Category Archives: Diseases

Aristotle’s hairless black thieves

Aristotle not in his beesuit

Almost every article or review on chronic bee paralysis virus 1 starts with a reference to Aristotle describing the small, black, hairless ‘thieves‘, which he observed in the hives of beekeepers on Lesbos over 2300 years ago 2.

Although Aristotle was a great observer of nature, he didn’t get everything right.

And when it came to bees, he got quite a bit wrong.

He appreciated the concept of a ‘ruling’ bee in the hive, but thought that the queen was actually a king 3. He also recognised different castes, though he thought that drones (which he said “is the largest of them all, has no sting and is stupid”) were a different species.

He also reported that bees stored noises in earthenware jars (!) and carried stones on windy days to avoid getting blown away 4.

However, over subsequent millenia, a disease involving black, hairless honey bees has been recognised by beekeepers around the world, so in this instance Aristotle was probably correct.

Little blacks, maladie noire, schwarzsucht

The names given to the symptomatic bees or the disease include little blacks or black robbers in the UK, mal nero in Italy, maladie noire in France or schwarzsucht (black addiction) in Germany. Sensibly, the Americans termed the disease hairless black syndrome. All describe the characteristic appearance of individual diseased bees.

Evidence that the disease had a viral aetiology came from Burnside in the 1940’s who demonstrated the symptoms could be recapitulated in caged bees by injection, feeding or spraying them with bacterial-free extracts of paralysed bees. Twenty years later, Leslie Bailey isolated and characterised the first two viruses from honey bees. One of these, chronic bee paralysis virus (CBPV), caused the characteristic symptoms described first by Aristotle 5.

CBPV causes chronic bee paralysis (CBP), the disease first described by Aristotle.

CBPV infection is reported to present with two different types of symptoms, or syndromes. The first is the hairless, black, often shiny or greasy-looking bees described above 6. The second is more typically abnormal shivering or trembling of the wings, often associated with abdominal bloating 7. These bees are often found on the top bars of the frames during an inspection. Both symptoms can occur in the same hive 8.

CBP onset appears rapid and the first thing many beekeepers know about it is a large pile (literally handfuls) of dead bees beneath the hive entrance.

It’s a distressing sight.

Despite thousands of bees often succumbing to disease, the colony often survives though it may not build up enough again to overwinter successfully.

BeeBase has photographs and videos of the typical symptoms of CBPV infection.

Until recently, CBP was a disease most beekeepers rarely actually encountered.

Emerging and re-emerging disease

I’ve got a few hundred hive year’s worth 9 of beekeeping experience but have only twice seen CBP in a normally-managed colony. One was mine, another was in my association apiary a few years later.

A beekeeper managing 2 to 3 colonies might well never see the disease.

A bee farmer running 2 to 3 hundred (or thousand) colonies is much more likely to have seen the disease.

As will become clear, it is increasingly likely for bee farmers to see CBP in their colonies.

Virologists define viral diseases as emerging if they are new in a population. Covid-19, or more correctly SARS-CoV-2 (the virus), is an emerging virus. They use the term re-emerging if they are known but increasing in incidence.

Ebola is a re-emerging disease. It was first discovered in humans in 1976 and caused a few dozen sporadic outbreaks 10 until the 2013-16 epidemic in West Africa which killed over 11,000 people.

Often the terms are used interchangeably.

Sporadic and rare … but increasing?

Notwithstanding the apparently sporadic and relatively rare incidence of CBP in the UK (and elsewhere; the virus has a global distribution) anecdotal evidence suggested that cases of disease were increasing.

In particular, bee farmers were reporting increasing numbers of hives afflicted with the disease, and academic contacts overseas involved in monitoring bee health also reported increased prevalence.

Something can be rare but definitely increasing if you’re certain about the numbers you are dealing with. If you only have anecdotal evidence to go on you cannot be certain about anything very much.

If the numbers are small but not increasing there are probably other things more important to worry about.

However, if the numbers are small but definitely increasing you might have time to develop strategies to prevent further spread.

Far better you identify and define an increasing threat before it increases too much.

With research grant support from the UKRI/BBSRC (the Biotechnology and Biological Sciences Research Council) to the Universities of Newcastle (Principle Investigator, Prof. Giles Budge) and St Andrews, and additional backing from the BFA (Bee Farmers’ Association), we set out to determine whether CBPV really was increasing and, if so, what the increase correlated with (if anything).

This component of the study, entitled Chronic bee paralysis as a serious emerging threat to honey bees, was published in Nature Communications last Friday (Budge et al., [2020] Nat. Comms. 11:2164 https://doi.org/10.1038/s41467-020-15919-0).

The paper is Open Access and can be downloaded by anyone without charge.

There are additional components of the study involving the biology of CBPV, changes in virus virulence, other factors (e.g.environmental) that contribute to disease and ways to mitigate and potentially treat disease. These are all ongoing and will be published when complete.

Is chronic bee paralysis disease increasing?

Yes.

We ‘mined’ the National Bee Units’ BeeBase database for references to CBPV, or the symptoms associated with CBP disease. The data in BeeBase reflects the thousands of apiary visits, either by call-out or at random, by dedicated (and usually overworked) bee inspectors. In total we reviewed almost 80,000 apiary visits in the period from 2006 to 2017.

There were no cases of CBPV in 2006. In the 11 years from 2007 to 2017 the CBP cases (recorded symptomatically) in BeeBase increased exponentially, with almost twice as much disease reported in commercial apiaries. The majority of this increase in commercial apiaries occured in the last 3 years of data surveyed.

Apiaries recorded with chronic bee paralysis between 2006 and 2017.

BeeBase covers England and Wales only. By 2017 CBPV was being reported in 80% of English and Welsh counties.

During the same period several other countries (the USA, several in Europe and China) have also reported increases in CBPV incidence. This looks like a global trend of increased disease.

But is this disease caused by CBPV?

It should be emphasised that BeeBase records symptoms of disease – black, hairless bees; shaking/shivering bees, piles of bees at the hive entrance etc.

How can we be sure that the reports filed by the many different bee inspectors 11 are actually caused by chronic bee paralysis virus?

Or indeed, any virus?

To do this we asked bee inspectors to collect samples of bees with CBPV-like symptoms during their 2017 apiary visits. We then screened these samples with an exquisitely sensitive and specific qPCR (quantitative polymerase chain reaction) assay.

Almost 90% of colonies that were symptomatically positive for CBP were also found to have very high levels of CBPV present. We are therefore confident that the records of symptoms in the historic BeeBase database really do reflect an exponential increase of chronic bee paralysis disease in England and Wales since 2007.

Interestingly, about 25% of the asymptomatic colonies also tested positive for CBPV. The assay used was very sensitive and specific and allowed the quantity of CBPV to be determined. The amount of virus present in symptomatic bees was 235,000 times higher than those without symptoms.

Further work will be needed to determine whether CBPV is routinely present in similar proportions of ‘healthy’ bees, and whether these go on and develop or transmit disease.

Disease clustering

Using the geospatial and temporal (where and when) data associated with the BeeBase records we investigated whether CBPV symptomatic apiaries were clustered.

For example, in any year were cases more likely to be near other cases?

They were.

Across all years of data analysed together, or for individual years, there was good evidence for spatial clustering of cases.

We also looked at whether cases in one year clustered in the same geographic region in subsequent years.

They did not.

Clustering of CBPV – spatial and temporal analysis.

This was particularly interesting. It appears as though there were increasing numbers of individual clustered outbreaks each year, but that the clusters were not necessarily in the same geographic region as those in previous or subsequent years.

The disease appears somewhere, increases locally and then disappears again.

Apiary-level disease risk factors

The metadata associated with Beebase records is relatively sparse. Details of specific colony management methods are not recorded. Local environmental factors – OSR, borage, June gap etc. – are also missing. Inevitably, some of the factors that may be associated with increased risk are not recorded.

A relatively rare disease that is spatially but not temporally clustered is a tricky problem for which to define risk factors. Steve Rushton, the senior author on the paper, did a sterling job of analysing the data that was available.

The two strongest apiary-level factors that contributed to disease risk were:

  1. Commercial beekeeping – apiaries run by bee farmers had a 1.5 times greater risk of recording CBP disease.
  2. Importing bees – apiaries which had imported bees in the two preceding years had a 1.8 times greater risk of recording CBP disease.

Bee farming is often very different from amateur beekeeping. The colony management strategies are altered for the scale of the operation and for the particular nectar sources being exploited. For example, colonies may already be booming to exploit the early season OSR. This may provide ideal conditions for CBPV transmission which is associated with very strong hives and/or confinement.

Bee imports does not mean disease imports

There are good records of honey bees imported through official channels. This includes queens, packages and nucleus colonies. Between 2007 and 2017 there were over 130,000 imports, 90% of which were queens.

An increased risk of CBP disease in apiaries with imported bees does not mean that the imported bees were the source of the disease.

With the data available it is not possible to distinguish between the following two hypotheses:

  1. imported honey bees are carriers of CBPV or the source of a new more virulent strain(s) of the virus, or
  2. imported honey bees are susceptible to CBPV strain(s) endemic in the UK which they were not exposed to in their native country.

There are ways to tease these two possibilities apart … which is obviously something we are keen to complete.

All publicity is good publicity …

… but not necessarily accurate publicity 🙁

We prepared a press release to coincide with the publication of the paper. Typically this is used verbatim by some reporters whereas others ask for an interview and then include additional quotes.

Some more accurately than others 🙁

The Times, perhaps reflecting the current zeitgeist, seemed to suggest a directionality to the disease that we certainly cannot be sure of:

The Times

Its sister publication, The Sun, “bigged it up” to indicate – again – that bees are being wiped out.

The Sun

And the comments included these references to the current Covid-19 pandemic:

  • “Guess its beevid – 19. I no shocking”
  • “It’s the radiation from 5g..google it”
  • Local honey is supposed to carry antibodies of local virus and colds – it helps humans to eat the stuff or so they say. So it could be that the bees are actually infected by covid. No joke.

All of which I found deeply worrying, on a number of levels.

