Category Archives: Bees

The million drones fiasco

Accidents happen.

Sometimes they are due to stupidity, sometimes to forgetfulness, or sometimes they are just the result of plain dumb luck.

They’re also often caused or at least exacerbated by ‘local’ factors – like a rainstorm or a cancelled train preventing timely inspections.¬†

Or a countrywide lockdown necessitated by a global viral pandemic.

With the exception of the cancelled train my excuse for what follows is “all of the above” ūüėČ

Social distancing

Beekeeping, like other activities involving livestock management, has been a permitted activity during lockdown. Beekeepers have been allowed to travel to their apiaries and to move bees for pollination etc. 

I was away when lockdown was imposed and opted 1 to stay where I was. For the first half of the season I’ve had to forego weekly colony inspections. I’ve not had the pleasure of watching the colonies build up, of queen rearing or of sweating profusely when shifting nectar-filled supers ūüôĀ

Instead all my beekeeping – the first inspection of the season, the swarm prevention and the swarm control – have been squeezed into two visits, each of a few frantically busy days, in late April and mid-May.

And, inevitably, mistakes have been made.

Well, one mistake … that I’m currently aware of.

First inspections and swarm prevention

We’re late starters in Fife.

It’s not unusual to delay the full first inspection until the very end of April in this part of Scotland. A couple of years ago we had knee-high oil seed rape (OSR) ankle deep in snow at the end of April.

There seems little point in disturbing the colony if it’s too cold to have a leisurely look through the brood box. The bees get tetchy, the brood gets chilled and you don’t have time to look for the important things – like disease, or that elusive queen you failed to mark last autumn.

However, this season started well and I should have started colony inspections in the second week of April.

But by that time the world had changed dramatically …

I finally snatched a couple of days around the 25th of April to do the first inspections and swarm prevention all rolled into one … and coupled this with reducing my colony numbers by 50% to make management over the coming months easier 2.

I’ll discuss how I did all this in a couple of full-on days some other time. The end result was about a dozen united colonies, each topped with three supers, containing a good marked laying queen. Many of the colonies were very strong, with up to 15 frames of brood after uniting 3.

The colonies were strong and healthy. All were headed by a laying queen. I saw all but a couple of the queens 4 and clipped and marked all those I found that weren’t already 5.

Safely back in the hive

Three supers were overkill for the usual spring nectar flow. However, there was already a reasonable flow on and I wanted to give the colonies a good amount of space in the hope of delaying swarm preparations. 

Swarm control

Colonies usually start making clear their intent to swarm in the second half of May here. It varies a bit depending upon how advanced or otherwise the season is – one of those unknown knowns.

I kept in email contact with beekeeping friends about their own colony build up. By the time I received the first email saying charged queen cells were present (~16th of May) I was travelling back to do my own swarm control.

I decided to use the nucleus method whether queen cells were present on not.

Effectively I was going to implement¬†preemptive swarm control on some colonies. By taking the queen out into a nuc the colonies would be forced to requeen, I’d then leave a single charged/capped queen cell and let them get on with it.

All looking good …

And for eleven of the colonies that’s precisely what happened.¬†

I removed the queen on a frame of emerging brood and shook some of the bees from a second frame into the nuc box. These were to be relatively small nucs but made sure each had a full frame of capped stores (saved from colonies at the first inspection). I also added a frame of drawn comb and two foundationless frames.

I sealed the nucs and moved them to another apiary.

Three of many … and hive number 29

Most of the brood boxes had play cups with eggs and about 50% had charged queen cells. There were no capped cells. I marked frames containing promising looking charged cells and closed the boxes up.

… and still looking good six days later

Six 6 days later I went carefully through every frame in the de-queened colonies.

One good queen cell, an old play cup and some rather old comb

All the boxes had good looking queen cells and I made sure I left just one in each colony. 

The nucs also all looked great when I checked them on the same day. 

New comb with queen already laying it up

The queens were laying well and the bees were drawing new comb. They would be fine for another few weeks. 

Come in Number 29, your time is up

One of the colonies proved more problematic.

Hive #29 … this had been left as a strong single brood colony on the 25th¬†of April.

Three weeks later it was – unsurprisingly – still a strong single brood colony. The bees were busy and the supers were already filling nicely 7.

What was missing from the brood box in mid-May were eggs, larvae or capped brood ūüôĀ

Had I inadvertently killed the queen 8 at the last inspection? The 21-22 day interval would have meant that all worker brood would have matured and subsequently emerged 9.

However, the temperament of the colony suggested it wasn’t queenless. The bees were calm, they were foraging well and bringing in good amounts of OSR pollen.

With a sense of dread I had a look in the supers …

Let there be drones

About 75% of my many super frames are drawn on drone cell foundation. For the same amount of wax – by weight – you store more honey. I also think there may be advantages when spinning it out in terms of honey recovery 10.

In addition, if you use drone cell comb immediately over the brood box, you dissuade a strong colony from storing an arch of pollen over the brood nest in the super …¬†

Drone comb in super

… though they do often leave cells empty, ready for the queen to lay.

But she can’t do that because she’s trapped under the queen excluder.¬†

Right?

Wrong ūüôĀ

The middle few frames of the lower couple of supers were wall to wall capped drone brood and drone larvae. The queen was busy laying up some of the remaining space that wasn’t already filled with nectar.

I found the marked and clipped queen on the very first super frame I removed.

Sod it.

Snatching victory from the jaws of defeat

Perhaps.

Here was the dilemma. Hive #29 was strong and healthy but effectively queenless. Time was against me. I didn’t have the luxury of simply plonking her beneath the QE and checking the colony didn’t make swarm preparations in another three or four weeks 11.¬†

I’d already united all my other colonies and made up the nucs. I didn’t want to disassemble any of these to accommodate this colony.

With bad weather approaching in a few days I decided to make up a nuc with the queen and, in due course, donate a queen cell from another colony.

Which is what I did. 

An adjacent colony helpfully raised several very good looking cells which I knew were charged. One of these, on a frame holding a sideplate-sized patch of brood, was added to the colony just before the rain arrived.

Open the box, open the box

But on the same day I added the queen cell I also checked the supers thoroughly.

I wanted to make sure that every frame was drone foundation and that I’d not missed a queen cell drawn from any worker comb in the supers. That might have resulted in a virgin queen running about in my supers and, knowing my luck, squeezing through the QE and slaughtering the queen from the cell I’d just introduced.¬†

There were lots of “queen cells” in the supers. However all were little more than play cups drawn along the top edge of the drone comb, against the top bar.¬†

Lots of drone brood … but no real queen cells

None contained eggs. It was as though the bees, sensing the colony was now truly queenless, had known what to do but had no primary material to work with.

Over the next fortnight or so this hive was going to generate hundreds thousands lots of drones. Not in itself a bad thing – this was a good colony and the positve influence on local bee genetics might be beneficial.

However, all the drones would emerge in the supers and be prevented from exiting the hive due to the queen excluder.

When this happens the drones die in their droves stuck half way through the excluder.

This is a distressing sight and, for a drone, a demoralising experience (I would imagine 12).

Under normal circumstances I would simply return every 3-4 days, pop the lid off the hive and release them. This wasn’t possible living four hours away …¬†

… so I played the ‘get out of jail free’ card by adding a thin eke and upper entrance.

Upper entrance

When I next check the colony I expect the drone brood to have all emerged and, largely, left the supers. I hope there’s a mated laying queen in the bottom box and there should be some capped worker brood.

