Category Archives: Swarms

Swarm and mite partitioning

Clipped queen swarm

Clipped queen swarm

When a honey bee colony swarms, what proportion of the bees in the colony leave with the queen?

A simple question and one that has been addressed using elegantly simple experiments.

But swarms don’t leave without also taking Varroa mites with them 1.

What proportion of the Varroa mites in the colony leave with the swarm? In both cases partitioning refers to the proportion that remains with the original colony (bees or mites) and the proportion that disappears over the fence (or appears in your bait hive).

Why does this matter?

If you’re interested in honey from your bees the answer to the first question is very relevant. The more bees that leave, the less remain to forage … so you’ll get less honey.

If you collect swarms or use bait hives to attract them, the answer to the second question is particularly relevant as it emphasises the importance of Varroa treatment of newly-hived swarms.

Does size matter?

Colonies swarm when they are strong, which is usually – but doesn’t have to be – when the colony is big. There are a number of factors that influence swarming, but the strength of the colony i.e. lots of bees in the space available, is one of the most important. A strong nucleus colony of only 3 frames will swarm under similar conditions that induce a huge double-brooded hive to swarm; the latter might contain 75,000 bees, the former perhaps only about 7500.

In addition, because the survival of swarms is influenced by their size (see below) we need to be aware that large and small colonies may behave differently. For example, if only 5000 bees formed a ‘viable’ swarm, the 3 frame nuc described above could generate just one, whereas the double-brooded monstrosity could produce a prime swarm and loads of similarly-sized casts 2. Since swarms of all sizes are seen, it suggests a fixed proportion of the bees leave, rather than a fixed amount …

Counting the bees in a swarm

Occupied bait hive

Occupied bait hive …

Counting large numbers of bees is not a trivial task. Of course, counting the bees in a swarm is pretty straightforward … catch the swarm, weigh it and divide by the weight of a ‘single bee’ 3.

But this doesn’t tell you the number of bees in the original hive. You need to know this to determine the proportion of bees that leave with the queen.

Thomas Seeley from Cornell University used an elegant solution 4 to count the size of the original colony before and after swarming. He established several 3-frame narrow observation hives between gridded glass panels. The hive was so narrow that only a single layer of bees could occupy the beespace between the glazing and the comb. By counting bees in about 10% of the grid squares, averaging and multiplying he could accurately determine the total number of bees in the colony … which was about 7600.

He determined the number of bees in the colony early every morning during the swarming season. Immediately after swarming he counted the bees remaining in the hive. By dividing the number of bees present after the swarm left with the number present that morning he could determine the proportion of the adult workers present in the swarm.

And the answer is …

75%

When Seeley’s small colonies swarmed, 75% of the workers departed in the swarm 5. This figure is in good agreement with previous studies conducted by Getz and colleagues 6 using two larger colonies (~30,000 bees in each, 72% of which left with the swarm), and with work from the 1960’s 7 using small and large colonies (73% and 66% respectively).

Swarm partitioning therefore appears to be colony size-independent, with about 75% of the adult workers departing with the queen.

So, if size doesn’t matter, why does size matter?

A small swarm ...

A small swarm …

Juliana Rangel and Thomas Seeley went on to establish swarms of different sizes – small medium and large, containing 5000, 10,000 and 15,000 bees respectively … and a queen. The large swarms developed into fully-established colonies better (drawing more comb, collecting more nectar and rearing more brood). Most significantly, large swarms had a much higher survival rate. Almost 90% of the small or medium swarms failed to overwinter, whereas 75% of the large swarms survived.

Again, there were precedents for this … in the mid-80’s Lee and Wilson had monitored survival of natural swarms and showed that larger swarms were more successful.

So size matters for swarm survival.

This is perhaps not surprising when you consider all the ‘work’ the colony needs to do to survive the winter – draw out a large area of comb, store about 20kg of honey and rear thousands of new workers.

In addition, it turns out that larger swarms are probably better at choosing suitable nest sites to occupy. This is because they have a larger number of scout bees to find the sites faster, thereby improving the decision-making process.

And, of course, size also matters if you want your colonies to spend their time collecting nectar for honey production. When a colony swarms 75% of the workforce leaves and, inevitably, the productivity of the hive is significantly reduced for an extended period.

Mite partitioning … simple maths surely?

The only mites that can leave the colony when it swarms are those that are phoretic i.e. riding around the colony on adult bees. The remainder are safely tucked away in capped cells gorging themselves on pupae.

Poly Varroa tray from Thorne's Everynuc with visible mites.

Gotcha! …

If we assume that all the adult bees are workers 8 it is a simple calculation to work out the proportion of mites in the colony that leave with the swarm … 0.75 * X, where X is the proportion of mites in the colony that are phoretic.