The Telegraph also used the ‘wiped out’ reference (not a quote, though it looks like one). They combined it with a picture of – why am I not surprised? – a bumble bee. D’oh!

The Telegraph

The Daily Mail (online) had a well-illustrated and pretty extensive article but still slipped in “The lethal condition, which is likely spread from imports of queen bees from overseas …”. The unmoderated comments – 150 and counting – repeatedly refer to the dangers of 5G and EMFs (electric and magnetic fields).

I wonder how many of the comments were posted from a mobile phone on a cellular data or WiFi network?

😉

Conclusions

CBPV is causing increasing incidence of CBP disease in honey bees, both in the UK and abroad. In the UK the risk factors associated with CBP disease are commercial bee farming and bee imports. We do not know whether similar risk factors apply outside the UK.

Knowing that CBP disease is increasing significantly is important. It means that resources – essentially time and money – can be dedicated knowing it is a real issue. It’s felt real to some bee farmers for several years, but we now have a much better idea of the scale of the problem.

We also know that commercial bee farming and bee imports are both somehow involved. How they are involved is the subject of ongoing research.

Practical solutions to mitigate the development of CBP disease can be developed once we understand the disease better.


Full disclosure:

I am an author on the paper discussed here and am the Principle Investigator on one of the two research grants that funds the study. Discussion is restricted to the published study, without too much speculation on broader aspects of the work. I am not going to discuss unpublished or ongoing aspects of the work (including in any answers to comments or questions that are posted). To do so will compromise our ability to publish future studies and, consequently, jeopardise the prospects of the early career researchers in the Universities of St Andrews and Newcastle who are doing all the hard work.

Acknowledgements

This work was funded jointly by BBSRC grants BB/R00482X/1 (Newcastle University) and BB/R00305X/1 (University of St Andrews) in partnership with The Bee Farmers’ Association and the National Bee Unit of the Animal and Plant Health Agency.

The scent of death

It’s late May. Outside it’s dark, so you’re trapped inside until sunrise. Inside it’s warm, dark and humid. You and your sisters are crowded together with barely enough space to turn around.

And your mother keeps laying more eggs … perhaps 2000 a day. If it wasn’t for the fact that about 2000 of your sisters perish each day you’d have no space at all.

Most of them die out in the fields. Missing in action.

I counted them all out and I didn’t count them all back, as the late Brian Hanrahan did not say in 1982 😉

But some die inside. And in the winter, or during prolonged periods of poor weather, your sisters all die inside.

Which means there’s some housekeeping to do.

Bring out your dead

Dead bees accumulating in the hive are a potential source of disease, particularly if they decompose. Unless these are removed from the colony there’s a chance the overall health of the colony will be threatened.

Not all bees die of old age. Many succumb to disease. The older bees in the colony may have a higher pathogen load, reinforcing the importance of removing their corpses before disease can spread and before the corpses decompose.

Corpses

Honey bees, like many other social insects, exhibit temporal polyethism i.e. they perform different tasks at different ages.

One of the tasks they perform is removing the corpses from the colony.

The bees that perform this task are appropriately termed the undertaker bees.

Gene Robinson in Cornell conducted observational studies on marked cohorts of bees. In these he identified the roles and activities of the undertaker bees. At any one time only 1-2% of the bees in the colony are undertakers 1.

These are ‘middle aged’ bees i.e. 2-3 weeks after eclosion, similar to guard bees. Although called undertakers, they do not exclusively remove corpses. Rather they are generalists that are more likely to remove the corpses, usually depositing them 50-100m from the hive and then returning.

They preferentially occupy the lower regions of the hive – presumably because gravity means the corpses accumulate there – where they also perform general hive cleansing roles e.g. removing debris.

Bees, like all of us, are getting older all the time. Some bees may spend only one day as undertakers before moving on to foraging duties. Presumably – I don’t think we know this yet – the time a bee remains as an undertaker is influenced by the colony’s need for this activity, the laying rate of the queen and, possibly, the numbers of other bees performing this role 2.

No no he’s not dead, he’s, he’s restin’!

Dead parrot

In Monty Python’s Dead Parrot sketch Mr. Praline (John Cleese) argues with the shop owner (Michael Palin) that the Norwegian Blue parrot he’d purchased was, in fact, dead.

The shop owner tries to persuade Mr. Praline that the parrot is resting.

Or stunned.

Or pining for the fjords.

The inference here is that it’s actually rather difficult to determine whether something is dead or not 3.

So if you struggle with an unresponsive parrot how do you determine if a bee is dead?

More specifically, how do undertaker bees in a dark, warm, humid hive determine that the body they’ve just tripped over is a corpse?

As opposed to a resting bee 4.

The scent of death

Almost forty years ago Kirk Visscher at Cornell studied necrophoresis (removal of the dead) in honey bees 5.

He noted that it had two distinct characteristics; it happened rapidly (up to 70 times faster than debris removal) and dead bees that were solvent-washed or coated in paraffin-wax were removed very much more slowly.

Kirk Visscher concluded that the undertaker bees “probably use chemical cues appearing very rapidly after the death of a bee” to identify the corpses.

Visscher studied honey bees, Apis mellifera. I’m not aware of any recent studies in A. mellifera that have better defined these ‘chemical cues’. However, a very recent preprint has been posted on bioRχiv describing how the closely related Eastern honey bee, Apis cerana, undertakers identify the dead.

As an aside, bioRχiv (pronounced bioarkive) is a preprint server for biology. Manuscripts published there have not been peer reviewed and will potentially be revised and/or withdrawn. They might even be wrong. Many scientists increasingly use bioRχiv to post completed manuscripts that have been submitted for publication elsewhere. The peer review and publication process is increasingly tortuous and long-winded. By posting preprints on bioRχiv other scientists can read and benefit from the study well before full publication elsewhere.

It’s also used as a ‘marker’ … we did this first 😉

The preprint on bioRχiv is Death recognition by undertaker bees by Wen Ping, submitted on the 5th of March 2020.

Odours and pongs

Death recognition in honey bees is rapid. Visscher demonstrated that a dead worker bee was usually removed within 30 minutes, well before it would have started producing the pong associated with the processes of decay.

Corpse recognition occurs in the dark and in the presence of lots of other bees. Logically, an odour of some sort might be used for identification. Both visual and tactile signals would be unlikely candidates.

In searching for the odour or chemical clues (the term used by Visscher), Ping made some assumptions based on prior studies in social insects. In Argentine ants a reduction in dolichodial and iridomyrmecin is associated with corpse recognition, and addition of these compounds (respectively a dialdehyde and a monoterpene) prevented necrophoresis.

Conversely, some social insects produce signals associated with death or disease. Dead termites give off a mix of 3-octanone, 3-octanol and the combination of β-ocimene and oleic acid production is a marker of diseased brood in honey bees.

What else could be assumed about the chemicals involved? Corpse removal is an individual effort. There’s only one pallbearer. Therefore the chemical, whatever it is, doesn’t need to be a recruitment signal (unlike the alarm pheromone for example).

Finally, the signal needs to operate over a very short range. There’s no point in flooding the hive with a persistent long-range chemical as that would make the detection of the corpse impossible.

Cuticular hydrocarbons

Cuticular hydrocarbons (CHC) are widely used in insect communication. They are long chain hydrocarbons (chemicals composed solely of carbon and hydrogen) that have many of the characteristics expected of a ‘death chemical’.

Nonacosane – a long chain CHC with 29 carbons and 60 hydrogen atoms

They are generally short-range, low volatility compounds. Honey bees use CHC’s for communication during the waggle dance and to distinguish colony mates by guard bees. They also have structural roles, being a major component of wax comb and, in the cuticle, they help maintain water balance in bees.

As would be expected from chemicals with a wide variety of roles, there’s a huge range of CHC’s. Taking all the above together, Wen Ping searched for CHC’s that functioned during necrophoresis.

Cool corpses and cuticular hydrocarbons

Wen studied undertakers removing segments of dead bees and determined that the chemical signal was most probably a component of the cuticle.

Living bees in his studies had a body temperature of ~44°C. In contrast, dead bees rapidly cooled to ambient temperatures. Wen demonstrated that corpse removal was significantly delayed if the corpses were warmed to ~44°C, but then occurred rapidly once they were allowed to cool. Finally, dead bees washed with hexane (which removes CHC’s) were removed even if the corpse was warm.

Taken together, these results suggest that a cuticular hydrocarbon that was produced and released from warm bees, but reduced or absent in cold bees, was a likely candidate for the necrophoresis signal.

But which one?

Gas chromatography

A gas chromatograph analyses volatile gases. Essentially gas vapour is passed through a thin coated tube and gaseous compounds of different molecular weights bind and elute at different times. It’s a very precise technique and allows all the components of a mixture to be identified by comparison with known standards.

Gas chromatography of volatiles from live (red) and dead (blue) bees.

Ping studied the volatile CHC’s in the airspace immediately surrounding dead bees or live bees using gas chromatography. There were some significant differences, shown by the absence of peaks in the blue trace of gases from the cold, dead bees. All of the peaks were identified and nine of the twelve peaks were CHC’s.

CHC’s with chain lengths of 27 or 29 carbons exhibited the greatest difference between live warm bees and cool dead bees and synthetic versions of these and the other CHC’s were tested to see which – upon addition – delayed the removal of dead bees.

Three had a significant impact in the dead bee removal assay – with chain lengths of 21, 27 and 29 carbons. These include the compounds heptacosane (C27H56)and nonacosane (C29H60).

Summary

The results section rather fizzles out in the manuscript posted to bioRχiv and I wouldn’t be surprised to see modifications to this part of the paper in a peer reviewed submission.

The overall story can be summarised like this. Live bees are warm and produce a range of CHC’s. Dead bees cool rapidly and some of the volatile CHC levels decrease in the immediate vicinity of the corpse. The undertaker bees specifically monitor the levels of (at least) heptacosane and nonacosane 6 as a means of discriminating between live and dead bees. Within 30 minutes of death local heptacosane and nonacosane levels have dropped below a level associated with life and the undertaker bee removes the corpse.

One final point worth making again. This study was conducted on Apis cerana. Our honey bees, A. mellifera, may use the same necrophoresis signals. Alternatively, they might use different chemicals in the same way.