What there’s unlikely to be is three full supers of honey ūüôĀ

With no worker brood being reared for at least 5 weeks the foraging workforce will be significantly depleted. I hope they manage to defend what they’ve already collected … time will tell.

What went wrong?

After finding the supers full of drone brood I wrote¬†“dodgy” on both sides of the queen excluder frame as I replaced it with a plastic spare.

I assumed the queen had found a bent wire and   s  q  u  e  e  z  e  d  her way through to have a field day Рactually three weeks Рin the supers.

However, I think the explanation is more prosaic than that 13.

My notes indicated I’d not seen the queen in this hive during the April inspection. In this instance evidence of absence was not absence of evidence … there were lots of eggs and brood in all staged. The colony was queenright and the queen was in the right place.

At least before I opened the hive ūüėČ

And this is where stupidity, forgetfulness and plain dumb luck played their part. I …¬†

  • stupidly botched the inspection, taking the strength and health of the colony as the most important signs that all was well, but …
  • forgot that the next inspection – when I would be making up nucs – would also need worker eggs in the brood box to rear new queens from.
  • There’s more … I also presumably forgot to thoroughly inspect the queen excluder before laying it to the side, allowing …
  • dumb luck to intervene when the queen scooted around to the other side of the excluder and so end up trapped in the supers when I reassembled the hive.

Mea culpa.

That’s my best guess anyway.

Did I do the right thing?

Hive #29 was the last to be inspected after a hard day of beekeeping in late April.

Coincidentally it was also the last to be checked in mid-May 14. 

This limited my options somewhat and I made a judgement call as to the best course of action. Doing what I describe above risks the queen failing to emerge or mate. It also potentially risks the box being robbed as the workforce diminish, particularly with the upper entrance I’ve added.

Both of these could lead to the loss of the hive, but the loss/problem would be all mine. At the time, standing there swearing sweating in my beesuit, gasping for a beer, it seemed like the safest bet. It also seemed like the responsible course of action in the middle of a global pandemic.

I chose not to just dump the queen back into the brood box, add the upper entrance and leave them to it. Had the colony subsequently swarmed 15 the problem might then have been someone else’s

Did I do the right thing?

We’ll know soon enough … ūüėČ


 

Who’s the daddy?

I’ve recently discussed the importance and influence of polyandry for honey bee colonies. Briefly, polyandry – the mating of the queen with multiple (~12-18) drones – is critical for colony fitness e.g. ability to resist disease, forage efficiently or overwinter successfully.

Hyperpolyandry, for example resulting from instrumental insemination of the queen with sperm from 30+ drones, further increases colony fitness and disease resistance.

How do you measure polyandry?

Essentially, you genetically analyse the worker bees in the colony to determine the range of patrilines present. Patrilines are genetically distinct offspring fathered by different drones. Essentially they are subfamilies within the colony.

With a finite number of patrilines – which there must be, because the queen does not mate with an infinite number of drones – there will be a point at which the more workers you screen the fewer new patrilines will be detected.

Search and ye shall find – detecting rare patrilines

The more you screen, the more you are likely to have detected all the patrilines present.

However, the queen uses sperm randomly when fertilising worker eggs. This compounds the difficulty in determining the full range of different patrilines present in a population. In particular, it makes detecting very rare patrilines difficult.

For example, if 20% of workers belong to one patriline you don’t need to sample many bees to detect it. In contrast, if another patriline is represented by 0.0001% of randomly selected workers you would probably have to screen thousands to be sure of detecting it.

Consequently, rare patrilines in the honey bee worker population are very difficult to detect. Inevitably this means that the number of drones the queen mates (~12-18) with is probably an underestimate of the actual number 1.

Half-sisters and super-sisters

Worker bees are often described as ‘half sisters’ to each other. They share the same mother (the queen), but different fathers.

Actually, as you should now realise, that’s an oversimplification because – with only ~12-18 different fathers contributing to the genetics of the colony – some workers are going to be more¬†related to each other because they share the same father and mother.

Half-sisters share the same mother but have different fathers and share about 25% of their genes.

Super-sisters share the same mother and father and so share about 75% of their genes (25% from the queen and 50% from the drone).

Super-sisters are more likely to help each other in the colony 2.

Emergency queens and nepotism

What’s the¬†most important decision a colony makes?

If the queen is killed (or removed) the workers rear new queens under the so-called ’emergency response’. They feed selected young larvae copious amounts of Royal Jelly to rear a replacement queen.

Arguably, the most important decision the workers make is the selection of the day-old larvae to rear as new queens.

If they get it wrong the colony is doomed. If they get it right the colony will flourish 3.

But as described above, workers are more or less related to each other genetically.

To ensure the continued propagation of at least some of their genes it might be expected that the nurse bees making this selection 4 would choose larvae more closely related to themselves.

Do worker bees exhibit nepotism when rearing emergency queens?

If workers were nepotistic you’d expect the¬†most common patrilines in the nurse/worker bee population would also predominate in the queens reared.

However, for at least 20 years evidence has been accumulating that indicates bees are not nepotistic. On the contrary, emergency queens appear to be reared from some of the rare patrilines in the colony.

A recent paper from James Withrow and David Tarpy has provided some of the best evidence for the existence of these so-called royal patrilines in honey bee colonies 5.

Royal patrilines

Evidence for these goes back to at least 1997 6, with about half a dozen publications in the intervening period. Essentially all used broadly the same approach; they genetically screened worker bees and the emergency queens they reared to determine which patrilines were present in the two groups. 

With certain caveats (size of study, number of microsatellites screened, colony numbers etc.) all concluded that colonies rear emergency queens from some of the rarest patrilines in the colony.

The recent study by Withrow and Tarpy is well explained and probably the most comprehensive, so I’ll use that to flesh out the details.

Experimental details

Six double-brood colonies were each split into a three separate colonies; a queenright single-brood colony and two five-frame nucs. The latter contained eggs and young larvae and so reared emergency queens.

Seven days later the developing emergency queens were all harvested for future analysis. One or two frames from the nucs were then exchanged with frames containing eggs and day-old larvae from the matched queenright colony.

The nucs then started rearing new queens … again.

And again … and again.

This process was repeated until the nucs failed.

In total over 500 queens were reared (to 7 days old) from these six original colonies. These queens were analysed genetically by microsatellite analysis, as were over 500 workers from colonies.

Within the 6 experimental colonies the authors identified a total of 327 patrilines (or subfamilies as Withrow and Tarpy describe them), ranging from 34-77 per colony. 108 patrilines (4-40 per colony) were exclusively detected in worker bees and 130 patrilines (5-55/colony) were exclusively detected in queens.

Cryptic “royal” subfamilies

Over 40% of queens raised per colony were produced from the patrilines exclusively detected in the queen population.

Subfamily distribution per colony.

As shown in the figure above, many queens (black bars) were reared from subfamilies (patrilines) not represented in the worker bee population (grey bars, sorted left to right by abundance).

Since there were different numbers of patrilines per colony (34-77), the bias towards the rarer patrilines is more apparent if you instead split them into tertiles (thirds) based upon worker abundance.

Are the queens predominantly reared from the most common tertile, the intermediate tertile or the rarest tertile?

Frequency distribution of subfamilies.

It’s very clear from this graph that workers select queens from the rarest patrilines within the colony.

It is therefore very clear that worker bees do not exhibit nepotism when choosing which larvae to rear emergency queen from.