So, if 10% of the total number of mites are phoretic, 7.5% of the total mites would disappear with the swarm. This could explain the small colony size and frequent swarming of Varroa-tolerant feral colonies … every time they swarm, over 90% of the mites are left behind.

But … there’s always a but …

% of mites in capped cells

% of mites in capped cells

The proportion of phoretic mites in a colony is unfortunately not static. It fluctuates with the availability of suitably-aged larvae to infest. It is therefore influenced by the egg laying rate of the queen.

Numbers often quoted for the experimentally-determined proportion of phoretic mites range from 10-50% (or more), a range reflected in a well-established model for the seasonal reproduction of Varroa 9.

Remember that the graph (right) is modelled data. In a real-world situation there will be brood earlier and later in the year. However, in a first attempt at calculating mite partitioning during swarming in May/June the modelled data is close enough to experimentally-determined data to be usable.

Predicted and real mite partitioning numbers

The extreme values from the May/June (the swarming season) predictions in the graph above indicate that phoretic mites proportions range from 15-50% of the total in the colony. A swarm containing 75% of the adult bees in the hive would therefore also leave with somewhere between 11% and 37% of the Varroa from the colony.

The higher of these figures is quoted by Thomas Seeley in his study of the frequently swarming Varroa-tolerant colonies in the Arnot Forest, though this is calculated from his own swarm partitioning studies and data from others, and was not directly measured.

However, Jerzy Wilde and colleagues have conducted one of the few studies that have experimentally measured mite partitioning in natural and artificially-swarmed colonies. Of seven large colonies (~30,000 bees) which swarmed naturally, 25 ± 9% of mites left the colony with the swarm. Using a Taranov board, 36 ± 11% of mites left the colony with the swarm fraction in the artificially-swarmed colonies.

Sublimox vaporiser

Sublimox vaporiser …

A quarter of all the mites in a heavily infested colony is a lot of mites.

Which is why it’s always sensible to treat swarms you catch/attract/buy 10 for mites.

By definition, all the mites in a swarm are phoretic, so they’re easy to kill using miticides – such as those based on oxalic acid (either trickled or sublimated) – that work best on broodless colonies.

Caveats and future considerations

I have a few concerns about the Wilde study. The size of the swarms generated was significantly smaller than usual, containing only ~45% of adult workers. In addition, the initial mite-infestation levels were quite low, implying that the available open brood was unlikely to be rate-limiting in terms of mite reproduction and the phoretic period.

I’ll return to this in a future post but it’s worth remembering that the queen markedly reduces her egg-laying rate as the colony prepares to swarm. This results in fewer 5-day larvae and so decreases the opportunities for phoretic mites to hide themselves in capped cells.

Swarming colonies may actually have elevated phoretic mite levels …


 

Prime numbers and cast offs

This post was prompted by a recent search used to reach this website. The question posed was can a prime swarm be led by virgin queen if [the] old clipped queen dies trying to lead a swarm?”

Swarming is the natural way that honey bee colonies reproduce. The process is triggered by a number of factors – overcrowding and diminishing levels of queen pheromone being two of the most important.

A small swarm

A small swarm …

Both these are, directly or indirectly, measures of how strong the colony is. If the queen has nowhere to lay because the box is wall-to-wall brood or stuffed with nectar, the colony is effectively overcrowded. In contrast, if the colony has ample space but there are so many bees that the queen pheromone is ‘diluted’, the colony will sense this indirect measure of strength and make swarm preparations.

In addition, as queens age they naturally produce less queen pheromone; colonies headed by older queens are therefore more likely to swarm than those headed by first year queens.

Prime swarms

You’ll see two definitions of prime swarms. Some define it as the swarm headed by the mated, laying queen and others use it to mean the first swarm to issue from a hive.

They’re usually one and the same thing.

Developing queen cells in the hive are capped on the 9th day after the egg they contained was laid. If the weather conditions are suitable – typically early afternoon on a warm, sunny day – the mated queen leaves the hive with up to half the workers.

This swarm – headed by the mated queen and often containing perhaps 20 – 30,000 bees – is the prime swarm. It’s the first to leave the hive … but it might not be the last …

Captured swarm in 8 frame poly nuc

Captured swarm in 8 frame poly nuc …

Casts (or cast swarms)

Seven days after the queen cells were sealed the new, virgin queen emerges (or ecloses). For the continued viability of the original colony this queen needs to be mated and return to the colony. She does this on a warm, sunny day a few days after eclosion.

However, there are often several developing queen cells remaining in a hive after a prime swarm disappears over the fence to the howling wilderness.

This is where things get interesting.