Or they might do something else entirely.

Personally, I bet it’s a similar mechanism, potentially using different chemical.

There are mixed species colonies of A. mellifera and A. cerana. Do the undertakers only remove same-species corpses?

Global warming and hive cooling

The discussion of the bioRχiv paper raises two interesting points, both of which are perhaps a little contrived but still worth mentioning.

We’re living in a warming world.

Temperatures are rising

Dead bees cooling to ambient temperature lead to reduced CHC production. If global temperatures rise, so will the ambient temperature. Potentially this could decrease the reduction in the levels of CHC’s i.e. the dead bees might not look (er, smell!) quite so dead. This could potentially reduce corpse removal, with the concomitant potential for pathogen exposure.

I suspect that we’ll have much bigger problems to worry about than undertaker bees if the global temperatures rise that high …

But Wen also points out that the rise in global temperatures is also associated with more extreme weather, including very cold weather. Perhaps cold anaesthetised or weak bees will be prematurely removed from the hive under these conditions because their CHC levels have dropped below a critical threshold?

Finally, do dead bees lying on open mesh floors (OMFs) cool more rapidly and so trigger more efficient undertaking? Perhaps OMFs contribute more to hive hygiene than just allowing unwanted Varroa to drop through?


 

Time to deploy!

It’s early April. The weather is finally warming up and the crocus and snowdrops are long gone. Depending where you are in the UK the OSR may start flowering in the next fortnight or so.

All of which means that colonies should be expanding well and will probably start thinking of swarming in the next few weeks.

So … just like any normal season really.

Except that the Covid-19 pandemic means that this season is anything but normal.

Keep on keeping on

The clearest guidelines for good beekeeping practice during the Covid-19 pandemic are on the National Bee Unit website. Essentially it is business as usual with the caveats that good hygiene (personal and apiary) and social distancing must be maintained.

Specifically this excludes inspections with more than one person at the hive. Mentoring, at least the really useful “hands-on” mentoring, cannot continue.

A veil is no protection against aerosolised SARS-CoV-2. Don’t even think about risking it.

This means that there will be a lot of new beekeepers (those that acquired bees this year or late last season) inspecting colonies without the benefit of help and advice immediately to hand.

Mistakes will be made.

Queen cells will be missed.

Colonies will swarm 1.

Queen cells

Queen cells …

It’s too early to say whether the current restrictions on society are going to be sufficient to reduce coronavirus spread in the community. It’s clear that some are still flouting the rules. More stringent measures may be needed. For beekeepers who keep their bees in out apiaries, the most concerning would be a very restrictive movement ban. In China and (probably) Italy these measures proved to be effective, although damaging to beekeeping, so the precedent is established.

Many hives and apiaries are already poorly managed 2. I would expect that additional coronavirus-related restrictions would only increase the numbers of colonies allowed to “fend for themselves” over the coming season.

Which brings me back to swarming.

Swarmtastic

The final point of advice on the NBU website is specifically about swarms and swarm management:

You should use husbandry techniques to minimise swarming. If you have to respond to collect a swarm you need to ensure that you use the guidelines on social distancing when collecting the swarm. If that is not possible, then the swarm then should not be collected. Therefore trying to prevent swarms is the best approach. 

Collecting swarms can be difficult enough at the best of times 3. And cutouts of established colonies are even worse.

In normal years I always prefer to reduce the swarms I might be called to 4 by setting out bait hives.

Swarm recently arrived in a bait hive with a planting tray roof …

Let the bees do the work.

Then all you need do is collect them once they’re all neatly tucked away in a hive busy drawing comb.

This year, with who-knows-what happening next, I’ll be setting out more bait hives than usual with the expectation that there may well be additional swarms.

If they’re successful I’ll have more bees to deal with when the ‘old normal’ finally returns. If they remain unused then all I’ve lost is the tiny investment of time made in April to set them out.

Not just any dark box

I’ve discussed the well-established ‘design features’ of a good bait hive several times in the past. Fortunately the requirements are easy to meet.

  • A dark empty void with a volume of about 40 litres.
  • A solid floor.
  • A small entrance of about 10cm2, at the bottom of the void, ideally south facing.
  • Something that ‘smells’ of bees.
  • Ideally located well above the ground.

I ignore the last of these. I’d prefer to have an easy-to-reach bait hive to collect rather than struggle at the top of a ladder. If I wanted to do some vertically-challenging beekeeping I’d go out and collect more swarms 😉

So, ignoring the final point, what I’ve described is the nearly perfect bait hive.

Those paying attention at the back will realise that it’s also a nearly perfect description of a single brood National hive.

How convenient 🙂

All of my bait hives are either single National brood boxes or two stacked National supers. The box does need a solid floor and a crownboard and roof. If you haven’t got a spare solid floor you can easily build them from Correx 5 for a few pence.

Inside ...

Bait hive floor

Alternatively, simply tape down a piece of cardboard or Correx over the mesh of an open mesh floor 6. In some ways this is preferable as it’s convenient to be able to monitor Varroa levels after a swarm arrives.

Do not be tempted to use a nuc box as a bait hive. You can easily fit a small swarm into a brood box, but a really big prime swarm will not fit in a 5 frame nuc box.

Big swarms are better 🙂 7

More to the point, bees are genetically programmed to search for a void of about 40 litres, so many swarms will simply overlook your nuc box for a more spacious nest site.

What’s in the box?

No, this has nothing to do with Gwyneth Paltrow in Se7en.

How do you make your bait hive even more desirable to the scout bees that search out nest sites? How do you encourage those scouts to advertise the bait hive to their sister scouts? Remember, that it’s only once the scouts have reached a democratic consensus on the best local nest site that the bivouacked swarm will move in.

The brood box ideally smells of bees. If it has previously held a colony that might be sufficient.

Bait hive ...

Bait hive …

However, a single old, dark brood frame pushed up against one sidewall not only provides the necessary ‘bee smell’, but also gives the incoming queen space to immediately start laying 8.

You can increase the attractiveness by adding a couple of drops of lemongrass oil to the top bar of this dark brood frame. Lemongrass oil mimics the pheromone produced from the Nasonov gland. There’s no need to Splash it all over … just a drop or two, replenished every couple of weeks. I usually soak the end of a cotton bud, and lay it along the frame top bar.

Lemongrass oil and cotton bud

The old brood frame must not contain stores – you’re trying to attract scouts, not robbers.

The incoming swarm will be keen to draw fresh comb for the queen to lay up with eggs. Whilst you can simply provide some frames and foundation, this has two disadvantages:

  • the vertical sheets of foundation effectively make the void appear smaller than it really is. The scout bees estimate the volume by walking around the perimeter and taking short internal flights. If they crash into a sheet of foundation during the flight the box will seem smaller than it really is.
  • foundation costs money. Quite significant amounts of money if you are setting out half a dozen bait hives. Sure, they’ll use it but – like putting a new carpet into a house you’re trying to sell – it’s certainly not the deal-clincher.

No foundation for that

Rather than filling the box with about £10 worth of premium foundation, a far better idea is to use foundationless frames. Importantly these provide the bees somewhere to draw new comb whilst not reducing the apparent volume of the brood box.

If you’ve not used foundationless frames before, a bait hive is an ideal time to give them a try.

There are two things you should be on the lookout for. The first is that the bait hive is horizontal 9. Bees draw comb vertically down, so if the hive slopes there’s a good chance the comb will be drawn at an angle to the top bar.

And that’s just plain irritating … because it’s avoidable with a bit of care.

Bamboo foundationless frames

Bamboo foundationless frames

The second thing is that the colony needs checking as it starts to draw comb. Sometimes the bees ignore your helpful lollipop stick ‘starter strips’ and decide to go their own way, filling the box with cross comb.

Beautiful … but equally irritating 🙂

Final touches

For real convenience I leave my bait hives ready to move from wherever they’re sited to my quarantine apiary (I’ll deal with both these points in a second).

Wedge the frames together with a small block of expanded cell foam so that they cannot shift about when the hive is moved.

Foam block ...

Foam block …

And then strap the whole lot up tight so you can move them easily and quickly when you need to.

Bait hive location and relocation

Swarms tend to move relatively modest distances from the hives they, er, swarmed from. The initial bivouac is usually just a few metres away. The scout bees survey a wide area, certainly well over a mile in all directions. However, several studies have shown that bees generally choose to move a few hundred yards or less.

It’s therefore a good idea to have a bait hive that sort of distance from your own apiaries.

Or even tucked away in the corner of the apiary itself.

I’ve had bees move out of one box, bivouac a short distance away and then occupy a bait hive on a hive stand adjacent to the original hive.

It’s probably definitely poor form to position a bait hive a short distance from someone else’s apiary 😉

But there’s nothing stopping you putting a bait hive at the bottom of your garden or – whilst maintaining social distancing of course – in the gardens of friends and family.

If you want to move a swarm that has occupied a bait hive the usual “less than 3 feet or more than 3 miles” rule applies unless you move them within the first couple of days of arrival. Swarms have an interesting plasticity of spatial memory (which deserves a post of its own) but will have fully reorientated to the bait hive location within a few days.

So, if the bait hive is in grandma’s garden, but grandma doesn’t want bees permanently, you need to move them promptly … or move them over three miles.

Or move grandma 😉

Lucky dip

Swarms, whether dropped into a skep or attracted to a bait hive, are a bit of a lucky dip. Now and again you get a fantastic prize, but often it’s of rather low value.

The good ones are great, but even the poor ones can be used.

But there’s an additional benefit … every one that arrives self-propelled in your bait hive is one less reported to the BBKA “swarm line” or that becomes an unwelcome tenant in the eaves of a house 10.

As long as they’re healthy, even a bad tempered colony headed by a queen with a poor laying pattern, can usefully be united to create a stronger colony to exploit late season nectar.

Varroa treatment of a new swarm in a bait hive…

But they must be healthy.

Swarms will potentially have a reasonably high mite count and will probably need treating within a week of arrival in the bait hive 11. Dribbled or vaporised oxalic acid/Api-Bioxal would be my choice; it’s effective when the colony has no sealed brood 12 and requires a single treatment.