Implications for our understanding of honey bee reproduction

Two points are immediately apparent:

  • there is a cryptic population of queen-biased patrilines that have largely been overlooked in genetic studies of honey bee polyandry
  • honey bee queens mate with more drones than conventional studies of worker bee patrilines indicate

Colony 5 had at least 77 distinct subfamilies (there might have been more detected had they screened more than the 94 workers and 135 queens from this colony). By extrapolation it is possible to determine that the effective queen mating frequency (me; the number of drones the queen had mated with) was ~32 if all the samples (worker and queen) were taken into account. If only the worker or queen samples were used for this calculation the effective queen mating frequency would be ~12 or ~65 respectively.

The average effective queen mating frequency over the six colonies was ~33 (total), significantly higher than the oft-quoted (including at the top of this page) me of ~12-18.

So perhaps honey bees really are hyperpolyandrous … or even extremely hyperpolyandrous as the authors suggest.

It’s worth noting in passing that routine mating frequencies over 30 are almost never quoted for honey bees 7, but that the ‘normal’ me ~12-18 is rather low when compared with other species within the genus Apis. The giant honey bee,¬†Apis dorsata, exhibits mating frequencies of greater than 60.

Who’s the daddy?

So, when it comes to emergency queens , although we might not know precisely who the daddy is, we can be pretty certain the particular patriline selected by the workers is most likely to be one of the rare ones in the colony.

Mechanistically, what accounts for this?

Are these larvae selected solely because they are rare?

That seems unlikely, not least because it would require some sort of surveying or screening by nurse bees. Not impossible perhaps, though I’m not sure how this would be achieved.

Perhaps it is not even worker selection?

An alternative way to view it is larval competition. A better competing larvae would be fed Royal Jelly and would be much more likely to pass on her genes to the next generation.

We don’t know the answers to these questions … yet.

Or whether they’re the wrong questions entirely.

Swarming and supercedure

The colony rears a new queen under three conditions; enforced queenlessness (as described above) which induces emergency queen rearing, prior to swarming and during supersedure.

These are fundamentally different processes in terms of the larvae used for queen rearing.

During swarming and supersedure 8 the queen lays the egg in a ‘play cup’ which is subsequently engineered into a queen cell in which the new queen develops.

Play cups

However, it is known that the patrilines of queens reared during the swarming response are similar to those of workers in the same colony 9, implying that there is no overt selection by the workers (or the parental queen).

Queen rearing

Does this insight into how bees rear new queens have any implications for how beekeepers rear new queens?

There are about as many queen rearing methods as there are adult workers in a double-brood colony in late June. Many  exploit the emergency queen rearing response by a colony rendered temporarily or permanently queenless.

Beekeepers often comment on the differential ‘take’ of grafted larvae presented to queenless cell raising colonies.

Sometimes you get very good acceptance of the grafted larvae, other times less so.

Of course, we only show the ones that worked well!

3 day old QCs ...

3 day old QCs …

Differential ‘take’ is often put down to the state of the cell raising colony or the nectar flow (or the cackhandedness of the grafter, or the phase of the moon, or about 100 other things).

I have never heard of beekeepers comparing the ‘take’ of larvae originating from the cell raising colony with those from another colony. The latter are always going to be ‘rare’ if you consider the patrilines present in the cell raising colony. However, grafts taken from the same colony as used for cell raising 10 are likely to reflect the predominant patrilines.

Are these accepted less well by the nurse bees?

I suspect not … but it is testable should anyone want to try.

My expectation would be that the presentation of larvae in a vertically oriented cell bar frame would likely override any genetic selectivity by the colony. They’re desperate to raise a new queen and – thank goodness – here’s a few that might do.

Alternatively, differential acceptance is more likely to reflect use of larvae of an unsuitable age, or that have been damaged during grafting.

As I listen to the wind howling outside it seems like a very long time until I can test any of these ideas … ūüôĀ


Colophon

Ray Winstone (as Carlin) 1979

Who’s the daddy? is British slang for who, or what, is the best. It originated in a line by Ray Winstone’s character Carlin from the 1979 film Scum. This was not a romantic comedy and I’m certainly not recommending viewing it. Nevertheless, the phrase became widely used over the subsequent couple of decades and seemed appropriate here because the colony is dependent on selecting high-quality larvae for colony survival.

Polyandry and colony fitness

Honey bees are polyandrous. The queen mates with multiple drones during her mating flight(s). Consequently, her daughters are of mixed paternity.

In naturally mated queens there is a relationship between the number of patrilines (genetically distinct offspring fathered by different drones) and the ‘fitness’ of a colony.

Colony fitness

A ‘fit’ colony is one that demonstrates one or more desirable traits (those that benefit the colony … and potentially the beekeeper) such as better population growth, weight gain, resistance to pathogens or survival.

If you analyse the molecular genotype of the worker offspring you can determine which patriline they belong to. If you genotype enough workers you start to see the same patrilines appearing again and again. The more patrilines, the more drones the queen mated with 1.

Shallow depth of field

One of many …

Naturally mated queens mate with ~13 drones. Depending upon the study a range from as low as 1 to as high as 40 (and exceptionally into the high 50’s) has been demonstrated, though different studies all tend to produce an average in the low- to mid-teens.

There is a well-established link between polyandry and colony fitness 2. Essentially, the more genetically diverse a colony i.e. the larger the number of patrilines, the fitter that colony is.

The benefits of polyandry

Why should colonies with increased genetic diversity be fitter?

There are a number of hypotheses that attempt to explain why intracolonial genetic diversity is beneficial. These include the increased behavioural repertoire of the worker bees, a reduced production of diploid drones (which would otherwise be produced due to the single-locus sex determination system) and an increased resistance to a wide range of parasites and pathogens 3.

Parasites and pathogens are an extremely effective evolutionary selective pressure. Several studies from David Tarpy and Thomas Seeley have shown that increased polyandry results in better resistance to chalkbrood and American foulbrood.

But what about¬†Varroa? It’s a new pathogen (evolutionarily speaking) to honey bees and there is evidence that the resistance mechanisms observed are genetically determined 4.

Does polyandry contribute to Varroa resistance? 

Would increased polyandry result in improved resistance to mites?

Limits of polyandry and natural resistance

Why is the average number of drone matings in the low teens?

If polyandry is beneficial – and there’s no doubt it is – then surely¬†more patrilines (hyperpolyandry) would be even more beneficial?

How could this be tested?

Naturally mated queens only very rarely exhibit 30+ drone matings. Not only are these colonies hard to find, but they are so rare that doing any sort of statistical analysis of the improved (or otherwise) fitness is probably a non-starter.

Perhaps there’s an alternative way to approach the question? Rather than look at individual colonies within a mixed population, why not study the overall level of polyandry within a population that demonstrates resistance?

For example, do queens that head colonies of untreated feral bees that exhibit a demonstrated enhanced resistance to Varroa, the most important pathogen of honey bees, exhibit higher levels of polyandry?

Two relatively recent scientific papers have tackled these questions. Both have produced clear answers.

Drones : if more is better, is lots more better still?

Yes.

Keith Delaplane and colleagues used instrumental insemination¬†(II) of virgin queens to produce queens ‘mated’ with 15, 30 or 60 drones. Sperm was collected from 1, 2 or 4 drones from 15 donor colonies, mixed thoroughly and used for queen insemination.

Full-sized colonies were requeened with the II queens and left for 6 weeks 5 after which sampling started. Over two seasons a total of 37 colonies (with 11, 13 and 13 colonies respectively headed by queens ‘mated’ with 15, 30 and 60 drones) were tested at approximately monthly intervals.

