – feeding on corpses or carrion

The microbiome of vulture bees

By analysing the microbiome of these different types of bees the authors determined that reversion to a purely necrophagous lifestyle had resulted in the acquisition of a unique range of additional bacterial species.

Gut microbial communities in pollen-eating (absent), or facultatively or obligately necrophagous stingless bees.

However, the gut microbiome was not entirely unique. Many species were also found in facultative necrophagous bees, or in the pollenivorous species. 

It’s not yet clear what all these new species actually ‘do’ in the gut of these carrion eating ‘vulture’ bees. Further studies will be needed to determine this.

And, of course, this study begs the additional question.

Which came first, the chicken or the bacteria? 8

Did the microbiome change in response to a change in diet, or was the change in diet enabled by the change in the microbiome?

And, the topic of changes in the microbiome is the topic of the third paper … which, you’ll be relieved, is on honey bees.

The microbiome of summer and winter bees

I really used the ‘vulture bees’ paper to introduce the concept of the symbiotic microbiome.

In honey bees, the microbiome has been extensively studied over the last decade or so.

A striking feature is that it includes relatively few species of bacteria, and is dominated by less than 10 in total 9. These species are conserved regardless of geography, life stage (nurse bee, forager etc.) or season.

Almost every study of the honey bee microbiome has been a qualitative one. By that I mean the scientists determine the species present, but ignored the quantities of the different bacteria. 

In comparison, a quantitative study would have determined the amounts of some or all of the core species in the microbiome. 

And that is exactly what Kešnerová et al., (2020) did in their study entitled Gut microbiota structure differs between honeybees in winter and summer 10.

Multi-year, multi-hive studies

As you would expect from a paper in the ISME Journal 11 this is a thorough study, involving sampling of one hive on a monthly basis for 24 months, and fourteen hives in two different locations in the summer and winter. Each sampling involved multiple individual bees that were analysed. There are some additional experiments on colonisation of the gut that I’m going to largely ignore here.

The authors qualitatively and quantitatively studied only five of the core species and two non-core species from the gut microbiome. The names don’t really matter, but are shown in the figures below.

The gut microbial community differs between summer foragers and winter bees

There’s a huge amount of date in this figure.

However, simply by looking at the monthly changes (A), or the community composition (B), it is clear that summer foragers and winter bees have significantly different microbial populations within the gut.

In addition, the overall levels of many of the species tested (C) were significantly increased in the winter bees population.

Summer bees, nurse bees and winter bees

From a physiological and dietary point of view, there are some similarities between nurse bees and the long-lived winter bees. The authors therefore tested the bacterial population the gut of each contained in summer (foragers and nurse bees) and winter (winter bees).

Bacterial load and community composition in foragers, nurse and winter bees

Nurse bees and winter bees contained at least 10 times the population of bacteria as present in the gut of foragers (A, above). Of these, nurse bees were intermediate in the range of species between the foragers – which had a greater range – and the winter bees which contained fewer species.

Finally, detailed statistical analysis of the populations in the three bee types indicated that they were distinct (C), despite conservation of several of the core microbiome species. This latter analysis showed that, whilst each was distinct, all of the populations were similarly variable within a particular bee type i.e. none of the dots are more clustered/scattered in the third panel above.

Diet and the microbiome

Numerous studies have shown that diet influences the bacteria in the gut – of honey bees, vulture bees, flies, mice and men. It’s therefore very likely that the diet of nurse and winter bees at least partly accounts for the differences in the bacterial community present in their gut.

Foragers need an energy-rich diet and mainly feed on nectar and honey. In contrast, nurse bees and winter bees also consume pollen.

In studies I don’t have time to discuss, Kešnerová et al., (2020) also showed that feeding gnotobiotic bees 12 pollen and syrup resulted in significant increases in the amount and levels of bacterial colonisation i.e. they resembled nurse or winter bees. In contrast, bees fed syrup alone developed a gut microbiota that resembled that of foragers.

All of which made me think about feeding bees syrup/fondant for the winter vs. feeding/leaving them honey.

Honey is better for bees in the winter … really?

Beekeepers who leave their bees with a super or so of honey are often convinced of the benefits to the colony.

When pressed they unfortunately provide little evidence to support their expensive decision 13

I’m not aware of a single study that convincingly i.e. statistically, demonstrates that colonies are more successfully overwintered on a diet of pure honey, rather than a colony fed syrup or fondant. 

I’ve discussed this before – for example, see my response to this comment in the post entitled ‘Cut more losses’. 

Is the microbiome a marker of colony health?

However, this paper on the winter bee microbiome got me wondering whether – in the absence of evidence supporting better overwintering survival – bees fed syrup/fondant or honey have a different bacterial population.

It would be very interesting if they did.

Furthermore, as scientists further untangle the role of these bacteria, we would be able to tell whether syrup/fondant was better, worse or neutral in terms of the changes it induced in the bacteria that inhabit the winter bee gut.

Unfortunately, the Kešnerová et al., (2020) study has no details whatsoever of the hive management regime. The work was done in Lausanne, Switzerland, but it doesn’t say how or what they were fed for the winter.

Nor is there any mention of whether the diet was supplemented with sodium butyrate 14. This will also need to be studied as butyrate is a natural product of some gut microbes and there is evidence that – in humans at least – it is involved in communication between the gut and the brain.

And I think my gut is telling my brain that it would like some pizza …


 

Contact killer

As the days get shorter and the beekeeping season becomes just a fading (happy) memory, visitor numbers to this site start to dwindle. Still healthy 1, but perhaps only 30% of the numbers in May and June.

This is partly because there seems to be less to do at this time of the season.

No swarming, no queen rearing, no honey to harvest … and for many, no real thoughts of beekeeping.

It’s also undoubtedly because the voracious ‘read all you can’ beginners now have several months beekeeping experience.

Some are likely to think they know it all already 2.

Others may have given up in disgust when their colony swarmed (again) in August and they ended the season dispirited, queenless and honey-less 🙁

Of course, some beekeepers will be aware that, although there are some winter (or late autumn) tasks, there is no rush … there’s a whole winter ahead to deal with these and everything should then be fine until the season starts.