But swarms can bring even more unwelcome payloads than Varroa mites. If you keep bees in an area where foulbroods are established be extremely careful to confirm that the arriving swarm isn’t affected. This requires letting the colony rear brood while isolated in a quarantine apiary.

How do you know whether there are problems with foulbroods in your area? Register your apiary on Beebase and talk to your local bee inspector.

My bait hives go out in the second or third week of April … but I’m on the cool east coast of Scotland. When I lived in the Midlands they used to be deployed in early April. If you’re in the balmy south they should probably be out already 13.

What are you waiting for 😉 ?


 

Darwinian beekeeping

A fortnight ago I reviewed the first ten chapters of Thomas Seeley’s recent book The Lives of Bees. This is an excellent account of how honey bees survive in ‘the wild’ i.e. without help or intervention from beekeepers.

Seeley demonstrates an all-too-rare rare combination of good experimental science with exemplary communication skills.

It’s a book non-beekeepers could appreciate and in which beekeepers will find a wealth of entertaining and informative observations about their bees.

The final chapter, ‘Darwinian beekeeping’, includes an outline of practical beekeeping advice based around what Seeley (and others) understand about how colonies survive in the wild.

Differences

The chapter starts with a very brief review of about twenty differences between wild-living and managed colonies. These differences have already been introduced in the preceding chapters and so are just reiterated here to set the scene for what follows.

The differences defined by Seeley as distinguishing ‘wild’ and ‘beekeepers’ colonies cover everything from placement in the wider landscape (forage, insecticides), the immediate environment of the nest (volume, insulation), the management of the colony (none, invasive) and the parasites and pathogens to which the bees are exposed.

Some of the differences identified are somewhat contrived. For example, ‘wild’ colonies are defined fixed in a single location, whereas managed colonies may be moved to exploit alternative forage.

In reality I suspect the majority of beekeepers do not move their colonies. Whether this is right or not, Seeley presents moving colonies as a negative. He qualifies this with studies which showed reduced nectar gathering by colonies that are moved, presumably due to the bees having to learn about their new location.

However, the main reason beekeepers move colonies is to exploit abundant sources of nectar. Likewise, a static ‘wild’ colony may have to find alternative forage when a particularly good local source dries up.

If moving colonies to exploit a rich nectar source did not usually lead to increased nectar gathering it would be a pretty futile exercise.

Real differences

Of course, some of the differences are very real.

Beekeepers site colonies close together to facilitate their management. In contrast, wild colonies are naturally hundreds of metres apart 1. I’ve previously discussed the influence of colony separation and pathogen transmission 2; it’s clear that widely spaced colonies are less susceptible to drifting and robbing from adjacent hives, both processes being associated with mite and virus acquisition 3.

Abelo poly hives

50 metres? … I thought you said 50 centimetres. Can we use the next field as well?

The other very obvious difference is that wild colonies are not treated with miticides but managed colonies (generally) are. As a consequence – Seeley contends – beekeepers have interfered with the ‘arms race’ between the host and its parasites and pathogens. Effectively beekeepers have ‘weaken[ed] the natural selection for disease resistance’.

Whilst I don’t necessarily disagree with this general statement, I am not convinced that simply letting natural selection run its (usually rather brutal) course is a rational strategy.

But I’m getting ahead of myself … what is Darwinian beekeeping?

Darwinian beekeeping

Evolution is probably the most powerful force in nature. It has created all of the fantastic wealth of life forms on earth – from the tiniest viroid to to the largest living thing, Armillaria ostoyae 4. The general principles of Darwinian evolution are exquisitely simple – individuals of a species are not identical; traits are passed from generation to generation; more offspring are born than can survive; and only the survivors of the competition for resources will reproduce.

I emphasised ‘survivors of the competition’ as it’s particularly relevant to what is to follow. In terms of hosts and pathogens, you could extend this competition to include whether the host survives the pathogen (and so reproduces) or whether the pathogen replicates and spreads, but in doing so kills the host.

Remember that evolution is unpredictable and essentially directionless … we don’t know what it is likely to produce next.

Seeley doesn’t provide a precise definition of Darwinian beekeeping (which he also terms natural, apicentric or beefriendly beekeeping). However, it’s basically the management of colonies in a manner that more closely resembles how colonies live in the wild.

This is presumably unnnatural beekeeping

In doing so, he claims that colonies will have ‘less stressful and therefore more healthful’ lives.

I’ll come back to this point at the end. It’s an important one. But first, what does Darwinian mean in terms of practical beekeeping?

Practical Darwinian beekeeping

Having highlighted the differences between wild and managed colonies you won’t be surprised to learn that Darwinian beekeeping means some 5 or all of the following: 6

  • Keep locally adapted bees – eminently sensible and for which there is increasing evidence of the benefits.
  • Space colonies widely (30-50+ metres) – which presumably causes urban beekeepers significant problems.
  • Site colonies in an area with good natural forage that is not chemically treated – see above.
  • Use small hives with just one brood box and one super – although not explained, this will encourage swarming.
  • Consider locating hives high off the ground – in fairness Seeley doesn’t push this one strongly, but I could imagine beekeepers being considered for a Darwin Award if sufficient care wasn’t taken.
  • Allow lots of drone brood – this occurs naturally when using foundationless frames.
  • Use splits and the emergency queen response for queen rearing i.e. allow the colony to choose larvae for the preparation of new queens – I’ve discussed splits several times and have recently posted on the interesting observation that colonies choose very rare patrilines for queens.
  • Refrain from treating with miticides – this is the biggy. Do not treat colonies. Instead kill any colonies with very high mite levels to prevent them infesting other nearby colonies as they collapse and are robbed out.

Good and not so good advice

A lot of what Seeley recommends is very sound advice. Again, I’m not going to paraphrase his hard work – you should buy the book and make your own mind up.

Sourcing local bees, using splits to make increase, housing bees in well insulated hives etc. all works very well.

High altitude bait hive …

Some of the advice is probably impractical, like the siting of hives 50 metres apart. A full round of inspections in my research apiary already takes a long time without having to walk a kilometre to the furthest hive.

The prospect of inspecting hives situated at altitude is also not appealing. Negotiating stairs with heavy supers is bad enough. In my travels I’ve met beekeepers keeping hives on shed roofs, accessed by a wobbly step ladder. An accident waiting to happen?

And finally, I think the advice to use small hives and to cull mite-infested colonies is poor. I understand the logic behind both suggestions but, for different reasons, think they are likely to be to the significant detriment of bees, bee health and beekeeping.

Let’s deal with them individually.

Small hives – one brood and one super

When colonies run out of space for the queen to lay they are likely to swarm. The Darwinian beekeeping proposed by Seeley appears to exclude any form of swarm prevention strategy. Hive manipulation is minimal and queens are not clipped.

They’ll run out of space and swarm.

Even my darkest, least prolific colonies need more space than the ~60 litres offered by a brood and super.

Seeley doesn’t actually say ‘allow them to swarm’, but it’s an inevitability of the management and space available. Of course, the reason he encourages it is (partly – there are other reasons) to shed the 35% of mites and to give an enforced brood break to the original colony as it requeens.

These are untreated colonies. At least when starting the selection strategy implicit in Darwinian beekeeping these are likely to have a very significant level of mite infestation.

These mites, when the colony swarms, disappear over the fence with the swarm. If the swarm survives long enough to establish a new nest it will potentially act as a source of mites far and wide (through drifting and robbing, and possibly – though it’s unlikely as it will probably die – when it subsequently swarms).

A small swarm

A small swarm … possibly riddled with mites

Thanks a lot!

Lost swarms – and the assumption is that many are ‘lost’ – choose all sorts of awkward locations to establish a new nest site. Sure, some may end up in hollow trees, but many cause a nuisance to non-beekeepers and additional work for the beekeepers asked to recover them.

In my view allowing uncontrolled swarming of untreated colonies is irresponsible. It is to the detriment of the health of bees locally and to beekeepers and beekeeping.

Kill heavily mite infested colonies

How many beekeepers reading this have deliberately killed an entire colony? Probably not many. It’s a distressing thing to have to do for anyone who cares about bees.

The logic behind the suggestion goes like this. The colony is heavily mite infested because it has not developed resistance (or tolerance). If it is allowed to collapse it will be robbed out by neighbouring colonies, spreading the mites far and wide. Therefore, tough love is needed. Time for the petrol, soapy water, insecticide or whatever your choice of colony culling treatment.

In fairness to Seeley he also suggests that you could requeen with known mite-resistant/tolerant stock.

But most beekeepers tempted by Darwinian ‘treatment free’ natural beekeeping will not have a queen bank stuffed with known mite-resistant mated queens ‘ready to go’.

But they also won’t have the ‘courage’ to kill the colony.

They’ll procrastinate, they’ll prevaricate.

Eventually they’ll either decide that shaking the colony out is OK and a ‘kinder thing to do’ … or the colony will get robbed out before they act and carpet bomb every strong colony for a mile around.

Killing the colony, shaking it out or letting it get robbed out have the same overall impact on the mite-infested colony, but only slaying them prevents the mites from being spread far and wide.

And, believe me, killing a colony is a distressing thing to do if you care about bees.

In my view beefriendly beekeeping should not involve slaughtering the colony.

Less stress and better health

This is the goal of Darwinian beekeeping. It is a direct quote from final chapter of the book (pp286).

The suggestion is that unnatural beekeeping – swarm prevention and control, mite management, harvesting honey (or beekeeping as some people call it 😉 ) – stresses the bees.

And that this stress is detrimental for the health of the bees.

I’m not sure there’s any evidence that this is the case.

How do we measure stress in bees? Actually, there are suggested ways to measure stress in bees, but I’m not sure anyone has systematically developed these experimentally and compared the stress levels of wild-living and managed colonies.

I’ll explore this topic a bit more in the future.

I do know how to measure bee health … at least in terms of the parasites and pathogens they carry. I also know that there have been comparative studies of managed and feral colonies.