Testing involved visual analysis of colony strength 6 and comb construction. Mite levels were measured using standard alcohol wash of ~300 bees at mid- or late-summer timepoints.

Brood frame with a good laying pattern

The results of this study are commendably brief … just 8 lines of text and two tables. I’ll summarise them in just a couple of sentences.

Colonies headed by queens ‘mated’ with 30 or 60 drones produced significantly more brood than the colony headed by the queen ‘mated’ with only 15 drones. Conversely, significantly more colonies headed by queens mated with only 15 drones had a higher level of mite infestation 7.

Natural Varroa resistance and polyandry

One of the best studied populations of feral bees co-existing with Varroa are those in the Arnot Forest in New York State. These are the bees Thomas Seeley and colleagues study.

These colonies live in natural holes in trees at low density through the forest. The colonies are small and they swarm frequently. Their spatial distribution, size and swarminess (is that a word?) are all evolutionary traits that enable resistance, or at least tolerance, to Varroa and the pathogenic viruses the mite transmits.

I’ve discussed Seeley’s studies of the importance of colony size and swarming previously. I don’t think I’ve discussed his work on spatial separation of colonies, but I have described related studies by Delaplane and colleagues.

Essentially, by being well-separated, mite transmission between colonies (e.g. during robbing) is minimised. Similarly, by existing as small colonies that swarm frequently Iwith concomitant brood breaks) the mite population is maintained at a manageable level.

Marked queen surrounded by a retinue of workers.

Her majesty …

Do the Arnot Forest Varroa-resistant 8 bees exhibit especially high levels of polyandry, suggesting that this contributes their survival?

No.

Seeley and colleagues determined the number of patrilines in 10 Arnot Forest colonies using the same type of genotyping analysis described earlier. They compared these results to a similar analysis of 20 managed honey bee colonies located nearby.

On average, Arnot Forest queens had mated with ~18 drones (17.8 ¬Ī 9.8) each. In contrast, queens in managed colonies in two nearby apiaries had mated with ~16 and ~21 drones. These figures are not statistically different from each other or from the natural mating frequencies reported for honey bees in other studies.

Hyperpolyandry and colony fitness

The first of the studies confirms and extends earlier work demonstrating the polyandry (and in this instance hyperpolyandry i.e. at an even greater level than seen normally) increases colony fitness Рat least in terms of colony strength and Varroa resistance.

Delaplane and colleagues hypothesise that the increased mite resistance in hyperpolyandrous (30 or 60 drones) colonies may be explained by either:

  • the importance of extremely rare alleles (gene variants), which would only be present in colonies in which the queen had mated with a very large number of drones.
  • the presence of beneficial non-additive interactions between genetically-determined traits¬†e.g. grooming and hygienic behaviour and reduced mite reproduction.

Neither of which are mutually exclusive and both fit at least some of the extant data on natural mite resistance. Discriminating between these two hypotheses and teasing apart the variables will not be straightforward.

Absence of hyperpolyandry in naturally mite-resistant colonies

At first glance, the absence of the hyperpolyandry in the mite-resistant Arnot Forest bees studied by Thomas Seeley and colleagues appears to contradict the studies using the instrumentally inseminated queens.

The Arnot Forest bees exhibit the same level of polyandry as nearby managed colonies, and for that matter, as colonies studied elsewhere. They are mite-resistant but the queen has not mated with an increased number of drones.

In other studies 9, naturally mated colonies exhibiting different levels of polyandry (within the normal range) showed no correlation between Varroa levels and queen mating frequency.

Perhaps it’s surprising that the Arnot Forest queens hadn’t mated with fewer drones considering the extreme separation of the colonies (when compared with managed colonies). The colony density within the Forest is approximately one per square kilometre.

However, at least during the peak swarming and mating period in the season, drone availability is rarely limiting.

This is because drones are not evenly spread in the environment. Instead, they accumulate in drone congregation areas (DCA) to which the queen flies for mating.

What limits polyandry?

Polyandry is beneficial and, apparently, hyperpolyandry is more beneficial. However, queens mate with 10 – 20 drones, rather than 50 or more. Why is this?

Queen mating is a risky business. The queen has to fly to the DCA, mate with multiple drones and then return to the hive. She may make one or several mating flights.

I’ve discussed how far drones and queens fly to reach the DCA previously. Most drones fly less than 3 miles and 90% of matings occur within about 5 miles of the virgin queen’s hive. The queen probably flies further to the DCA.

All the time she is travelling to and from the DCA, and all the time she is present within it mating, she’s potentially at risk from hungry house martins, swallows, bee eaters (!) or from thunderstorms.

Or simply from getting lost.

Additionally, a number of honey bee pathogens are transmitted between drones and queens during mating. Hyperpolyandrous queens 10 are therefore at risk from these sexually transmitted diseases 11.

It’s therefore likely that the level of polyandry observed in honey bees has evolved as a consequence of the beneficial pressures polyandry brings balanced by the risks associated with mating multiple times.

Practical beekeeping

Although the two studies described here don’t have an immediate relevance to day-to-day practical beekeeping, it’s worth remembering that poor queen mating is regularly blamed for queen failures e.g.¬†queens that develop into drone layers during the winter.

I’m going to write about drones later this year so for the moment will just make these points:

  • drone production is maximised to generate sexually mature drones for the swarming season
  • after eclosion, drones need to mature before being able to mate
  • drones live about 30 days and their sperm volume, though not necessarily viability, decreases as they age

Together this means that late in the season – perhaps late July or early August (though this will vary depending upon location) – the number of drones will decrease.

More significantly, the drones will be ageing.

In turn this means that late-mated queens may not mate with as many drones, or that the matings may not result in insemination.

Most beekeepers will be aware of queens that apparently ‘run out of sperm’ and become drone layers.

However, there may be less obvious problems with late-mated queens. I’m not aware of any studies on seasonality of queen mating and polyandry. However,¬†I would not be at all surprised if they exhibited a reduced level of polyandry.

And, as described above, these colonies are likely to exhibit reduced fitness.

Something else to consider when deciding whether to unite a colony late in the season or hope the last of your virgin queens mates successfully …


 

Women without men

The title of the post last week was The end is nigh which, looking at the fate of drones this week, was prophetic.

Shallow depth of field

Watch your back mate … !

After the ‘June gap’ ended queens started laying again with gusto. However, there are differences in the pattern of egg laying when compared to the late spring and early summer.

Inspections in mid/late August 1 show clear signs of colonies making preparations for the winter ahead.

For at least a month the amount of drone brood in colonies has been reducing (though the proportions do not change dramatically). As drones emerge the cells are being back-filled with nectar.

Seasonal production of sealed brood in Aberdeen, Scotland.

The data in the graph above was collected over 50 years ago 2. It remains equally valid today with the usual caveats about year-to-year variation, the influence of latitude and local climate.

Drones are valuable …

Drones are vital to the health of the colony.

Honey bees are polyandrous, meaning the queen mates with multiple males so increasing the genetic diversity of the resulting workers.

There are well documented associations between colony fitness and polyandry, including improvements in population growth, weight gain (foraging efficiency) and disease resistance.

The average number of drones mating with a queen is probably somewhere between 12 and 15 under real world conditions. However studies have shown that hyperpolyandry further enhances the benefits of polyandry. Instrumentally inseminated queens “mated” with 30 or 60 drones show greater numbers of brood per bee and reduced levels of¬†Varroa infestation.

Why don’t queens¬†always mate with 30-60 drones then?