Au contraire as we used to say before Brexit 🙁

The paradox of timing miticide treatments

There remains one critically ‘time sensitive’ task to complete before the bees are ready for the season ahead.

Or, as I shall show shortly, not time sensitive with regard to the calendar, but time sensitive with regard to the state of the colony.

Not feeding … that should already be complete and they should not need topping up (if at all) until brood rearing really starts to ramp up in the early spring.

What needs to be done is to kill the mites – or as many as you can of them – that survive after the late summer/early autumn miticide treatment.

There’s an interesting paradox in miticide treatment …

The earlier you treat for mites once the summer honey has been removed, the more mites are present in the hive at the end of the calendar year. If you think about this – or look at my crudely drawn diagram 3 – it should be obvious why this is:

Mite numbers at the end of the year and the influence of early treatment

If you treat early enough (red line) to protect the winter bees from the ravages of Varroa and viruses, the mites that survive treatment will continue to reproduce in the small amount of brood reared at the end of the season (red arrow).

In contrast, if you treat too late to protect the winter bees (blue line), the surviving mites will have nowhere to reproduce as brood rearing will have stopped (blue arrow).

And there will be surviving mites.

None of the approved miticides 4 will kill more than 95% of mites in the hive 5.

Survivors

So, to start next season with the minimal mite load, you really need to kill as many of these surviving mites as possible.

The usual choice for a ‘midwinter’ mite treatment is oxalic acid. This can be trickled or vaporised and, under optimal conditions, kills 90-95% of the mites. You only need to administer it once and it is reasonably well tolerated by the bees 6

Let’s assume there are 200 mites remaining in your colony after the late summer miticide treatment and the last little flurry of mite hanky panky reproduction in the final round or two of brood reared by the colony.

If you can kill 90% of these mites with a single OA treatment there will only be 20 mites remaining at the beginning of the following season.

But can you kill 90% of them?

Oxalic acid is only effective against phoretic mites. Any mites lurking in capped brood cells will escape treatment. Therefore, if some, most or all of those 200 mites are in capped cells there will be significantly more remaining at the start of the following season.

During the active brood rearing season it has been determined that ~10% of mites are phoretic at any one time. Unfortunately, I’m not aware of any similar studies for the proportion of mites that are phoretic outside the spring and summer.

So, in the absence of any hard data let’s do some arbitrary arm waving calculations … 😉

The graph below shows the numbers of mites surviving a 90% 7 oxalic acid treatment where the percentage of phoretic mites ranges from 100% to 10% i.e. a range covering everything from a totally broodless colony to one with excess brood in all stages for the mites to parasitise.

Total mite numbers surviving OA treatment depends upon the proportion that are phoretic when treated

Unremarkably … the greater the percentage of mites that are phoretic, the fewer mites are left in the hive after the oxalic acid treatment.

And, equally unremarkably, for a contract contact killer 8 like oxalic acid, it is only when all the mites are phoretic that 90% of the original 200 mites can be killed. As you can see from the graph, if only 50% of the mites are phoretic, 55% of the total number of mites in the hive will survive treatment.

If you look at the 10% phoretic column you will understand why a single oxalic acid treatment in the height of the season – or for that matter dusting with icing sugar (which is even less effective) – has only a very limited impact on the overall mite numbers. If only 10% of the mites are phoretic then a whopping 91% of the mites (182) will survive.

Whopping?

Aren’t these are all quite small numbers?

20, 74, 146?

What’s a handful of mites between friends?

Does it really make a difference whether your hive contains 20 or 74 or 146 mites at the beginning of the following season?

Yes, it does.

It makes an enormous difference.

The mites present in early January will reproduce as brood rearing ramps up in spring. Therefore, at any particular time point in the season – assuming all other things are equal – there will be a significantly higher mite load in a colony that started the year with more mites, than one that started the year with fewer mites.

We know quite a bit about the reproduction of Varroa. For example, we know more progeny are reared when feasting on drone rather than worker pupae (because of the longer duration of pupation). There are a host of additional parameters that influence the reproduction rate of the mite population – the proportions of drone to worker brood, the availability of brood, the duration of the phoretic phase of the life cycle (in turn, likely influenced by the availability of suitably aged nurse bees) and so on …

All of which means that we can predict the number of mites present in a hive during the season based upon the number of mites at the start if we make a series of assumptions of hive strength, time of the season, rate of colony build up etc.

I used to use the BEEHAVE software to do this type of colony modelling. However, recent changes to the programming language 9) means BEEHAVE now barfs a slew of error messages back at me when I use it. Since I’m not keen to try and patch up something that is based on outdated or deprecated libraries I’ve instead been dabbling with Randy Oliver’s Varroa Model which is Excel-based.

Randy Oliver’s Varroa Model

Many of you will know Randy as a regular contributor to the American Bee Journal, a commercial beekeeper and the author of scientificbeekeeping.com.

Modelling mite numbers

Using this mite calculator you can easily predict how mite levels build up over the season.

Assuming there was an excess of brood available throughout the season (there isn’t as I shall explain shortly) you could expect mite numbers to increase 154-fold between January and September.

Unrestricted mite replication – the more you start with the (many) more you get

Therefore, if you started the season with just 20 mites there would be ~3000 in the hive by the time the colony is rearing the winter brood in September.

Conversely, 182 mites in January would multiply to over 28,000 by September 🙁

Of course, there is not an excess of brood available throughout the season. For example, in the early spring brood is limiting. However, we can factor brood availability by modifying the calculations to take account of colony strength and build up, reinfestation rates and the proportion of drone brood being reared in the hive.

All of which has conveniently been included in the Varroa Model … thanks Randy 🙂

Mite numbers in September predicted with Randy’s Varroa Model

These various limitations inevitably restrict mite reproduction and the fold-increase between January and September is ‘only’ about 100. This means that a colony that started the season with 20 mites will contain just over 2,000 by September, whereas a colony that started with 182 mites will end up with over 18,000 by the end of the summer.

18,000 is a lot less than 28,000 … but it’s still a humungous number of mites.

Or, more scientifically, it’s an infestation level that the colony is unlikely to survive. 18,000 mites is probably well over one mite for every two adult bees in the colony. With that level of mites you can expect every pupa to be parasitised.