Unsurprisingly for an unapologetic unnatural beekeeper like me ( 😉 ), the feral colonies had higher levels of parasites and pathogens (Catherine Thompson’s PhD thesis [PDF] and Thompson et al., 2014 Parasite Pressures on Feral Honey Bees). By any measurable definition these feral colonies were less healthy.

Less stress and better health sounds good, but I’m not actually sure it’s particularly meaningful.

I’ll wrap up with two closing thoughts.

One of the characteristics of a healthy and unstressed population is that it is numerous, productive and reproduces well. These are all characteristics of strong and well-managed colonies.

Finally, persistently elevated levels of pathogens are detrimental to the individual and the population. It’s one of the reasons we vaccinate … which will be a big part of the post next week.


 

Which is the best … ?

It’s (slowly) approaching the start of the beekeeping season.

From draughty church halls across the land newly trained beekeepers are emerging (or eclosing, to use the correct term), blurry-eyed from studying their Thorne’s catalogues, desperate to get their hands on some bees and start their weekly inspections.

Their enthusiasm is palpable 1.

The start of the beekeeping season, any season, after the long winter is always a good time. Longer days, better weather, more light 🙂 . For current beekeepers we can stop fretting over stores or winter losses. The long days with plentiful forage are getting nearer. We’ll soon be doing inspections in our shirtsleeves and thinking about swarm prevention.

New beekeepers, those who haven’t had to worry about Storm Ciara wrecking their apiaries or subsequent flooding washing hives away, simply want to get started as soon as possible.

Moving to higher ground ...

Moving to higher ground …

But, of course, they want to do things properly.

They don’t want to cut corners, they don’t want to skimp or make false economies. They want the best for their (as yet, non-existent) bees.

They’re committed and serious and determined to make a success of beekeeping … and get a great honey crop.

It needs to be great as they’ve already ‘promised away’ half of it to friends and family 🙂

Which is the best …?

If you look on the online beekeeping discussion fora, or questions to the BBKA Q&A monthly column or listen to discussions at local association meetings, many start with the words “Which is the best …”.

Which is the best hive, the best strain of bees, the best fuel for your smoker etc.

These questions reflect a couple of things:

  1. A lack of experience coupled with an enthusiasm to properly care for their charges.
  2. The generally misguided belief that these things make any substantive difference to the welfare or productivity of the bees.

Neither of these are criticisms.

All beekeepers should want the best for their bees.

Inexperienced beekeepers don’t know what works and what does not work, but they want to ensure that – whatever they do – the bees do not suffer (or fail to thrive).

They want the best bees, presumably defined as those that are calm, frugal, populous and productive and they want the best hive so these bees are warm enough in winter and cool enough in summer, or have enough space, or are easiest to manipulate, or best resembles a tree trunk.

And the smoker fuel should be the best so that it’s easy to light, never goes out and calms the bees quickly.

The best smoker fuel

Logic dictates that if there was a ‘best’ smoker fuel then almost everyone would be using it.

The septuagenarian ‘expert’ with 50 years experience would have said “Stuff your smoker with XYZ” when describing hive inspections on the beginners course. Other experienced beekeepers around the room would nod sagely and that would be the end of the matter.

If a beginner were to ask “Why don’t you use hessian rather than XYZ?” over a cuppa and a digestive afterwards there would be an awkward silence and a simple “Because XYZ is the best smoker fuel you can use” response.

The group would then move on to talk about something else.

Fuel bucket

XYZ …

And that happens … precisely never.

What actually happens is that eight beekeepers (with varying levels of expertise) contribute eleven different opinions of their personal view of the ‘best’ smoker fuel.

The only thing vaguely in common in these opinions is that some of the recommended fuels burn.

Note that I said ‘some’ 😉

The point I’m trying to make is that the ‘best’ smoker fuel does not exist. It’s what works for you when you need it … dried horse manure (yes, really), grass, wood chips, Thorne’s cardboard packaging, rotten dried wood etc.

It’s what’s in your bag, it’s what you carefully collected last month, it’s what you find in the car glove compartment when you can’t find anything else.

If it burns – ideally slowly and gently – producing good amounts of smoke, if it’s easy to light, light to carry, stays lit and is available when you need it, it’ll do.

The best hive

I’ve previously discussed the ridiculously wide range of hives and frames available to UK beekeepers.

Knowing that, or spending just half an hour perusing the Thorne’s catalogue, shows that there is clearly no ‘best’ hive. Any, and probably all, of the hives work perfectly satisfactorily. In the right conditions and with sympathetic and careful beekeeping all are capable of housing a colony securely and productively.

It’s the hive type that is compatible with those used by your mentor 2, it’s the type you have a stack of in the corner of the shed, it’s what you can borrow at short notice when you’ve run out of broods or supers.

It’s what’s available in the end of season sales or it’s what you started with (or your mother started with) and it ‘just works’.

If there was a best hive type, or hive tool or smoker fuel the Thorne’s catalogue would be about 3 pages long.

It’s not, it’s approaching 100 pages in length, with 12 pages of hive types alone (including a nice looking Layens hive). The 2020 catalogue has even more hive tools than the seventeen I counted in 2019 🙁

If there’s no ‘best’, will anything do?

Just because there might not be the perfect hive, smoker fuel or hive tool does not mean that it doesn’t matter what you use.

There are some that are unsuitable.

Smoker fuel that doesn’t stay lit, or that burns too fiercely. Hive tools with blunt edges, or that rust badly and are difficult to sterilise, or that bend 3. Hives with incorrect dimensions, ill-fitting floors, overly fussy designs or a host of other undesirable ‘features’.

Just because there’s no single best whatever definitely does not mean that anything will do.

Anthropocentrism

But, before we move on, note that all the things I used to define a smoker fuel or hive as ‘the best’ were anthropocentric 4 criteria.

It’s what suits us as beekeepers.

And, since there are a wide range of beekeepers (by education, age, height, intellect, shoe size, strength, wealth, petty likes and dislikes etc.) there is inevitably a very wide choice of stuff for beekeeping.

Which also emphasises the irrelevance of the ‘best type of ‘ question.

The full version of the question is “Which is the best type of hive tool for beekeepers” 5.

But what’s best for the bees?

None, or any, of the above.

Clearly no single hive tool is better than any other as far as the bees are concerned.

Take your pick ...

The bees do not care …

Likewise, as long as the smoker fuel generates cool, not-too-acrid, smoke, as far as the bees are concerned it’s just smoke. It masks the smell of the alarm pheromones and encourages the bees to gorge on honey, so they remain calm. Used judiciously, which is nothing to do with the fuel and everything to do with the beekeeper, one type of smoker fuel should be as good as any other.

And the same thing applies to hives. Assuming they’re secure, wind and watertight, large enough to fill with stores, have a defendable entrance and proper bee space around the frames, they’ll suit the bees perfectly well.

Think about the trees that wild-living bees naturally choose … do they prefer oak or lime, tall chimney-like cavities or largely spherical hollows?

Oak … preferred by bees. Or not.

Do they do better in one species of tree over another, one shape of space over another?

No.

Doing better …

How do we tell if the bees are ‘doing better’ anyway?

We can’t ask them.

We cannot, despite the assurances of the so-called bee-centric or bee-friendly beekeepers, tell whether they’re happy or not.

I’m a very bee-friendly beekeeper, but I don’t anthropomorphize and attribute feelings like happy or sad to my bees 6.

I determine whether a colony is doing well (or better) by very similar criteria to those you would use to judge whether a colony in a tree was flourishing.

Are they building up well, are they storing sufficient pollen and honey stores, is there overt disease, are they going to swarm?

The hive tool, smoker fuel or any one of a dozen or more hive types, have little or no influence on these measurable definitions of ‘doing well’.

What is it that determines the success or otherwise of a colony?

Essentially it comes down to two things – forage and colony health.

Bees ‘do well’ when they have ample and varied forage and when they are (largely) free of disease 7.

A healthy colony with ample forage will do better irrespective of the hive tool, hive type or smoker fuel used. You could house them in a plastic dustbin, prize the lid off with a screwdriver and waft a smouldering egg box across the entrance and they’ll still ‘do well’.

Egg box smoker

Smouldering egg box …

Conversely, put a disease-weakened colony in an area of poor forage and they’ll do badly (probably very badly) … again irrespective of the hive type, tool or smoker fuel.

Good forage does not just mean lots of it (though that helps). It means early-season pollen for colony build-up, it means late-season nectar and pollen to help develop a strong population of winter bees, it means a varied diet and it means season-long availability.

A healthy colony is one that has no overt disease. It has low levels of parasites and pathogens 8 and is able to survive periods of nectar shortages without succumbing to disease. In addition, it is resilient and genetically diverse.

And so back to those eclosing trainee beekeepers … the real ‘best’ questions they should be asking are:

  • Where is the best place to site my colonies to ensure good, season-long forage availability?
  • How to I best keep my colonies as disease-free as possible so that they can exploit that forage?

Focusing on these questions will help ensure the honey crop really is great so you can provide all those friends and family with the jars they have been promised 😉

Exceptions to the above

Inevitably there are exceptions.

It wouldn’t be beekeeping without qualifications and caveats.

The best bees are almost certainly local bees. There are several studies that demonstrate locally-adapted bees do better than imported bees. This does not mean that imported (and not necessarily from abroad) bees cannot do well. I’ve discussed some of these studies recently.

Finally, whilst the smoker fuel is irrelevant, the smoker is not.

The best smoker is the large Dadant smoker. The small Dadant is pretty good, but the large one is the bee’s knees 9.

Large Dadant smoker

I know, because my happy bees told me so 🙂


 

 

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 ± 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 – at 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 …


 

Questions & Answers

One of the challenging things about beekeeping is that the season can be both confusing and entertaining in equal measure.

It’s entertaining because it’s always a little bit different from the seasons that have preceded it. The environment changes. There’s an early spring, or late frosts, a drought, a monsoon or the local farmer changes from one strain of OSR to another.

Sometimes you get all of those in a single season … or month.

Mainly dry ...

Mainly dry …

But not only does the environment change, so do your bees. Inevitably your queens will be replaced over the years. In turn, they influence the performance of the colony. Your virgins fly off to the drone congregation areas where they mate with the ‘bad boys’ from colonies run by a nearby beekeeper with much thicker gloves and a fleece under his beesuit 🙁

Mayhem ensues. Inspections get a whole lot less fun. Quickly.