Presumably this is a balance between access, predation and availability of drones. For example, more mating would likely necessitate a longer visit to a drone congregation area so increasing the chance of predation.

In addition, increasing the numbers of matings might necessitate increasing the number of drones available for mating 3.

… and expensive

But there’s a cost to increasing the numbers of drones.

Colonies already invest a huge amount in drone rearing. If you consider that this investment is for colony reproduction it is possible to make comparisons with the investment made in workers for reproduction i.e. the swarm that represents the reproductive unit of the colony.

Comparison of the numbers of workers or drones alone is insufficient. As the graph above shows, workers clearly outnumber drones. Remember that drones are significantly bigger than workers. In addition, some workers are not part of the ‘reproductive unit’ (the swarm).

A better comparison is between the dry weight of workers in a swarm and the drones produced by a colony during the season.

It’s worth noting that these comparisons must be made on colonies that make as many drones as they want. Many beekeepers artificially reduce the drone population by only providing worker foundation or culling drone brood (which I will return to later).

In natural colonies the dry weight of workers and drones involved in colony reproduction is just about 1:1 4.

Smaller numbers of drones are produced, but they are individually larger, live a bit longer and need to be fed through this entire period. That is a big investment.

Your days are numbered

And it’s an investment that is no longer needed once the swarming season is over. All those extra mouths that need feeding are a drain on the colony.

Even though the majority of beekeepers see the occasional drone in an overwintering colony, the vast majority of drones are ejected from the hive in late summer or early autumn.

About now in Fife.

In the video above you can see two drones being harassed and evicted. One flies off, the second drops to the ground.

As do many others.

There’s a small, sad pile of dead and dying drones outside the hive entrance at this time of the season. All perfectly normal and not something to worry about 5.

Drones are big, strong bees. These evictions are only possible because the workers have stopped feeding them and they are starved and consequently weakened.

A drone’s life … going out with a bang … or a whimper.

An expense that should be afforded

Some of the original data on colony sex ratios (and absolute numbers) comes from work conducted by Delia Allen in the early 1960’s.

Other colonies in these studies were treated to minimise the numbers of drones reared. Perhaps unexpectedly these colonies did not use the resources (pollen, nectar, bee bread, nurse bee time etc) to rear more worker bees.

In fact, drone-free or low-drone colonies produced more bees overall, a greater weight of bees overall and collected a bit more honey. This strongly suggests that colonies prevented from rearing drones are not able to operate at their maximum potential.

This has interesting implications for our understanding of how resources are divided between drone and worker brood production. It’s obviously not a single ‘pot’ divided according to the numbers of mouths to feed. Rather it suggests that there are independent ‘pots’ dedicated to drone or worker production.

Late season mating and preparations for winter

The summer honey is off and safely in buckets. Colonies are light and a bit lethargic. With little forage about (a bit of balsam and some fireweed perhaps) colonies now need some TLC to prepare them for the winter.

If there’s any reason to delay feeding it’s important that colonies are not allowed to starve. We had a week of bad weather in mid-August. One or two colonies became dangerously light and were given a kilogram of fondant to tide them over until the supers were off all colonies and feeding and treating could begin. I’ll deal with these important activities next week.

In the meantime there are still sufficient drones about to mate with late season queens. The artificial swarm from strong colony in the bee shed was left with a charged, sealed queen cell.

Going by the amount of pollen going in and the fanning workers at the entrance – see the slo-mo movie above – the queen is now mated and the colony will build up sufficiently to overwinter successfully.


Colophon

Men without Women

Men without women was the title of Ernest Hemingway’s second published collection of short stories. They are written in the characteristically pared back, slightly macho and bleak style that Hemingway was famous for.

Many of these stories have a rather unsatisfactory ending.

Not unlike the fate of many of the drones in our colonies.

Women without men is obviously a reworking of the Hemingway title which seemed appropriate considering the gender-balance of colonies going into the winter.

If I’d been restricted to writing using the title¬†Men without Women I’d probably have discussed the wasps that plague our picnics and hives at this time of the year. These are largely males, indulging in an orgy of late-season carbohydrate bingeing.

It doesn’t do them any good … they perish and the hibernating overwintering mated queens single-handedly start a new colony the following spring.

Sphere of influence

How far do honey bees fly? An easy enough question, but one that is not straightforward to answer.

The flight range of the honeybee ...

The flight range of the honeybee …

Does the question mean any honey bee i.e. workers, drones or the queen? As individuals, or as a swarm?

Is the question how far can they fly? Or how far do they usually fly?

Why does any of this matter anyway?

Ladies first …

Workers

The first definitive experiments were done by John Eckert in the 1930’s. He located apiaries in the Wyoming badlands at increasing distances from natural or artificial forage 1. Essentially the bees were forced to fly over a moonscape of rocks, sand, sagebrush and cacti to reach an irrigated area with good forage. He then recorded weight gain or loss of the hives located at various distances from the forage.

Wyoming badlands

Wyoming badlands …

The original paper can be found online here (PDF). The experiments are thorough, explained well and make entertaining reading. They involved multiple colonies and were conducted in three successive years.

Surprisingly, Eckert showed that bees would forage up to 8.5 miles from the colony. This means they’d be making a round trip of at least 17 miles – and probably significantly more – to collect pollen and nectar.

However, although colonies situated within 2 miles of the nectar source gained weight, those situated more than 5 miles away lost weight during the experiments.

Gain or loss in hive weight ...

Gain or loss in hive weight …

Therefore, bees can forage over surprisingly long distances, but in doing so they use more resources than they gain.

John Eckert was the co-author (with Harry Laidlaw) of one of the classic books on queen rearing 2. His studies were probably the first thorough analysis of the abilities of worker bees to forage over long distances. Much more recently, Beekman and Ratnieks interpreted the waggle dance (PDF) of bees to calculate foraging distances to heather. In these studies, only 10% of the bees foraged ~6 miles from the hive, although over 50% travelled over 3.5 miles.

Queens

Queens don’t get to do a lot of flying. They go on one or two matings flights, perhaps preceded by shorter orientation flights, and they might swarm.

Heading for a DCA near you ...

Heading for a DCA near you …

I’ll deal with swarms separately. I’ll also assume that the orientation flights are no greater than those of workers (I don’t think there’s any data on queen orientation flight distance or duration) at no more than ~300 metres 3.

On mating flights the queen flies to a drone congregation area (DCA), mates with multiple drones and returns to the colony. DCA’s justify a complete post of their own, but are geographically-defined features, often used year after year.

There are a number of studies on queen mating range using genetically-distinguishable virgin queens and drones in isolated or semi-isolated locations. They¬†‚Äėdo what they say on the tin‚Äô, drone congregate there and wait for a virgin queen

In the 1930’s Klatt conducted studies using colonies on an isolated peninsula and observed successful mating at distances up to 6.3 miles

Studies in the 1950’s by Peer demonstrated that matings could occur between queens and drones originally separated by 10.1 miles 4. These studies showed an inverse relationship between distance and successful mating.

More recently, Jensen et al., produced data that was in agreement with this, with drone and queen colonies separated by 9.3 miles still successfully mating 5.

However, this more recent study also demonstrated that more than 50% of matings occurred within 1.5 miles and 90% occurring within 4.6 miles.

Just because they can, doesn’t mean they do ūüôā

Drones … it takes 17 to tango …

Seventeen of course, because that’s one queen and an average of 16 drones ūüėČ

There’s a problem with the queen mating flight distances listed above. Did the queen fly 9 miles and the drone fly just a short distance to the DCA?