The colony is doomed.

You can check these numbers if you want. The Varroa model is freely available from scientificbeekeeping.com and is well documented. I used V19 for the calculations above. I also used the model with almost all of the default settings unchanged 10 – specifically this was the colony type Randy designates ‘D’ meaning Default colony in temperate climate, managed to prevent swarming (slight fall brood buildup). The only change I made was to set mite immigration (drifting) to 0.

Are you now convinced of the need to treat in ‘midwinter’?

The ‘midwinter’ mite treatment needs to be applied to minimise the mite levels the colony starts the season with the following year.

However, to be maximally effective, this ‘midwinter’ treatment needs to be applied when all of the mites in the colony are phoretic. That means that winter oxalic acid trickling (or vaporisation) needs to be done when the colony is broodless.

Not when it’s convenient for the beekeeper because s/he is getting over an excess of mince pies and port in the now almost universal holidays between Christmas and New Year’s Day.

‘Midwinter’ is not in the middle of winter … beekeepers should (mis)use the term in the same way they (mis)use phoretici.e. not literally.

Brood rearing – if it ever stops (which I’ll return to at the end) – probably restarts around the winter solstice. That means that there will be sealed brood in the colony early in the New Year. I don’t know how much of that brood is likely to be infested, but I do know that any that is infested will inevitably mean that I’ll be killing fewer mites than I could … and therefore that I’ll be risking exposing the colony to much higher mite levels later in the season.

We’re now in mid-November. Almost all beekeepers should have completed their late summer miticide treatment by now. My Apivar strips were removed almost a month ago.

The precise timing of the ‘midwinter’ mite treatment is irrelevant as long as it coincides with a broodless period in the colony.

I therefore monitor brood production in my colony from late October onwards. As soon as the colonies are broodless I treat with oxalic acid.

There is nothing to be gained by waiting until later in the year. A phoretic mite is a phoretic mite … once they’re unable to hide away I’ve got a 95% chance of killing them.

Those are my sort of odds 😉

I’ve previously discussed how to monitor for a broodless period. If you don’t want to open the hive then learn how to read the debris on a Varroa tray. It’s not witchcraft or rocket science.

Biscuit coloured (or a bit darker) cappings indicating brood rearing in this colony

I expect my colonies to be broodless next week. It’s a little later than last season, but we had warm weather through much of the early autumn. If they’re not broodless yet I’ll hold off treatment for a fortnight or so. Past experience has taught me that the colonies (here in Scotland) are almost inevitably broodless for at least 2-3 weeks between late October and mid-December.

And, if your colonies are never broodless in the winter, all of the above still applies … except you have the slightly more difficult task of identifying when there is the minimal level of sealed brood in the colony.

Why the minimal level?

Because, unless there are weird things like multiple mites infesting each cell, it is logical to assume that when the brood level is at a minimum the phoretic mite level will be at a maximum.

Global warming

As we reach the end of a not-altogether-convincing COP26 conference I thought I’d also mention a recent paper by Giles Budge and colleagues in Newcastle.

I have found it is easier to manage mite infestation levels in Scotland than when I lived in the Midlands. I have a lot more flexibility in the timing of the winter treatment now as the colonies are broodless for longer.

With global warming we can expect warmer winters and therefore it’s probable that colonies may have sealed brood for more of the calendar year.

That will make mite management more difficult.

Certainly not impossible though … particularly if you learn now 😉


Notes

A major power outage has meant this was written by candlelight and hot-spotted mobile phone connection. Once power is restored I’ll go back and tidy some of the text and add the keywords. In the meantime I’ll fire up my trusty Ghillie kettle to make another brew 😉

Ghillie kettle

Socially distanced bees

A real skill when writing scientific papers 1 is to give them a suitable title.

Choosing the title involves a combination of art and science.

It must look appealing … you want the viewer to become a reader.

Since it is always indexed by search engines you must make sure it includes suitable keywords or phrases.

It needs to be informative. At least sufficiently so that the ‘take home message’ is clear. Even if the viewer does not become a reader they should still remember the title and so know the gist of what the article concludes.

The art of good title writing goes beyond this though. To increase the appeal, if it includes humour, some sort of half-hidden pun or some clever word play, then all the better.

And there are some great examples out there:

  • You probably think this paper’s about you: narcissists’ perceptions of their personality and reputation by Erika Carlson et al. (2011) in Journal of personality and social psychology 101:185-201. doi:10.1037/a0023781
  • Fifty ways to love your lever: Myosin Motors by Steven Block (1996) in Cell 87:151-157 https://doi.org/10.1016/S0092-8674(00)81332-X

There’s another variant of the latter and a host of additional variously funny or insensitive titles in this post on Slate. This also includes mention of the contrived efforts some scientists make to include Bob Dylan song titles in their publications (see Freewheelin’ scientists: citing Bob Dylan in the biomedical literature in the BMJ) as part of a long-running bet with colleagues.

Making it topical

Failing humour – and you could argue that some of the examples above 2 or linked are failing humour – a good way to get a paper some attention is to use a title that overtly hints at topicality.

In this regard, two papers caught my eye 3 this week:

The first of these is topical because travel restrictions to limit infectious disease transmission is a near-daily news item. However, it goes further than that in also including the Blofeld-like quote. The paper also has an entertaining abstract which finishes with the words We only live once, and sub-sections entitled The man with the golden gut: food safety and infections and The fly who loved me: arthropod-borne diseases. 

However, I’m not going to discuss the analysis of Bond’s hand-washing, potential Toxoplasmosis or the disturbingly high mortality rate of his sexual partners.

You’ve seen the film(s), now read the book paper 😉

Instead I’ll briefly focus on the second paper which managed to sneak ‘social distancing’ into the title, thereby ensuring it was picked up by almost every newspaper in the UK.

Socially distanced bees

‘Briefly’ because it’s a long paper and because rather too many of the figures are uninspiring bar charts like this one:

Spatial shift in allogrooming behaviour

… which, if you read the legend shows that there is almost no significant (ns) difference in allogrooming behaviour (which I’ll come to shortly) between Varroa-infested and -uninfested bees.