Or you collect a swarm headed by a fecund queen who busies herself producing calm, prolific, frugal and productive workers.

The colony gets bigger. And bigger. It shows no signs of swarming.

As you add the fourth super you feel like you’ve really cracked this beekeeping lark.

Sorted 🙂

But these things also make beekeeping incredibly confusing to the newcomer.

If you take a calendar-centric view there is no right answer to ‘When will the colony swarm?’ or ‘Is this the right time to treat for mites?’ or ‘Should I remove the supers now?’.

And many beginners do have a calendar-based viewpoint. It’s so much easier to prepare if you’re told that swarming starts in the third week of May and the supers should be removed at the end of August.

Not only is that easier to understand, but the telltale signs that the bees produce aren’t – for a beginner – very good at telling tales.

The first half-hidden charged queen cell, a reduced laying rate, the reduction in loaded returning foragers etc.

Play cup or queen cell?

Play cup or are they planning their escape …?

But, for me, at least half of the enjoyment is deciphering these signs and working out what the colony is doing, or going to do.

And therefore, what I should be doing.

Questions and answers

Most of this is observation, interspersed with a bit of record keeping and sprinkled with some ‘best guesses’.

If you keep asking the (right) questions you will slowly but surely start finding the answers.

Are they running out of space, making more play cups, and slimming the queen down for the great escape?

But many of these things are too subtle for beginners overwhelmed by the difficulty in just finding the queen amongst 38,789 of her daughters.

Inevitably this means that beginners – quite rightly – ask other beekeepers lots of questions.

I did.

I still do.

And in this increasingly connected world, some of those questions take the form of internet searches.

And some of these questions pop up as search terms on this site.

Mites

Willie Wonka meme

Many of these queries are about mite management:

  • best time to treat for varroa in honey bees?
  • should bees be treated for mites in spring?
  • use apiguard in june?
  • oxalic acid to treat varroa can i do it this week?
  • when to treat bees with oxalic acid in arkansas?

Very specific questions, very calendar-centric. There are hundreds more queries like these 1.

A correct answer requires an understanding of the biology of the mite and an appreciation of the state of the hive.

Neither necessarily involves the calendar. Both can be acquired with a little homework and good observation. However, the very fact that ~25% of queries are about mite management emphasises that many struggle with this aspect of beekeeping.

I remain convinced that the biggest challenge new beekeepers face is how to effectively manage mites. Without proper mite management your colonies will perish.

If you lose your colonies every winter you soon get disheartened.

The easiest way to properly control mite numbers is with chemicals.

It’s what I do.

Returning a marked and clipped queen

However, it’s not the only way.

Excellent beekeeping, selective rearing of mite-tolerant colonies (or of attenuated viruses!) and yet more excellent beekeeping – coupled with a favourable environment – may mean you can keep colonies without chemical intervention, and without excessive losses 2.

All beginners lack the necessary experience to achieve this. Most lack the ability to learn the skills quickly enough to save their colonies and the majority probably live in areas that are unsuitable.

Most importantly, many beginners aren’t resilient enough to ‘learn the hard way’. They believe the (largely incorrect) statements about the evils of treatment, they want their bees to be ‘healthy and happy’ 3, they like the sound of the term biodynamic 4 … but they cannot cope with losing their stocks every single winter through disease and starvation.

So they give up.

Learn to keep bees … then learn (again, using the years of knowledge already accumulated) to keep them without chemical intervention if you want. Not the other way round.

Read all you can – here and elsewhere – but remember that nothing is as valuable as time spent observing your bees.

Technical queries

These are the sorts of questions that probably can be easily answered 5.

Remembering of course that there are usually at least two correct answers for every question, and any number of incorrect ones.

  1. honey warming cabinet plans
  2. how long does it take bees to chew through newspaper?
  3. what is the chance of a queen being left in my hive when i have just lost a huge swarm?
  4. alighting board angle
  5. where and how to set up bait hives?

My honey warming cabinet is one of the most useful things I’ve built for my beekeeping and the pages that first describe it, the plans and its use, remain some of the most popular on this site.

The answer to Q2 obviously depends upon how many sheets of newspaper are involved.

I think we all know the answer to Q3 and it’s not going to make the questioner happy 😉

It’s very rare that you can provide an absolute definitive answer in beekeeping. However, after many years of exhaustive, well-controlled and independently verified trials I have unequivocally shown that the answer to Q4 is 47.7°.

47.7° precisely

Not more, not less.

Remembering of course that a landing (alighting) board isn’t actually needed at all 😉

Tom Seeley has done the definitive studies on bait hives (Q5). He clearly describes the ‘where’. My recommendations are rather more pragmatic. It’s easier to monitor and move bait hives if they’re not 5 metres above the ground.

Miscellaneous or just weird

And then there are lots of queries that are simply amusing typos, nonsensical or just odd. My favourites this year are:

  1. maxant crank mechanism
  2. langtorthe eke
  3. how to wear rigger boots?

I’ve no idea how the first of these landed up on the apiarist.org as it’s a term I’ve never used. The middle query (Q2) is a typical typo. It’s an obvious one, but it constantly amazes me how good fuzzy matching algorithms are these days.

Q3 is about beekeeping footwear. My last pair of rigger boots were abandoned years ago when the lining fell apart and they eventually turned my feet to a bloody pulp.

How to wear them?

I wore mine while hobbling. It’s not something I’d recommend.

I now wear Muck boots – specifically the now discontinued Edgewater II short boots – which are lightweight, very comfortable and fully waterproof. No steel toe cap, but I never drop full supers.

Oops ...

Oops …

Well, almost never.

Questions and comments

Not all questions originate in internet searches. Many come via the comments sections at the end of most posts. Most of these are both welcomed and useful; they allow me to clarify things that I’d presented confusingly, or they provide an opportunity to expand on parts of the post.

The numbers of comments have increased significantly this year.

More words and more comments

This increase probably reflects the increased readership (and page accesses) of the site.

Alternatively it might mean the writing is getting worse as the comment numbers correlate with the increased length of posts 🙁

I try and answer as many comments/questions as I can. Many make very salient points and I’m very grateful for those who take the time to comment, either to correct me, to seek clarification or to provide their own insight on the topic.

I ignore those that are dogmatically stupid or just plain wrong. My prerogative. There’s enough bad advice on the internet without propagating more.

I apologise to those who comment via Facebook or Twitter. I almost exclusively use both for promoting posts made here 6. Both generate a lot of traffic to this site but I simply don’t have time (or interest) to use them interactively.

If you want to contact me do so via the comments section or the, aptly named, contact form.

More Readers’ Questions

Which, in a rather circuitous way, brings me to the Readers’ Questions Answered column in the BBKA News. I was asked to tackle these a few months ago and January and February are already written 7.

BBKA News Readers’ Questions Answered proofs

The BBKA News is the monthly newsletter of the British Beekeepers Association. It has a circulation of ~25,000. Each year a different victim expert mug contributor prepares the answers. I’m taking over from Bob Smith, NDB from Medway BKA who did an excellent job and will be a hard act to follow. Some of the previous contributors have been anonymous which might have been a sensible option, but it’s too late for me now.

My family joke that I’m now an agony aunt for beekeepers.

I discussed this with Calum, a regular contributor to the comments section of these pages, who provided (as usual) some very sage advice, including “Bees put up with a lot of sh1t from beekeepers”. I don’t think the BBKA will want to use that as my strapline but it certainly sums things up pretty accurately.

Happy New Year … may your queens be well mated, your mite numbers low, your supers heavy and may your prime swarms be in my bait hives  🙂


 

Rinse and repeat

Midwinter mite treatment is no substitute for a properly applied late summer treatment that protects your all important winter bees. However, you also need to control mites in the winter or there is a good chance their numbers will reach damaging levels the following season 1.

Mid September

Late summer treatment and no winter treatment – mite levels in red.

OA (oxalic acid-containing) treatments are the ones to use in midwinter (e.g. Api-Bioxal). These can be trickled in syrup onto each seam of bees or they can be vaporised (sublimated), effectively coating everything in the hive with a very fine dusting of crystals.

Trickling damages open brood whereas sublimation is exceedingly well-tolerated by the colony.

If you are certain the colony is broodless then trickling is faster 2 and – because you don’t need power or any more PPE 3 than a pair of gloves – much easier.

If the ambient temperature is consistently below ~6°C and I know the colony is broodless I usually trickle. If the temperature is higher and/or I’m uncertain about whether there is brood present I usually vaporise.

I watch the weather and treat after the first prolonged cold spell of the winter.

Experience over the last few years suggests this is when colonies are most likely to be broodless.

Most likely is not the same as certain 🙁

Count the corpses

After treating I closely monitor the mite drop over several days. I use white Correx Varroa trays that slide underneath the open mesh of my kewl floors.

Easy counting ...

Easy counting …

I don’t count the mites every day, but I do try and count the day after treatment and 2-4 days later. I record the mite drop per hive and, over time, look for two things:

  1. The cumulative mite drop. This indicates the original infestation level of the hive. Usually it’s in the range 10-75 mites (total) for my colonies in midwinter, but – as you’ll see – it can be much higher.
  2. The speed with which the daily mite drop falls to a low single-digit average. OA treatment is very effective at killing phoretic mites. If there’s a continuing high level of mite drop it suggests that more are getting exposed over time.

In my experience, vaporised OA often results in a greater mite drop 24-48 hours post-treatment rather than in the first 24 hours 4. After that I expect (hope) the daily mite drop tails off very quickly.

Vaporised OA remains effective in the hive for several days. Randy Oliver reports studies by Radetzki who claims it remains effective for up to three weeks. I think this is an overestimate but I’m sure it continues working well for four to five days.

OA, whether vaporised or trickled, on broodless colonies is 90-95% effective i.e. if there were 100 mites in the colony you should expect as few as 5 remain after treatment.

Four to five days after the initial treatment I eyeball the numbers across all the hives in an apiary and look at the profile of the mite drop.