Or vice versa?

10 miles ... you must be joking!

10 miles … you must be joking!

Or do they meet in the middle?

Do queens choose 6 to fly shorter distances because it minimises the risk of predation and because they are less muscle-bound and presumably less strong flyers than drones?

Alternatively, perhaps drones have evolved to visit local DCAs to maximise the time they have aloft without exhausting themselves flying miles first?

Or getting eaten.

It turns out that – at least in these long-distance liaisons – it’s the queen that probably flies further. Drones do prefer local DCAs 7 and most DCAs are located less than 3 miles from the ‘drone’ apiary 8.

Swarms

I’ve discussed the relocation of swarms recently. Perhaps surprisingly (at least in terms of forage competition), swarms prefer to relocate relatively near the originating hive. Metres rather than miles.

The sphere of influence

Effective foraging – in terms of honey production (or, for that matter, brood rearing) – occurs within 2-3 miles of the hive. This distance is also the furthest that drones usually fly to occupy DCAs for mating.

Queens can fly further, but it’s the law of diminishing returns.¬†Literally.¬†The vast majority of matings occur within 5 miles of the hive.

In fact, other than under exceptional circumstances, a radius of 5 miles from a colony probably represents its ‘sphere of influence’ … either things that can influence the colony, or that the colony can influence.

Why does this matter?

Worker flight distances are relevant if you want to know the nectar sources your bees are able to exploit, or the pollination services they can provide. In both cases, closer is better. It used to also be relevant in trying to track down the source of pesticide kills, though fortunately these are very much rarer these days.

Closer is better ...

Closer is better …

Workers not only fly to forage on plants and trees. They also fly to rob other colonies. I don’t think there are any studies on the distances over which robbing can occur, but I’ve followed bees the best part of a mile across fields from my apiary to find the source of the robbing 9.

All of these movements can also transport diseases about, either in the form of phoretic Varroa mites piggybacking and carrying a toxic viral payload, or as spores from the foulbroods.

Drone and queen flight distances are important if you’re interested in establishing isolated mating sites to maintain particular strains of bees. My friends in the Scottish Native Honey Bee Society have recently described their efforts to establish an isolated queen mating site in the Ochil Hills.

And I’m interested as I now have access to a site over 6 miles from the nearest honey bees in an area largely free of Varroa.

It’s not the Wyoming badlands, but it’s very remote ūüôā


 

Apis mellifera aquaticus

Early June 2017 ...

Early June 2017 …

June in Fife was the wettest year on record. It started in a blaze of glory but very quickly turned exceedingly damp. The photo above was taken on the 7th of June. One of my apiaries is in the trees at the back of the picture. Six queens emerged on the 2nd¬†or 3rd of June to be faced with a week-long deluge. The picture was taken on the first dry morning … by the afternoon it was raining again, so delaying their ability to get out and mate (hence prompting the recent post).

And so it continued …

Early July 2017 ...

Early July 2017 …

Here’s the same view on the 1st of July. Almost unchanged … ankle deep water¬†en route to the apiary, the burn in flood and some splits and nucs now being fed fondant to prevent them starving.

A beautiful morning though ūüėČ

Retrospective weather reports

Of course, you shouldn’t really worry about weather that’s been and gone, though comparisons year on year can be interesting. At the very least, knowing that the June monthly rainfall in Eastern Scotland was 223% of the 1961-99 average, I’ll have an excuse why queens took so long to mate and why the June gap was more pronounced than usual. Global warming means summers are getting wetter anyway, but even if you make the comparison with the more recent 1981-2010 average we still got 206% of the June monthly total.

The Met Office publishes retrospective summaries nationally and by region. These include time series graphs of rainfall and temperature since 1910 showing how the climate is getting warmer and wetter. If you prefer, you can also view the data projected on a map, showing the marked discrepancies between the regions.

June 2017 rainfall anomaly from 1981-2010

June 2017 rainfall anomaly cf. 1981-2010 …

Parts of the Midlands and Lewis and Harris were drier than the June long-term average, but Northern England and Central, Southern and Eastern Scotland were very much wetter.

It would be interesting to compare the year-by-year climate changes with the annual cycle of forage plants used by bees. Natural forage, rather than OSR where there is strain variation of flowering time, would be the things to record. As I write this (first week of July) the lime is flowering well and the bees are hammering it. The rosebay willow herb has just started.

Rosebay willow herb

Rosebay willow herb

Prospective weather forecasts

Bees are influenced by the weather and so is beekeeping. If the forecast is for lousy weather for a fortnight it might be a good idea to postpone queen rearing and to check colonies have sufficient stores. If rain is forecast all day Saturday then inspections might have to be postponed until Sunday.

If you have a bee shed you¬†can inspect when it’s raining. The bees tolerate the hive being opened much better than if it were out in the open. Obviously, all the bees will be in residence, but their temper is usually better. They exit the shed through the window vents and rapidly re-enter the hive through the entrance.

I don’t think there’s much to choose between the various online weather forecast sites in terms of accuracy, particularly for predictions over 3+ days. They’re all as good or as bad as each other. I cautiously use the BBC site, largely because they have an easy-to-read app for my phone.

Do I need an umbrella?

For shorter-term predictions (hours rather than days) I’ve been using Dark Sky. This can usefully – and reasonably accurately – predict that it will start raining in 30 minutes and continue for an hour, after which it will be dry until 6pm.

The forecast in your area might be different ūüėČ

Dark Sky via web browser

Dark Sky via web browser

There’s a well designed app for iOS and Android as well that has neat graphics showing just how wet you’re likely to get, how long the rain will last and which direction the clouds will come from.

Dark Sky on iOS

Dark Sky on iOS

It’s far from perfect, but it’s reasonably good. It might make the difference between getting to the apiary as the rain starts as opposed to having a nice cuppa and then setting off in an hour or two.

Rain stopped play

I’ve posted recently on delays to queen mating caused by the poor weather in June. I’ve now completed inspections of all the splits. Despite both keeping calm and having patience I was disappointed to discover that the last two checked had developed laying workers. Clearly the queen was either lost on her mating flight or – more likely (see the pictures above) – drowned.

I’ve previously posted how I deal with laying workers – I shake the colony out and allow those that can fly to return to a new hive on the original site containing a single frame of eggs and open brood. If they start to draw queen cells in 2-3 days I reckon the colony is saveable and either let them get on with it, or otherwise somehow make them queenright.

One of the laying worker colonies behaved in a textbook manner. A couple of days after shaking them out there were queen cells present. I knocked these back and united the with a spare nuc colony containing a laying queen.

Lime can yield well in July

Lime can yield well in July

The second colony behaved very strangely. I didn’t manage to inspect them until a week after shaking them out. There were no queen cells. Nor was there any evidence of laying worker activity in the frames of drawn comb I’d provided them with. Instead, they’d filled the brood box with nectar from the nearby lime trees. Weird. I united them with a queenright colony and I’ll check how they progress over the next week or two.

Apis mellifera aquaticus

My colonies are usually headed by dark local mongrel queens. My queen rearing records show that some are descended from native black bees (Apis mellifera mellifera) from islands off the West coast of Scotland, albeit several generations ago. These bees are renowned for their hardiness, ability to forage in poor weather and general suitability to the climate of Scotland.