However, some of the graphs do have bars of different heights (and that are statistically significantly different) and there’s an interesting contradiction between studies conducted on full colonies and individual cohorts of bees.

So, rather than work through the entire paper I’m going to just focus on a few points and then discuss a couple of things that I found interesting.

Hypothesis driven science

Social insects, like ants and bees, are particularly at risk from pathogens and parasites. Their large populations, high density and ample food reserves means they have had to evolve both individual and social immunity.

The former prevents or mitigates infection of the individual, the latter reduces the chances that the colony will get infested (or restricts the impact of any infestation or infection to help ensure the survival of the colony).

The authors hypothesised that the presence of Varroa might induce some of these social immune responses. For example, bees might increase grooming activity in areas of the hive where Varroa were most frequent, or they might decrease antennation or trophallaxis with infested nest-mates, all to reduce the chance of mite transmission.

They focused on two particular aspects of social immunity and colony organisation, and made two predictions (hypotheses) for each:

  1. Space usage.
    1. Spatial shift of waggle dances to the periphery of the brood nest in infested colonies when compared with uninfested colonies.
    2. Spatial shift of grooming activity to the core of the colony in infested colonies when compared with uninfested colonies.
  2. Social behaviour.
    1. Infested bees would be expected to show changes in social behaviour including an increase in allogrooming, and decreases in antennation and trophallaxis.
    2. Changes in the structure of the social network in the infested hive, with decreases in connectivity and centrality.

Using colonies with high and low (almost negligible – I’ll return to this later) mite levels they then conducted observational science – they watched waggle dances, allogrooming etc. – to see if their predictions were correct.

Compartmentalisation of the colony 

When we open a hive all we often see is a mass of bees covering every frame.

Lots of bees

Beekeepers are often too busy trying to find the queen, or judge whether there are eggs or sufficient stores present, to appreciate that the bees are organised into two main ‘compartments’ within the colony:

  • an outer one occupied by foragers (the older bees) located nearer the hive entrance.
  • an inner one containing the young nurse bees and the queen, all of which are mainly arranged on brood.

The authors reasoned that since foragers represent a potential entry route of Varroa into the hive, you might expect the waggle dancing foragers to move the ‘dance floor’ to the periphery of the colony.

Does this make sense to you? To me it only really makes sense if you assume that the forager picks up a mite from elsewhere, for example when robbing a mite-infested collapsing colony elsewhere and returning to the hive. The alternative is that that forager was already carrying a mite, though I suppose that’s still a mite being introduced (or, more correctly, reintroduced) to the colony

Whatever the reason – and this wasn’t really elaborated – the changes in space usage and social behaviour would be expected to increase the compartmentalisation of infested colonies, so reducing mite spread.

Remember, mites predominantly associate with nurse bees and need to spend several days ‘surfing’ around the colony on these bees before entering a cell to reproduce.

Experimental details

Two month before the experiments started observation hives and other colonies were treated with dribbled oxalic acid. The colonies destined to be “Varroa-free” were then treated once a week for two further weeks with trickled oxalic acid.

Six weeks later, at the start of the observations, Varroa levels were strikingly different. The infested colonies were about ~6.2% and the “Varroa-free” uninfested colonies ~0.1%.

6% means six mites for every 100 bees sampled.

The team recorded the location of waggle dances and allogrooming in observation hives. Independently, using individually marked populations of caged bees, they recorded allogrooming, antennation and trophallaxis.

And, just so we all know what these terms mean:

  • allogrooming – is where one bee removes foreign particles and parasites from another bee
  • antennation – is how bees identify nestmates in the hive, by touching with the antenna
  • trophallaxis – is where one bee feeds another bee liquid food

Spatial shifts in waggle dancing and allogrooming

The colony is approximately spherical, sliced through by the vertically-hanging frames. The authors distinguished between the central frames and the lateral frames, and the position on the frames being closer or further away from the hive entrance 4.

In uninfested colonies the waggle dance and allogrooming activity occurred on both central and lateral frames, and predominantly on the lower half of the frame.

In contrast, infested colonies showed a significant shift of waggle dancing activity to lateral frames, and to positions closer to the hive entrance on these lateral frames. The allogrooming activity also shifted, but in the opposite direction, becoming concentrated on a larger area of the central frame.

These spatial changes were statistically significant and they should have the effect of keeping the forager and nurse bee populations better separated, and of concentrating the grooming activity to the centre of the colony.

Spatial organisation of nurse bees (yellow) and foragers (red) in mite-infested and uninfested colonies

Did the latter occur because that’s where most of the mites are located … hanging around waiting for a suitably-aged late stage larva to snuggle up with?

Or, does allogrooming become concentrated in the core because the nurse bees – which are responsible for most allogrooming activity – have relocated from other areas within the colony?

Or both? … these are not mutually exclusive.

The diagram above is my half-assed rather poor attempt to demonstrate the changes in compartmentalisation within the colony. In the colony on the left there is much more mixing and overlap between the nurse and forager bees. On the right there is much less mixing, and therefore less opportunities for mite transmission.

Social behaviour

The studies on social behaviour were somewhat less definitive, or produced unexpected results. These studies were all done using caged bees from infested or uninfested colonies. Allogrooming, antennation and trophallaxis can all be divided into ‘giving’ and ‘receiving’ activity, all of which was recorded, as was whether the bee from the infested colony was activity carrying a mite.

The expectation was that these activities – all of which are likely to increase the opportunities for mite transmission – might all be reduced in bees from Varroa-infested colonies, with one or two caveats.

In fact, in the majority of cases there were no significant differences between the levels of allogrooming, antennation and trophallaxis.

The exceptions included Varroa-parasitised bees which were – perhaps understandably – more likely to be the recipients of grooming.

Infested colonies overall exhibited slightly increased antennation, with Varroa-carrying bees receiving significantly more attention from cage-mates and – in turn – performing less antennation.

Finally, although there was no overall difference between trophallaxis between bees from infested and uninfested colonies, bees actively parasitised by Varroa received more trophallaxis … an unexpected result considering the potential for mite spread.

The final hypothesis that was tested was whether the social network changed in infested colonies. This was based upon analysis of high resolution videos of caged bees, recording the interactions between and then calculating the connectivity and centrality of the network.