Mite drop profiles

I couldn’t think of a better term for this. Essentially, it’s the shape of a graph of mites dropped per day after treatment.

I don’t usually draw the graph – I have a life – but I do look carefully at the numbers.

Here are a couple of sketched graphs showing what I mean. Days are on the horizontal (X) axis, dead mites per day are on the vertical (Y) axis. Treatment applied on day 0. No count (yet) on day 6.

Mite drop profile – this is what you want

In the graph above there are high(er) levels of dropped mites on the first day or two after treatment, but levels thereafter drop to a basal level of perhaps 1-4 mites per day.

Each time I count the mites I clean the Varroa tray (the rinse in the title of the post).

Assuming the day 5 mite drop is very low, the profile above is what I’m looking for. It shows that treatment has worked and no repeat is necessary.

The profile below is much less promising 5.

Mite drop profile – this suggests additional treatment is needed

In this graph (above) the mite drop remains high every day after treatment. Sometimes they even increase over time.

If you assume treatment is equally effective – say 90%+ – on the five days after treatment 6 this must mean that there are mites being killed on days 4 and 5 that were not exposed to treatment on the earlier days.

How can this be?

The most likely explanation is that the colony had some sealed brood that has emerged in the days following treatment, exposing previously ‘hidden’ mites to the miticide.

It’s good that they’ve perished, but are there more hiding? How do you tell?

Enough of my hand drawn idealised graphs with no real numbers … what about some actual data?

Real world data

The graph below shows data for seven colonies in a single apiary. All were treated with Apivar in late summer. All were treated with a vaporised oxalic acid-containing treatment on the 28th of November. 

Mite drop profiles – real world data

I counted the mite drops on the 29th (T+1), the 2nd (T+4) and 3rd (T+5). The figures for 30th to the 2nd were averaged, which is why the bars are all the same height.

  • Colonies 3 and 6 had very low mite levels. Though not the lowest in the apiary 🙂
  • Colonies 2 and 7 had pretty good mite drop profiles, with low single-digit numbers on day T+5. None of these four colonies (2, 3, 6, 7) need treating again.
  • Colonies 1 and 5 have high mite levels 7 and – despite the pretty good levels on T+5 in colony 1 – were both re-treated.
  • Colony 4 was also treated again as the profile was flat and I suspected they had low levels of mites but were rearing brood..

And repeat

Note: The instructions for Api-Bioxal specifically state that the maximal dose of 2.3g/hive should be made in a single administrations with only one treatment per yearPrior to the VMD licensing and approval of Api-Bioxal there was effectively tacit approval for beekeepers to use unadulterated oxalic acid by trickling or vaporisation, without any particular limitations on frequency of usage.

It’s worth stressing that you should not repeat oxalic acid trickling 8.

Here is some real data for repeat treatments of another colony in the same apiary.

Repeat treatment for brood-rearing colony

The average mite drop per day over the first 5 days was ~60. This justified an additional treatment. Over the next 6 days 9 the average drop was ~20. I considered a third application was needed after which the mite drop per day was in the low single digits.

And again

Repeated treatment is needed if there is sealed brood in the colony.

The likelihood is that two additional treatments will be required.

Why two?

Here’s a reminder of the development cycle of the Varroa mite in developing worker or drone brood.

Repeated oxalic acid vaporisation treatment regime.

Worker brood occupies capped cells for 12 days (days 10 – 21 of development, shown above). Vaporised oxalic acid-containing treatments show a drop in efficacy after 4-5 days 10.

Therefore, to cover a complete cycle of capped brood, you need 3 x 5 day treatments to be sure no mites emerge without them being greeted with a lethal dose of something really, really unpleasant 😉

There should be no drone brood in your winter hives 11 but, if there was, 3 x 5 day treatments should just be enough to cover the complete cycle of capped drone brood as well. However, a fourth treatment might be needed.

Note (again): The instructions for Api-Bioxal specifically state that the maximal dose of 2.3g/hive should be made in a single administrations with only one treatment per year

Not all hives are equal

There are 15 hives in the apiary containing the bee shed. Colony 1 had just about the highest mite levels. However, as shown in one of the graphs above, adjacent colonies can have markedly different mite levels.

There is no clear correlation between mite drop after treatment and colony size. Colony 1 is a double brood monster, but the others in the bee shed are all single brood 10 and 11 frame Nationals 12.

Some colonies need repeated treatment, others did not.

To maximise efficient treatment and minimise unnecessary miticide usage it is necessary to monitor all the colonies.

It’s also worth noting that monitoring only a single hive in an apiary may be misleading; compare colonies 1 and 6 above in the graph of real data from the bee shed.

This monitoring takes just a few minutes. I usually do it after work. In the bee shed this is easy as I now have LED lighting and it’s nice and dry.

Easy conditions to count mites

In my out apiaries I have to do it by headtorch … under an umbrella if it’s raining 🙁

Checking mite drop by torchlight

That’s the last job of the winter completed … time now to review the season just gone and plan for next year.


Colophon

Rinse and repeat

Rinse and repeat is a truncation of instructions often found on the side of shampoo bottles – Lather, rinse and repeat. Other than potentially resulting in an endless loop of hair washing, it also means that a process is (or needs to be) repeated.

In The Plagiarist by Benjamin Cheever, a marketing executive becomes an industry legend by adding one word – REPEAT – to shampoo bottles. He doubles sales overnight.

For Varroa treatment the instructions should be amended to Repeat if necessary … and note again the instructions on Api-Bioxal which, at the time of writing, is the only oxalic-acid containing VMD approved miticide that can be administered by vaporisation.

 

More local bee goodness?

Before the wind-down to the end of the year and the inevitable review of the season I thought I’d write a final post apparently supporting the benefits of local bees. This is based on a recently published paper from the USA 1 that tests whether local bees perform better than non-local stocks.

However, in my view the study is incomplete and – whilst broadly supportive – needs further work before it can really be seen as an example of better performing local bees. I suspect there’s actually a different explanation for their results … that also demonstrates the benefits of local bees.

This is a follow-up to a post three weeks ago that provided evidence that:

  1. Colonies derived from different geographic regions show physiological adaptations (presumably reflecting underlying genetic differences) that seem pretty logical e.g. bees from Saskatchewan express more proteins involved in heat production, whereas Hawaiian bees show higher levels of protein turnover (which would make sense if they had evolved locally to have high metabolic rates).
  2. In a study by Büchler, European colonies survived better overwinter in their local environment; a fact subsequently attributed to the colonies being stronger going into the winter. In turn, this agrees with a recent study that clearly demonstrates the correlation between overwintering success and colony strength.

I suggest re-reading 2 that post as I’m going to try and avoid too much repetition here.

Strong colonies

Strong colonies overwinter better and – if you’re interested in that sort of thing – are much more likely to generate a profit for your honey sales.

So how can you ensure strong colonies at the end of the season?

What influences colony strength?

One thing is colony health. A healthy colony is much more likely to be a strong colony.

In the ambitious 600-colony Büchler study in Europe they didn’t do any disease management. The colonies were monitored over ~2.5 years during which time 84% of colonies perished, at least half due to the ravages of Varroa.

Clearly this is not sustainable beekeeping and doesn’t properly reflect standard beekeeping practices.

Study details

The recent Burnham study makes a nice comparison to the Büchler study.

It was conducted in New York State using 40 balanced 3 colonies requeened in late May.

Queens were sourced from California (~4000 km west) or Vermont (~200km east in the neighbouring state, and therefore considered ‘local’) and colonies were assigned queens randomly.

Unlike some previous studies the authors did not evidence the genetic differences between queens.

A local queen

A local queen

However, the queens looked dissimilar and the stocks were sourced from colonies established in California or Vermont for at least 10-15 generations. I think we can be reasonably confident that the queens were sufficiently distinct to be relevant for the tests being conducted.

Colonies were maintained using standard beekeeping practices, Varroa levels were managed using formic acid (MAQS for European readers) and the colony weight and productivity (frames of bees) was quantified, as was the pathogen load.

In contrast to the Büchler study, Burnham and colleagues only followed colonies over one beekeeping summer season. This was not a test of overwintering survival, but mid-season development.

Results

The take-home message is that colonies headed by the ‘local’ Vermont queens did better. The colonies got heavier faster and brood levels built up better.

Bigger, faster, stronger …

It’s notable that colony weight built up before any brood would have emerged from the new queen (upper panel) and that brood level in colonies headed by the local queen recovered much better after formic acid treatment (arrow in lower panel).

Nosema levels

However, Nosema levels were significantly different (above) as were the levels of Israeli Acute Paralysis Virus (IAPV; below).

Virus loads (DWV, BQCV and IAPV)

There were no significant differences in the Varroa loads before or after treatment (not shown), or in the levels of DWV or Black Queen Cell Virus (BQCV).

Taken together – bigger, heavier, stronger colonies and lower pathogen loads (at least of some pathogens) – seems good evidence to support the contention that local bees are beneficial.

The benefits are precisely what you want for good overwintering – strong, healthy colonies.

That’s a slam-dunk then?

Case proven?

No.

IAPV is a virus rarely detected in the UK. It causes persistent and systemic infections in honey bees and can be found in every caste (drones, workers, queens) and at every stage of the life cycle.

As IAPV is detectable in eggs and larvae – neither of which are Varroa-exposed – it is assumed to be vertically transmitted from the queen. IAPV is also found in the ovaries of the queen, which is additional evidence for vertical transmission.

At the first timepoint (12 days post requeening) the levels of IAPV are different between the two colony types, but not significantly so. However, by 40 days (T2) the levels are very different. At this later timepoint all the bees in the colony will be have come from the introduced queen.

The authors explain the differences in IAPV levels in terms of local bees being more resistant to ‘local’ pathogens … in much the same way that Pizarro’s 168 conquistadors, being more resistant to smallpox, defeated the might of the Inca Empire with the help of the virus diseases they inadvertently introduced to Peru.

I suspect there’s another explanation.

Perhaps the Californian queens were IAPV infected from the outset?

If this was the case they could introduce a new and virulent strain of IAPV to the research colonies and – over time – the levels would increase as more and more workers in the colony were derived from the new queen. IAPV is present in ~20% of US colonies so it seems perfectly reasonable to suggest it might have been largely absent from the Vermont queens and the test colonies, but present in the queens introduced from California.