Nevertheless, without further natural selection and evolution they will have still needed water wings, a snorkel and flippers to get mated last month ūüėČ

Not waving but drowning


Colophon

Carl Linnaeus

Carl Linnaeus

The taxonomic scheme ‘developed’ by Carl¬†Linnaeus (1707 – 1778) is a rank-based classification approach actually dates back to Plato. In it, organisms are divided into kingdoms (Animals), classes (Insecta), order (Hymenoptera), family (Hymenoptera), genera (Apis) and species (mellifera).

The subspecies is indicated by a further name appended to the end of the species name e.g. Apis mellifera capensis (Cape Honey bees), Apis mellifera mellifera (Black bees)

Apis mellifera aquaticus doesn’t really exist, but might evolve if it remains this wet ūüėČ

Worker laying workers

A few months ago I wrote about problems encountered with laying workers, and ways to overcome those problems. Laying workers occur when a colony lacks sufficient open brood pheromone to suppress egg laying by the workers. One solution, though not one I favour, is to repeatedly add frames of open brood to suppress egg laying and then either add a queen, or allow the colony to raise their own.

The article was titled ‘drone laying workers’ and, in the comments, Tim Foden correctly pointed out that the prefix ‘drone’ was probably superfluous. Since the workers were unmated they would only be able to lay haploid eggs which would inevitably develop into drones.

Without intervention a laying worker colony is doomed. However, drones from a laying worker colony are fertile. Therefore, from an evolutionary perspective you could consider the rearing of drones is a last-gasp effort to pass on some of the genes to successive generations.

But … there’s always a but

The Cape honey bee (Apis mellifera capensis) is¬†a subspecies usually restricted to the Western Cape region of South Africa. Laying workers of Cape honey bees can lay eggs that develop into workers (or queens). Since these ‘mother’ workers are unmated and their resulting progeny workers are diploid, this takes some genetic trickery. This mechanism is snappily titled¬†thelytokous parthenogenesis.

Cape honey bees

Cape honey bees

Parthenogenesis is most simply defined as reproduction without fertilisation. Thelytoky is derived from the Greek¬†thelos, meaning ‘female’, and¬†tokos, meaning ‘birth’. The next time you’re asked to define thelytokous parthenogenesis in the pub quiz your team will have the edge –¬†it means giving birth to females without reproduction. The female progeny¬†capensis workers produce can be reared as workers – essentially clones of their mothers – or, with a change in diet for the early larvae, queens.

The genetic trickery involves the haploid pronucleus of the egg fusing with one of the polar bodies that are generated during oogenesis (egg production). Polar bodies are small haploid cells that bud off during ovum development. Fusion of the two haploid cells creates a diploid, which can go on to become a female bee.

No laying worker problems then … ?

Quite the opposite.¬†You’d think that by encouraging this type of activity in Cape honey bees your laying worker problems would be a thing of the past. In fact, your problems become a thing of the future. Laying workers of¬†capensis are socially parasitic. They invade – through drifting¬†for example – unrelated neighbouring colonies, such as those of¬†Apis mellifera¬†scutellata¬†(another subspecies, the African honey bee). Once there, the eggs they lay are reared by the new colony, but the resulting workers do not contribute to foraging or other hive activities. Instead they also become laying workers (worker laying workers that is ūüėČ ), eventually leading to the collapse of the host colony.

Capensis has been spread widely from its original range through migratory beekeeping, leading to large-scale colony losses and significant economic impact to the beekeeping industry in regions of South Africa distant from the Western Cape. Capensis also hybridises with scutellata in areas where their ranges overlap.

Divide and conquer

Honey bees are social insects. Cape honey bees, for all their unsociable parasitic activities are also social. However, their unsociable activities aren’t restricted to parasitism. They also exhibit a trait called¬†worker policing. A Cape honey bee colony might contain several laying workers. The workers they rear are able to discriminate between eggs laid by their ‘mother’ and those laid by her half-sisters – effectively their aunts – in the same hive. Once they detect a foreign egg, they either eject it or eat it.

This worker policing can lead to sub-division of the hive, with territories being established in separate parts of the hive, each containing genetically clonal populations of laying workers. However, unless the colony rears a new queen its long-term prospects are very limited. The prodigious egg-laying ability of a queen far outstrips that of even multiple laying workers, meaning the colony – and all its sub-divisions – will eventually dwindle and be lost.

Worker policing is an interesting phenomenon and has some relevance to queen rearing and larval selection which I’ll address later in the season.

Pedantically speaking … and wind

Laying workers colonies in the UK characteristically rear large numbers of drones. This is why Tim Foden correctly commented¬†that the prefix ‘drone’ is superfluous. However, to be absolutely pedantic it is needed. This is because,¬†irrespective of the strain of bee, up to¬†1% of eggs laid by laying workers are diploid. All bees exhibit¬†thelytokous parthenogenesis¬†but it’s only¬†in¬†capensis the trait is common.

Why is it only in¬†capensis that this trait is common? It’s been suggested the selection for¬†thelytokous parthenogenesis is due to the strong winds that occur in the southern region of South Africa in which¬†capensis is the native honey bee. As a consequence of this, queens are often lost on mating flights, rendering the colony queenless. Without “worker laying workers” ¬†– or, more correctly, diploid laying workers from which new queens can be raised –¬†colonies would be doomed.

Western Cape Fynbos region of South Africa

Western Cape Fynbos region of South Africa

Capensis queen mating flights have been documented at¬†wind speeds in excess of 30 mph … another adaptation to the climate of the region. In contrast,¬†scutellata¬†queens,¬†from more northerly regions in South Africa won’t go on mating flights if the wind speed exceeds¬†~12 mph.

Cape honey bees are wonderfully well adapted to the Western Cape Fynbos region of South Africa. They are the strain beekeepers choose to use for honey production and pollination in an area with huge biodiversity and ~6000 endemic plant species. In trials using alfalfa,¬†capensis-pollinated plants set twice as much seed¬†as those pollinated by¬†scutellata. This suggests they are particularly thorough plant ‘visitors’, a conclusion supported by their ability to collect pollen which was also twice that of¬†scutellata. They have additional unique characteristics. In a publication pre-dating the introduction of¬†Varroa to South Africa, Hepburn and Guillarmod¬†(PDF) describe how readily¬†capensis absconds in summer and migrates in winter, both characteristics the reflect adaptation to the climate and the regular wildfires in the region, and not seen in other strains of bees.

Finally, in much the same way that moving capensis colonies elsewhere has caused problems, the introduction of American foulbrood to the region in 2008 (again through beekeeper activity) has resulted in the loss of 40% of Cape honey bees.

 

Last of the drones

At the inspections last weekend there was only one colony with obvious numbers¬†of drones present. We’ve had nearly a full month with no appreciable nectar flow and the colonies have almost all ejected the drones. Here’s¬†one of the few that were left:

Last of the drones

Last of the drones

 

Not long mate until you too are chucked out during the autumn purge. Watch your back!

This colony was a swarm that was attracted to a bait hive in early June. I don’t know whether bee genetics influences the time when drones are ejected from the hive, but it’s notable that almost all the other queens in the apiary are half sisters (unrelated to the queen from the swarm) and there wasn’t a drone to be seen in half a dozen hives. The other notable thing about this colony is that the¬†Varroa levels remain stubbornly high despite three treatments by sublimation. I’m just starting a second series of treatments to get the numbers¬†down to a more acceptable level.