I’m deliberately being brief in my description of the methodology here, for two reasons; 1) it’s complicated and would take 500 words to describe more fully, and 2) there were no differences in the measured parameters of the social network in the infested bees when compared with the bees from the uninfested colonies.

Contradictions

Looking back at the predictions (see above) it seems clear that there were large scale changes in space usage within the colony … perhaps justifying the phrase ‘social distancing’ in the title.

However, when the authors looked at individual cohorts of bees they did not detect evidence of increased small scale separation – either within the social network they formed, or in terms of avoiding activities that would be expected to lead to mite transmission.

In fact, the caged bees showed increases in activities that were commensurate with ‘care giving’ … increased grooming and trophallaxis of Varroa-carrying individuals.

These appear to be contradictory observations.

How can the large scale spatial reorganisation occur without changes in the bee-to-bee interaction that occurs at a smaller scale?

The authors skirt around this a little, but don’t really tackle it head on.

Loose ends

I think a couple of things warrant further investigation.

The large scale spatial reorganisation was of activities (dancing and grooming) not of bees, though there was an unwritten assumption that the activities were observed to move because they were conducted by particular ages of bees (which did move).

That could be tested by high resolution video observations of a colony containing marked cohorts of nurse bees and foragers. The expectation would be that – like the red and yellow circles I’ve drawn above – you would expect to see a more distinct separation of the two groups.

With sufficient time, money and video recording you could also use this in place of the studies of small cohorts of caged bees. For example, using lots of bar coded bees. Perhaps these don’t perform in the same way outside the hive as inside it?

Oxalic acid treatment

The authors used oxalic acid to reduce mite levels in the “Varroa-free” hives.

Unusually – at least in my experience – they used three weekly treatments of trickled oxalic acid.

This seems to have been very effective in reducing mite levels – compare the 3 x treated (0.1% infestation) to the 1 x treated (>6% infestation) – five to eight weeks respectively after the treatment started.

I was surprised it was that effective in a colony that was activity rearing brood, where the majority of the mites would be hidden in capped cells.

However, there are numerous studies that show that trickled/dribbled oxalic acid damages open brood 5. Therefore, in the studies conducted in this social distancing paper there’s a possibility that an entire generation of brood were missing due to the three successive treatments with trickled oxalic acid.

How this would have affected the results is unclear.

Although bees display temporal polyethism they also exhibit developmental plasticity and can change roles if and when needed. This doesn’t appear to have been considered and is certainly not discussed in the paper.

How is social distancing achieved?

But, let’s take their clever and topical title at face value and accept that bees do socially distance in response to mite infestation 6.

What level of mite infestation is needed to initiate this activity?

What are the molecular (chemical) or behavioural signals that trigger this activity?

Can we, as beekeepers, exploit them to improve the efficacy of rational mite management?

All of which will involve wild speculation and precious few hard facts, so I’ll save it for another time 😉


 

Autumn cleaning

Over the last fortnight, despite some occasional warm and sunny days, the autumn has made its presence known. 

Flaming autumn aspen

The aspen down the road are a stunning colour at this time of the year. Although I’ve planted a couple of dozen, they’re still not more than thigh-high and it will be quite a few years until they can match the display shown above.

Almost overnight hundreds of redwing have arrived from Scandinavia and many of the rowan have already been stripped bare 1.

In Fife, the leaden skies are filled with skeins of geese forming raggedy V’s as they fly in from the North Sea. It’s an evocative sight … it reminds me of my first weeks as an undergraduate student at Dundee University half a lifetime ago

And it also emphasises that the beekeeping season is over.

Of course, there will be jobs to do in the winter, but the bees are pretty much on their own for at least the next five months.

Apivar

The final essential task of the season for me is to remove the Apivar strips that went into the hives in August. Initially the strips were placed on either side of the – still large – brood nest. A few weeks ago I removed the strips, scraped them free of propolis and wax and re-inserted them around the, now shrunken, brood nest.

Mid-autumn and time for the Apivar strips to be removed

You can just about see them in the photo above, flanking the four central frames.

It is important to remove the strips. Although Apivar has a relatively short half-life, some residual activity will remain. If you leave them in the hive any surviving Varroa – and there will be survivors 2 – will continue to reproduce in the presence of trace levels of amitraz, the active ingredient in Apivar. 

With reduced – and possibly borderline for killing – levels of amitraz present, these are ideal conditions in which resistance may develop. Although this has been reported it does not appear to be widespread. 

Therefore, to ensure that Apivar remains an effective miticide it is important to remove any remaining strips before the winter.

Your next adventure in Glenrothes awaits!

Tragic isn’t it?

That’s the subject line on the emails I receive from Travelodge where I stay when I’m doing my beekeeping in Fife. 

Have you ever been to Glenrothes?

‘Adventure’ isn’t the word most people associate with Glenrothes. 

Good morning Glenrothes

GetMeOuttaHere is. 

This is a town where every third car being driven late at night has a raucous exhaust, lowered shocks, tinted windows and a spoiler. The drive-in queue for McDonald’s sounds like the pit lane at the Indianapolis 500 and there are more donuts in the car park than in the fast food outlets 3.

But none of that usually bothers me as, by the time I get to the hotel, I’ll have been driving for 5 hours and will have spent about the same amount of time inspecting colonies or lifting cleared supers. I may also have squeezed in a couple of hours of meetings at work.

The environment might be noisy, but the beds are comfortable. 

But visits in late autumn are a bit different.

No colonies to inspect, no grafting to do, no nucs to check for mated queens and no supers to remove.

All I need to do is gently lift a few crownboards and pull out the Apivar strips now that treatment is complete.

So, what do I do for the rest of the day?

Long range weather forecasting

Is that an oxymoron?

I book my trips to Fife to fit in with what the bees need. To make the hotel affordable I book many weeks in advance.

I therefore put up with whatever the weather throws at me. Usually it works out OK.

Furthermore, as regular reader know, several hives are in a bee shed, so the weather is largely irrelevant.

But ~60% of them are outside.

And Monday was really wet. 