How should they have tested that?

The obvious thing to do would be to characterise the IAPV present in the colony. IAPV shows geographic variation across the USA. If the predominant virus was of Californian origin it would suggest it was brought in with the queen. This is a relatively easy test to conduct … a sort of 23andme to determine bee virus provenance.

Alternatively, though less conclusively, you could do the experiment the other way round … ship Vermont queens to California and compare their performance with colonies headed by Californian queens on their own territory. If the Californian queens again performed less well it undermines the ‘local bees do better’ argument and suggests another explanation should be sought.

Nosema is sexually transmitted but it is not vertically transmitted, so the same arguments cannot be made there. Why the Nosema levels drop so convincingly in colonies headed by the local queens is unclear. Nosema was present at the start of the study and was lost over time in the stronger colonies headed by the local queens.

One possibility of course is that the stronger colonies were better fed – more workers, more foragers, more pollen, more nectar. Improved diet leads to a more active and effective immune system and an increased ability to combat pathogens. Simplistic certainly, but it is known that diet influences pathogen resistance and colony performance.

So what does this paper show?

I suspect it doesn’t directly show what the authors claim (in the title) … that local queens head colonies with lower pathogen levels.

This largely reflects the lack of proper or complete controls. However, it does not mean that local bees are not better.

More than anything I think this paper demonstrates the impact queen quality has on colony performance.

Perhaps the Vermont-sourced queens were just better queens. Local certainly (on a USA scale definition of the word local), but not better because they were local, just better because they were better.

However, if my interpretation of the source of the IAPV is correct i.e. introduced from the Californian queens, I think the paper indirectly demonstrates one of the most compelling reasons why local bees are preferable.

If they’re local – your apiary, your neighbours, someone in your association – there is little chance they will be bringing with them some unwanted baggage in the form of an undetected exotic pathogen.

Or a more virulent strain of one already circulating relatively benignly.

Extensive bee movements, whether of queens, packages or full colonies, risks spreading parasites and pathogens.

There is compelling evidence that hosts and pathogens co-evolve to reduce the pathogenicity of the interaction. Naive hosts are always more susceptible to introduced pathogens, or novel strains of pre-existing pathogens. After all, look what happened to the Peruvian Inca when they met the measles- and smallpox-ridden conquistadors.

So, when thinking about the claims being made by bee importers (or, for that matter, strong advocates of local bee breeding), it’s worth considering all of the factors at play – queen quality per se, genetic adaptation of the queen to the local environment and the potential for the introduction of novel pathogens with introduced non-local stock.

And that’s before you also consider the benefits to your beekeeping of being self-sufficient and not reliant on others to produce your stocks.

I never said it was simple 😉


 

Spotty brood ≠ failing queen

I thought I’d discuss real beekeeping this week, rather than struggle with the high finance of honey sales or grapple with the monetary or health consequences of leaving supers on the hive.

After all, the autumn equinox has been and gone and most of us won’t see bees for several months 🙁

We need a reminder of what we’re missing.

Beekeeping provides lots of sensory pleasures – the smell of propolis on your fingers, the taste of honey when extracting, the sound of a full hive ‘humming’ as it dries stored nectar … and the sight of a frame packed, wall-to-wall, with sealed brood.

Brood frame with a good laying pattern

This is a sight welcomed by all beekeepers.

Nearly every cell within the laid up part of the frame is capped. All must therefore have been laid within ~12 days of each other (because that’s the length of time a worker cell is capped for).

However, the queen usually lays in concentric rings from the middle of the frame. Therefore, if you gently uncap a cell every inch or so from the centre of the frame outwards, you’ll see the oldest brood is in the centre and the most recently capped is at the periphery.

It’s even more reassuring if the age difference between the oldest and the youngest pupae is significantly less than 12 days. Hint … look at the eye development and colouration.

This shows that the queen was sufficiently fecund to lay up the entire frame in just a few days.

What are these lines of empty cells?

But sometimes, particularly on newly drawn comb, you’ll see lines of cells which the queen has studiously avoided laying up.

That'll do nicely

That’ll do nicely …

It’s pretty obvious that these are the supporting wires for the sheet of foundation. Until the frame has been used for a few brood cycles these cells are often avoided.

I don’t know why.

It doesn’t seem to be that the wire is exposed at the closed end of the cell. I suspect that either the workers don’t ‘prepare’ the cell properly for the queen – because they can detect something odd about the cell – or the queen can tell that there’s something awry.

However, after a few brood cycles it’s business as usual and the entire frame is used.

Good laying pattern ...

Good laying pattern …

All of these laid up frames contain a few apparently empty cells. There are perhaps four reasons why these exist:

  • Workers failed to prepare the cell properly for the queen to lay in
  • The queen simply failed to lay an egg in the cell
  • An egg was laid but it failed to hatch
  • The egg hatched but the larvae perished

Actually, there’s a fifth … the cell may have been missed (for whatever reason) but the queen laid in it later and so it now contains a developing larva, yet to be capped.

What are all these empty cells?

But sometimes a brood frame looks very different.

Worker brood 1 is present across the entire frame but there are a very large number of missed cells.

Patchy brood pattern

Patchy brood & QC’s …

Note: Ignore the queen cells on this frame! It was the only one I could find with a poor brood pattern.

This type of patchy or spotty brood pattern is often taken as a sign of a failing queen.

Perhaps she’s poorly mated and many of the eggs are unfertilised (but they should develop into drone brood)?

Maybe she or the brood are diseased, either reducing her fecundity or the survival and development of the larvae?

Sometimes spotty brood is taken as a sign of inbreeding or poor queen mating.

Whatever the cause, colonies producing frames like that shown above are clearly going to be less strong than those towards the top of the page 2.

So, if the queen is failing, it’s time to requeen the colony …

Right?

Perhaps, perhaps not …

Which brings me to an interesting paper published by Marla Spivak and colleagues published in Insects earlier this year 3.

This was a very simple and straightfoward study. There were three objectives, which were to:

  • Determine if brood pattern was a reliable indicator of queen quality
  • Identify colony-level measures associated with poor brood pattern colonies
  • Examine the change in brood pattern after queens were exchanged into a colony with the opposite brood pattern (e.g. move a ‘failing queen’ into a colony with a good brood pattern)

If you are squeamish look away now.

Inevitably, measuring some of the variables relating to queen quality and mating success involve sacrificing the queen, dissecting her and counting ‘stuff’ … like viable sperm in the spermathecae.

Unpleasant, particularly for the queen(s) in question, but a necessary part of the study.

However, in the long run it might save some queens, so it may have been a worthwhile sacrifice … so, on with the story.

Queen-level variables in ‘good’ and ‘poor’ queens

By queen level variables I mean things about the queen that could be measured – and that differ – between queens with a good laying pattern or a poor laying pattern.

Surprisingly, good and poor queens were essentially indistinguishable in terms of sperm counts, sperm viability, body size or weight.

Poor queens i.e. those generating a spotty brood pattern, weren’t small queens, or poorly mated queens. They were also not more likely to have fewer than 3 million sperm in the spermathecae (a threshold for poorly mated queens in earlier studies).

Furthermore, the queens had no statistical differences in pathogen presence or load (i.e. amount), including viruses (DWV, Lake Sinai Virus, IAPV or BQCV), Nosema or trypanosomes (Crithidia). 

Hmmm … puzzling.

Colony-level variables

So if the queens did not differ, perhaps colonies with spotty brood patterns had other characteristics that distinguished them from colonies with good brood patterns?

Spivak and colleagues measured pathogen presence and amount in both the good-brood and poor-brood colonies.

Again, no statistical differences.

So what happens when queens laying poor-brood patterns are put into a good-brood pattern hive?

And vice versa …

Queen exchange studies

This was the most striking part of the study. The scientists exchanged queens between colonies with poor-brood and good-brood and then monitored the change in quality of the brood pattern 4.

Importantly, they monitored brood quality 21 days after queen exchange. I’ll return to this shortly.

Changes in sealed brood pattern after queen exchange

Queen from good-brood colonies showed a slight decrease in brood pattern quality (but not so much that they’d be considered to now generate poor brood patterns).

However, surprisingly, queens from poor-brood colonies exhibited a greater improvement in brood quality (+11.6% ± 9.9% more sealed cells) than the loss observed in the reverse exchange (-8.0% ± 10.9% fewer sealed cells).

These results indicate that the colony environment has a statistically significant impact on the sealed brood pattern.

Admittedly, a 10-20% increase (improvement) in the sealed brood pattern on the last frame photograph (above) might still not qualify as a ‘good brood pattern’ queen, but it would certainly be an improvement.

Matched and mismatched workers

Since exchanged queens were monitored just 21 days after moving them all the workers in the receiving hive were laid – and so genetically related to – the previous queen.

The authors acknowledge this and comment that it would be interesting to extend the period until surveying the hive to see if ‘matched’ workers reverted to the poor brood pattern (assuming that was what the queen originally laid).

This and a host of other questions remain unanswered and will undoubtedly form the basis of future studies.

The authors conclude that “Brood pattern alone was an insufficient proxy of queen quality. In future studies, it is important to define the specific symptoms of queen failure being studied in order to address issues in queen health.”

Notwithstanding the improvements seen in some brood patterns I suspect they would be insufficient to justify not replacing an underperforming queen … when considering the issue as a practical beekeeper i.e. there may be improvements but they were much less than could be achieved by replacing the queen from a known and reliable source.

But it might be worth thinking twice about this …

Insufficient storage space

In closing it’s worth noting that I’ve seen spotty or incomplete brood patterns when there’s a very strong nectar flow on and the colony is short of super storage space.

Under these conditions the bees start to backfill the brood box, taking up cells that the queen would lay in.

Usually this is resolved just by adding another super or two.

If there remains any doubt (about the queen) and you’ve provided more supers you can determine the quality of the laying pattern by putting a new frame of drawn comb into the brood nest.

The queen should lay this up in a day or two if she’s “firing on all cylinders”.

In which case, definitely keep her 🙂