Take one for the team

You know it makes sense

You know it makes sense

…¬†would have been a much better title for an¬†interesting recent paper on the impact of¬†Varroa¬†on honey bee colonies. More specifically, the snappily titled¬†“Social apoptosis in honey bee¬†super organisms”¬†(Page et al., 2016¬†Scientific Reports¬†6: 27210¬†doi:10.1038/srep27210)¬†attempts to answer how and why the natural host of¬†Varroa, the Eastern honey bee (Apis cerana), copes with mite infestation whereas ‘our’ bees (Apis mellifera), the Western honey bee, succumbs within 2-3 years without mite-control?¬†The paper is Open Access so you don’t need to pay to read it and you can find it here.

Only the good damaged die young †

The authors demonstrate that A. cerana mite-associated pupae die before they emerge, whereas those of A. mellifera do not. As a consequence of this the mite levels are unable to build up to damaging levels in the colony. Essentially the pupae on which the mites feed die very quickly, meaning the mite also dies. They determined this by uncapping and examining age-matched pupae one day before natural emergence (see below) in Varroa-infested or uninfested colonies. Varroa-associated pupae (upper row in the image below) had all died during pupation.

Infested (above) and control (below) A. cerana pupae

Infested (above) and control (below) A. cerana pupae

In an extension to this study the authors showed that puncturing pupae with a sterile glass needle and then re-sealing the cell (you can do this with gelatin) also results in the pupae dying. The needle used had the same diameter as the chelicerae of the Varroa mite, so this treatment recapitulated the physical damage caused by the mite.¬†Since the needle was sterile it was¬†unlikely that the pupae were¬†dying from exposure to the viruses (or other pathogens) transmitted by the¬†Varroa mite. Instead, it seems that the Eastern honey bee has evolved mechanisms of “self-sacrifice” in response to wounding that result in the death of damaged pupae before the infesting mite has had a chance to multiply. Clever.

Social apoptosis

Apoptosis is the term used by cell biologists to describe a series of events that are also called programmed cell death seen, for example, in virus-infected cells. If a cell detects that it is virus infected, a cascade of signalling events result in it undergoing apoptosis (it dies), so preventing the infecting virus from replicating properly and spreading to neighbouring cells in the organism. Social apoptosis is a similar process, the death of an infected Рor infested Рmember of the superorganism, the honey bee colony.

Immunity is a term meaning ‘having resistance to’, for example¬†immunity to measles due to prior vaccination or infection. Generally, immunity is a reflection of strength of the recipient or exposed to the ‘abuse’ caused by the infectious agent. In contrast, the mechanism described for A. cerana¬†is the opposite of this, instead being a¬†form of immunity through weakness or susceptibility.

A. cerana has additional resistance mechanisms that help it combat¬†Varroa infestation including enhanced grooming, removal of mites from unsealed brood, entombing multiply mite-associated drone brood (it’s not clear to me whether this is the same mechanism as the social apoptosis reported here), increased hygienic behaviour and¬†shorter developmental cycles. These will have evolved over the millennia that the mite and bee have associated.

Any chance A. mellifera will evolve a similar mechanism?

Possibly, but I’m not holding my breath. There are already hygienic strains of¬†A. mellifera –¬†for example, VSH bees developed by the USDA group at Baton Rouge. These typically uncap and discard¬†Varroa-associated pupae. This isn’t the same process as the social apoptosis reported here¬†in¬†A. cerana. The latter¬†pupae die prematurely, thereby preventing mite reproduction. While we’re on the subject of Varroa and genetic resistance – do VSH¬†A. mellifera strains¬†open and discard mite-associated pupae … a)¬†early enough to prevent significant levels of mite replication, and b) without releasing progeny mites from the cells they were raised in? I’m aware of the rates at which they clear out¬†Varroa infested cells, but not either the timing of these events or the fate of any¬†Varroa released at the same time.

It’s difficult to imagine a practical strategy to select for A. mellifera honey bee¬†pupae that are¬†more sensitive to¬†Varroa infestation … our bees are currently too robust.


‚Ć Billy Joel wrote¬†Only the good die young which appeared on his 1977 album¬†The Stranger. “[Not] so much anti-Catholic as pro-lust” Joel explained when it was censored, inevitably¬†ensuring its chart success. The song¬†has more to do with the birds and the bees …¬† ūüėČ

 

The bee house

After the bee shed comes the bee house. However, in a break from tradition, this is a post about solitary bees rather than honey bees. Solitary bees include things like the Red Mason Bee. These were very common where I lived in the Midlands but this species of solitary bee is very much rarer in Scotland, although they are present in parts of Fife.

Red mason bee

Red mason bee …

Steven Falk book

Steven Falk book

I’ve no idea what’s about in this area of Fife so I’m putting up a couple of solitary bee houses to see if I can attract any … and then I’ll try and¬†identify them. To help with the latter I’ve recently been given¬†a copy of the excellent Field Guide to the Bees of Great Britain and¬†Ireland by Steven Falk. For beekeepers this book is a bit of a reality check … in ~430 pages densely packed with wonderful photographs, drawings and descriptions of bees of all shapes and sizes,¬†Apis mellifera – the honey bee – gets just 2 pages. Pro rata, that’s perhaps a bit¬†too much considering¬†‘our’ bee¬†is just one of the 285 species in the UK and Ireland.¬†To get an idea of the quality of the illustrations I suggest having a look at some of the outstanding photographs on¬†Steven’s Flickr account … and don’t just restrict yourself to his bee photo collection.

Blue Mason Bee?

Blue Mason Bee?

There are lots of descriptions online about how to make houses for solitary bees. You can also buy them (often at¬†silly prices) from garden centres and gift shops. However, they’re easy and much cheaper to make, and can be made to suit a much wider range of solitary bees with a little bit of effort, a few bits of untreated wood and a drill. Mine are even simpler than that … I just use a short length of plastic drainpipe stuffed with hollow bamboo canes.¬†I make sure the drainpipe is a bit longer than the canes – to provide a sheltered entrance – and just stuff them in so tightly that the drainpipe distorts slightly. These aren’t particularly aesthetically pleasing, but they’ve worked well before.¬†I’ve additionally got a few¬†Grow Wild bee houses that come flat-packed in the Grow Wild flower seed kits. If you’re not familiar with these then make sure you¬†register in 2017 and get some mixed wildflower seeds appropriate to your region. I’ve not used these bee houses before, they have a plastic outer with a hanging loop together with 10 cardboard tubes. These are perhaps a little too regular in diameter – you want some variation as not all solitary bees use the same sized holes. However, I’m sure it will still work. In comparison to some of the fancy commercial offerings these little plastic triangular prisms are more like bee tents than bee hotels.

Bee house on the bee shed ...

Bee house on the bee shed …

The solitary bee house needs to be securely mounted off the ground, between about waist and head height, in a warm and sunny – but reasonably sheltered – position. Above the patio of our last house I zip-tied them to the drainpipes well above head height so they didn’t bother us when we were outside. Here I’ve put them on the back of the¬†house and – perhaps appropriately – under the eaves of the bee shed.

Now all we need is the the weather to warm up and see what arrives …


And finally … you’ll note I make a distinction between my bee shed and both the¬†solitary bee houses I discuss here and the extraordinary edifice below (a honey bee house). It all looks a bit precarious, both in terms of the construction and from a beekeeping point of view. The top row of hives must have to be inspected from the top of a ladder. It looks like the building is set into the slope behind and so there’s not a similar number of hives on the other two sides.

Now that's what I call a real bee house ...

Now that’s what I call a real bee house …

I can see a dirty great crack in the wall at the bottom of the image. Nevertheless, I bet sitting in that garden chair in the middle of the picture is a great experience when there’s a good nectar flow on and the air is thick with returning foragers.