Having driven for four hours through increasingly heavy rain – stopping en route to make a honey delivery – I fortified myself with a cappuccino and excellent almond croissant from Taste, the best independent coffee shop in St Andrews 4.

Essential fortifications

I then sat in the shed enjoying my late breakfast listening to the rain hammering on the roof.

I needed something to occupy me until either:

  • the rain stopped
  • it got so late in the day that I’d just have to open the hives and remove the strips anyway

And the obvious thing to do was a bit of spring autumn cleaning. 

During the season the bee shed is used on a daily or weekly basis depending upon the experiments underway. In addition, we have a storage shed on the same site and a number of additional hives in the same apiary. I also do most of my queen rearing in this apiary (the bee shed provides a near-perfect environment for grafting), distributing the nucs to other apiaries for mating.

And all that beekeeping tends to leave a bit of a mess. At least, it does where I’m involved.

Super job

For the last couple of years I’ve not bothered returning the extracted supers to the hives for the bees to recover the last of the honey.

Instead I’ve just stacked them ‘wet’ in the shed, protected from wasps, mice and robbing bees, by covering the top of the stack with a well-fitting roof.

Or a snug-fitting crownboard and a badly fitting roof.

Stacked ‘wet’ supers

Experience has taught me that the floor of the shed isn’t level and/or has gaps between the planking. Rather than seal all these gaps I simply stand the stack of boxes on the sort of closed cell foam sheeting used for packing furniture, or – when I run out – on double thicknesses of cardboard 5. This stops the wasps, ants and bees from getting access. 

So I started by tidying the stacks of supers. Inevitably this necessitated moving them first, sweeping the floor clean, laying out the foam/cardboard and then restacking them. There’s not enough space in the shed to move ~60 supers so they went out in the rain.

So I got wet 🙁

Floors, roofs, boards, unidentifiable objects and wax moth

Once they were back I could turn my attention to the other side of the storage shed which houses spare roofs, nuc feeders, floors, boards (split, crown, surf, Morris, Snelgrove etc. 6 ), a breeding colony of queen excluders 7 and a motley collection of other items that:

  • might come in useful
  • don’t logically belong anywhere else
  • appear valuable and/or difficult to make … but I don’t know what they are
  • are essential and were needed several times in the season … but I’d lost them 🙁

Sorting this lot out took another hour or two, and involved a further soaking as I needed to clear the space before I could refill the space.

Early on in the process … 

Is beekeeping the largest volume hobby?

… and when at least partial order had been restored …

Floors from Abelo, Pete Little and some homemade abominations

I also found several brood boxes full of drawn comb or sealed stores.

Excellent 🙂

And I found a nuc box lurking in the far corner containing comb riddled with wax moth 🙁

Wax moth larvae and damage

Aargh!

DiPel DF

Wax moth are something I’ve largely avoided or ignored for most of the last decade. The cold winters in Scotland seem to keep their numbers down.

Not this time … 

All of the infested frames were bagged up for burning at the earliest opportunity. The remaining brood frames were treated with DiPel DF, a suspension of Bacillus thuringiensis kustaki spores and toxins. If ingested by the larvae of wax moths, the δ-endotoxin component dissolves in the alkaline environment of the gut, is activated following cleavage by gut proteases and then ‘punches’ a hole through the gut wall.

Ouch.

And the spores germinate, allowing the bacteria to grow inside the larva.

As I wrote in a post several years ago about this treatment:

This isn’t good for the moth larva. Not good at all. Actually, it’s probably a rather grisly end for the moth but, having seen the damage they can do to stored comb, my sympathy is rather limited.

DiPel DF is non-toxic for bees.

DiPel DF

I’ve not had problems with wax moth infesting supers stored ‘wet’ … they’re after the old cocoons and other rubbish that accumulates in brood frames.

Vita used to sell a product called B401 – also a suspension of Bacillus thuringiensis spores and proteins – which was withdrawn from sale in 2019. Despite assurances that a replacement – imaginatively labelled B402 – would be available ‘soon’ it appears to only currently be sold in the US.

Out with the old … and the not fit for purpose

I was on a roll … 

All this organisation meant I discovered things that I’d lost … like a small stack of contact feeders hiding in the corner that had not been used this season as I hadn’t done any shook swarms.

There they are! Contact feeders lurking shyly in the furthest corner (unlike those brazen frame feeders at the front)

I also found some mini-nucs I’d built for queen mating almost 10 years ago. They were made of ply and housed a tri-fold full-size brood frame (you can now buy these, but couldn’t when I built them). 

Tri-fold brood frame

However, the ply was starting to delaminate and it was pretty clear that they wouldn’t survive a Scottish summer season so they were unceremoniously binned.

And I finally bit the bullet and got rid of all my XP Plus queen excluders. These were bought from Thorne’s a few years ago and had been used only when I ran out of everything else.

In principle they are a good idea. A white plastic queen excluder with bee space on the underside provided by a raised rim and a series of small X-shaped spacers that stand on the top bars.

XP Plus queen excluder (the plus must mean ‘plus warp’)

However, in practice, they’re rubbish. They were the ‘ugly’ in my 2017 description of queen excluders that included the phrase ‘the good, the bad and the ugly’.  

They warp really badly. The photo above – if anything – obscures the warp because the QE is not being held flat. When you place them under a super the centre bows up and contacts the underside of the super frames.

Rubbish. 

Out they went.

The little things

There’s something rather poignant about the death throes of the beekeeping season. It can end with a bang as autumn storms roll in, or it can end in a protracted stutter as intermittent good days allow the bees to forage late into October. 

Of course, it’s au revoir 8 and not a final goodbye

It forms such a large part of my life for six months of the year that little things found during the clear-out bring back a flood of memories …

Nicot cup and (partly squidged) queen cell amongst the debris on the shed floor

A Nicot cup and vacated queen cell reminded me what a good queen rearing season we’d had on the east coast. Although the first round of grafting was a near-total failure, successive rounds were excellent, and queen mating was very successful. One of the best seasons in memory 9.

Coffee stirrer … or AFB test kit

Not all the memories were good ones though. I received one of the dreaded ‘AFB alert’ warnings for the apiary and spent a very long couple of days checking every cell on every brood frame in every colony, and testing any that looked suspicious.

I don’t take sugar, and the coffee stirrer shown above is provided in the AFB LFD kit to lift the dodgy-looking larva into a tube for analysis. Everything looked clear, but it gave me a few very stressful days.

And … after all that tidying, and repeated trips to the industrial-scale bins, it finally stopped raining.

Finally … some practical beekeeping

I fired up the smoker and quickly, but gently, removed all the Apivar strips. The crownboards on all the hives were very firmly stuck down with propolis and the bees, although calm, weren’t exactly overjoyed to see me.

Autumn still life – smoker, hive tool, Varroa trays and Apivar strips

I still had another apiary to visit. With rain threatening there wasn’t time to monitor the level of brood present so I slipped cleaned Varroa trays under the hives. This will allow me to inspect both residual mite drop and look for the presence of the characteristic biscuit-coloured cappings when brood is uncapped.

And then, after about half an hour of practical beekeeping, I set off back to the west coast as the rain started again.

The Moidart hills – An Stac, Rois-Bheinn and Sgùrr na Ba Glaise

Two days later the Moidart hills had their first dusting of snow.

It’s official, autumn is here and the beekeeping season is over.


 

Dancing in the City

Beekeeping is an increasingly popular pastime. Since ~84% of the UK population live in urban areas (up from ~70% in 1950’s) it is not unsurprising that the number of hives kept in cities is increasing.

Of course, not everyone who lives in a town or city keeps their bees in the back garden. When I lived in the Midlands I lived on a small estate that was indisputably ‘urban’, although there was farmland within sight 1. My bees were on the nearby farmland and I just kept a few mating nucs and a bait hive in the back garden 2

Hive in a field margin

I kept my bees in the farmland because 3 I reasoned that there were both larger amounts and a greater range of forage available for them there.

But I was probably wrong.

It wouldn’t be the first time, and it certainly won’t be the last.

Too many bees?

Before discussing urban bees and forage in more detail I’ll digress a minute to mention the suggestions that the inexorable rise and rise of urban beekeeping is threatening our native pollinators.

Actually … more than suggestions.

There are a number of scientific reports and reviews that indicate that urban beekeeping harms – by outcompeting – native pollinators like solitary bees. A recent report by the Royal Botanic Gardens at Kew states:

‘Campaigns encouraging people to save bees have resulted in an unsustainable proliferation in urban beekeeping. This approach only saves one species of bee, the honeybee, with no regard for how honeybees interact with other, native species.’

‘In some places, such as London, so many people have established urban hives that the honeybee populations are threatening other bee species.’

Our bees (Apis mellifera) are generalists. They are not particularly well adapted to any flower or nectar/pollen source.

They are equal opportunists.

Individually, there are many solitary bee species or non-hymenopteran pollinators, that are ‘better’ adapted. They pollinate more efficiently, or collect more nectar, faster.

But honey bees arrive in the environment mob handed.

Thousands of them.

Actually, tens or hundreds of thousands of them if there are several hives in an apiary. They are a formidable force and can easily outcompete other pollinators that are either solitary or only live in small colonies.

Save the bees, save humanity

When you see the phrase “Save the bees” what it usually means is save the honey bees.

Save the bees ...

Save the bees …

What it should be encouraging is “Save anything but the honey bees, because they don’t need saving … actually, there are possibly too many of them altogether”.

But that’s a lot less catchy … and it won’t let the supermarket, or food manufacturer or whatever, illustrate their campaign with cute photos of pollen-laden honey bees returning to quaint white-painted WBC hives in some sort of idyllic rural scene 4.

I suppose a photo of a honey bee would be better than drawing of a wasp though … which is what the NRDC used for a (mis)information campaign on CCD (colony collapse disorder) a few years ago.

D’oh!

Anyway … saving the bees is usually “greenwash” or bee-washing as it was termed by MacIvor and Packer in a 2015 paper on bee hotels 5

I’ll return to this topic, and urban beekeeping, later in the winter 6.

The Town mouse bees and the Country mouse bees

Where was I?

Oh yes, my – as will shortly be clear – incorrect assumption that country bees have access to more diverse and richer sources of forage than their poor relatives living in the town.

There are many sorts of countryside and many sorts of urban environments.

A hive in an intensively farmed arable landscape could be located in hundreds of acres of wheat fields, where all of the hedgerows were grubbed up years ago and replaced – if they weren’t just removed altogether – with barbed wire 7

How different is that environment to the ‘concrete jungle’ of a modern city? 

Tokyo

Surely that must be a terrible environment for bees?

In contrast, the suburban sprawl that surrounds most cities is possibly a good place for bees to live. Lots of neat little gardens, each 8 with a profusion of flowering plants, each chosen to provide vibrant colour for a much longer period than native plants.

And I’m sure we can all think of forage-rich rural environments. Here the bees gorge on early crocus, then gorse, willow, oil seed rape, clover, lime, blackberry, fireweed and himalayan balsam, before finishing the season will full crops and corbiculae from the ivy.

Now, in a recent publication 9 scientists have compared the forage available to town and country bees, and the results are quite surprising.

Let the bees tell you

If you live in a country with enlightened right to roam laws (like Scotland) you could wander around the countryside recording all the forage available to bees.

But the laws in England are much less enlightened. However, your right to roam in either country does not extend to the land around a private house or building. 

So, although you might be able to determine the forage available in the Scottish countryside, you can’t be certain you would have good enough access to do the same in England. And in a city you could only map what forage was available by peering over fences from public roads. 

So Elli Leadbetter and colleagues let the bees do the work.

They established 20 observation hives. Ten were in the the centre of London and 10 in agricultural land to the North East and South West of London. The hives were 5 km from each other to avoid overlapping areas of forage. They used observation hives so that they could watch and record the waggle dances of foragers in the hives.

I’ve discussed the waggle dance before. It is used to communicate three important pieces of information about a forage source:

  • direction
  • distance
  • quality

The first two bits of information are encoded in the angle of the waggle run to the perpendicular and the duration of the waggle run. The quality is conveyed by the number of circuits a dancing working performs. It’s a case of ‘the more, the better’ … energetically higher quality resources 10 result in more circuits.

Having recorded thousands of these waggle dances, they used the direction and distance information to ‘map’ where the bees were foraging.

GIS data, land use and foraging bees

For many locations there exists a wealth of land use data (GIS data; Geographic Information Systems). Much of this is at high resolution. For each of the 20 observation hives they produced a map of land use within 2.5 km of the hive at a resolution of 25 m. 

Land use was defined in broad categories such as 11 buildings, woodland, arable, pasture, fruit, OSR (all in agricultural areas) and dense or sparse residential, parks, amenity grassland or railways (all in urban landscapes). 

They then used some clever mathematics to decode the waggle dances 12 to work out where the bees had been, converting the distance and direction components to geographic locations.

Urban (top) and rural foraging heat maps, overlaid on GIS land use maps (5 km diameter)

These locations were overlaid on the land use maps to produce ‘heat maps’ showing where the bees were foraging. The image above shows these heat maps. In the spring the urban bees (top left) were foraging intensively to the east and west of the hive and the rural bees (bottom left) were mainly foraging in two large areas to the south east and south west of the hive.

Foraging distance and nectar quality

Even a cursory look at the image above shows that the urban bees tended to forage closer to the hive than the rural bees. But remember, that’s just three snapshots during the season.

Waggle run duration – rural bees fly further

However, more detailed analysis confirmed that this was the case. Throughout the season, the bees in the agricultural landscape foraged further from the hive. I’m showing the log-transformed median waggle run duration (above) as this allows slightly easier comparison across the season. The further the wiggly ‘best fit’ line is above the horizontal axis, the longer the duration of the waggle dance run, and so the further the bees are flying to find the forage.

Interestingly, the median foraging distances were relatively short when compared with the maximum foraging distances from the decoded waggle dances. This applied wherever the bees lived. For urban bees the median was 492 m (max 9375 m) and for agricultural bees it was 743 m (max 8158 m 13 ).

Perhaps the agricultural bees were flying further because there was better quality nectar available at more distant sites?

Nectar concentration (% w/w) sampled from returning workers

They controlled for this by recovering returning foragers and robbing them of their nectar load before analysing the sugar content. There was no significant difference 14 between the nectar from agricultural or urban landscapes. The sugar content of the nectar was recorded as reducing through the season.

Foraging preferences

So where did the town bees and the country bees prefer to forage?

City rooftop bees

City rooftop bees …

In urban areas the bees exhibited a strong preference for residential gardens (the ‘sparse residential land’) … these are presumably the flower-rich urban gardens that the homeowners also tend to prefer.

In contrast, bees in an agricultural landscape showed an entirely unsurprising reliance upon mass-flowering crops like oil seed rape (in spring only). They also showed weaker preferences for arable land and fruit crops throughout the season.

Mid-April in the apiary ...

Mid-April in a Warwickshire apiary …

I’ve skipped over a host of additional observations from the study, and almost all of the controls. Two things that are worth mentioning though.

Firstly, hive strength had no influence on waggle dance duration (and hence foraging distance). It therefore wasn’t the case that stronger hives had a larger workforce that could survey and exploit more distant forage. 

Secondly, cities are warmer due to the urban heat island effect. However, temperature also did not affect waggle dance duration when it was factored in. So, the city bees aren’t foraging at shorter distances because the dance is truncated at higher temperatures.

Conclusions

So, although cities are predominantly filled with buildings and roads, city bees travel less far to forage when compared to bees in agricultural landscapes.

This strongly suggests that the urban landscape consistently provided more available forage 15

Conversely, the bees in agricultural landscapes had to fly further, not because there were better quality nectar sources available at long-range, but because there wasn’t enough nectar nearby.

There were a number of additional interesting points in the paper, some of which were known already from other studies. For example, the high sugar content in spring nectar was already known (and confirmed here). Similarly, foraging distances in midsummer were longer than those in spring or autumn. This could be predicted due to the reduced rainfall in summer, and consequently the reduced overall level of nectar available.

I need to think more about how this study contributes – if at all – to the ‘too many bees in cities’ argument. If anything, forage-rich towns should be able to support a greater number of bees 16 without the honey bees impacting on other species. In contrast, honey bees in agricultural landscapes might dominate the available nectar sources because they can forage at long distances and then communicate to their nestmates the location.

Perhaps it just shows that that heavily farmed land is actually very poor in terms of nectar availability? It’s either boom or bust … once the OSR has finished, or the clover has been ploughed in, or the fruit trees stop flowering then there’s nothing left 🙁

It would be interesting to conduct a similar study in a forage-rich, non-agricultural, rural landscape.

Access all areas

Finally, I think a particularly neat thing about this study is the use of bees to ‘map’ the forage availability using what the authors term “a large-scale search effort that has no access limitations”. The scientists interpreted the waggle dance to get information that would otherwise have been difficult or impossible to determine.

However, using the bee’s own perception of the distances flown might actually lead to inaccuracies in the calculations. As discussed previously, bees measure distance by optic flow. Optic flow increases in complex landscapes … and cities are likely (at least to us, and certainly when compared with arable farmland, to bees) to be complex landscapes. Increased optic flow leads to a perception of increased distance, and hence to longer waggle runs.

This means that bees in complex landscapes might overestimate the distance they have actually flown to forage. Conversely, those in uniform landscapes might underestimate.

Which means that the results of this study may be a conservative estimate of the differences in foraging distance.

And therefore a conservative estimate of the differences in forage availability in urban and agricultural landscapes.


Notes

Dancing in the City was a pretty cheesy song that reached #3 in the charts for the rock-pop duo Marshall Hain in 1978. Having remembered the track when thinking up a title for this post, I made the mistake of listening to it on Spotify.

I now can’t get the damned thing out of my head. 

But it gets worse. I rummaged through Wikipedia and discovered that Kit Hain, the vocalist, subsequently had a very successful songwriting career with people like Roger Daltrey, Chaka Khan and Fleetwood Mac. Impressive. 

In contrast, Julian Marshall, the keyboard player became a member of the Flying Lizards who had a minor hit with a cover version of Barrett Strong’s 17 Money (That’s What I Want)

… and now I can’t get that out of my head 🙁