All sorts of things can happen at this point. If the colony is strong enough it will throw off one or more casts. These are small swarms, headed by a virgin queen. Small is a relative term. They’re small in comparison to a prime swarm. Once started a colony can continue to throw off smaller and smaller casts. Some are these small in comparison to a mug of tea.

The continued loss of bees means the colony may effectively ‘swarm-out’, reducing in strength until perhaps only 10% of the original colony remains. If this happens any opportunity of a honey harvest is also lost and there’s a chance the colony will not recover sufficiently in time to overwinter successfully.

To complicate matters further, if multiple queens emerge casts can contain more than one queen. Sometimes you’ll open a hive at the same time as multiple queens are emerging. It can be bedlam trying to catch half-a-dozen virgins scuttling around a busy brood box.

Hiving casts

Large casts – perhaps football-sized – are worth catching and dumping into a nuc. Once the queen gets mated they can develop into a worthwhile colony. Ted Hooper describes ‘rescuing’ smaller casts by uniting them over a queen excluder on top of the supers on a strong hive. The bees unite and the queen is prevented from entering the hive by the excluder. I’ve not had to do this. I’ve lost one or two colonies that swarmed out but missed the ever-diminishing casts altogether.

A cast ...

A cast …

The cast swarm above was collected in a skep and allowed to settle for a few hours. When I lifted the skep from the sheet to dump the bees into a nuc there was a single bee corpse remaining … a dead queen. The cast obviously contained at least two queens. On checking the nuc a week later, after a week of almost continuous rain, I found a single skittish queen running around. Her behaviour suggested she hadn’t yet had an opportunity to get out and mate.

A cast in the skep ...

A cast in the skep …

And the answer is … ?

Consider again the original question … can a prime swarm be led by virgin queen if [the] old clipped queen dies trying to lead a swarm?”. The answer isn’t necessarily straightforward.

I think I’d argue that a swarm led by a virgin queen, despite being the first swarm to leave the hive, is not a prime swarm. It’s viability still depends absolutely on the virgin getting mated.

I would consider it as a cast.

Clipped queen ...

Clipped queen …

Clipped queens have one wing trimmed to restrict their flight. This is a well-established method of swarm control. If the colony swarms the queen drops to the ground and the swarm often clusters with her under the hive. Colonies with clipped queens usually swarm a bit later in the development cycle of the new queen(s) in the colony. However, they are only delayed by a day or two.

I’m therefore puzzled why – as suggested in the question – there was both a clipped queen and an emerged virgin in the colony simultaneously. Or perhaps there wasn’t, but the query was whether a subsequent emerging virgin would head the swarm …

I’m afraid the puzzle will remain. The question came from an internet search … unless the person who posed it reads this and responds all we can do is speculate.


Or perhaps to establish themselves in your neighbours soffits. The same neighbour who has always complained about your bees chasing their dog and stinging their children. Reason enough to try and not lose swarms.

‡ I know this was a cast headed by a virgin queen because it came from a vertical split in which the queenless half was left overly strong. The clipped and mated queen was ‘all present and correct’ in the queenright half of the split – I checked. I’m intending to write a bit more about how to prevent casts in the future … once I’m a little better at it than I’ve been this Spring  😥

Scouting for girls

A swarm of bees is a wonderful sight … if it’s arriving in your bait hive. It’s still dramatic, but perhaps slightly less wonderful, if it’s disappearing over the fence from your apiary 😉

Although some will disagree, I think beekeepers have a responsibility to both control swarming of their own stock, and capture – or attract – swarms lost by others. Although perhaps incomprehensible to us, some don’t share our passion for bees. Many are frightened and a large swarm is an intimidating sight for the melissophobic.

A small swarm ...

A small swarm …

Aside from frightening people, if they move into the church tower or an old hollow tree, they’re likely to develop high levels of Varroa and the pathogenic viruses the mite transmits. As a consequence, they can act as a source of disease to bees in local apiaries, until they’re killed off in the winter. Which they almost certainly will be.

I therefore always put out bait hives in late Spring, well ahead of the expected start of the swarming season (which often coincides with the oil seed rape finishing). I’ve described the basics of bait hives previously – a National-sized, bee-smelling box containing one frame of old, dark comb and half a dozen foundationless frames. I often use stacked supers from the, otherwise-awful, Paradise poly hives for this purpose.

Dyb dyb dyb

One of the greats sights of the swarming season is the appearance of the first scout bees at the bait hive. First one or two, then a dozen and, within hours or days, hundreds. They check out the entrance and the inside the bait hive. They fly all around the perimeter. They’re unaggressive and you can get up close to watch them at work. If you listen carefully you can hear them pinging into the sidewalls and floor of the bait hive as they move about inside.

They actually probably measure the volume by a combination of walking around the inner walls and determining the mean free path length – the average length of all straight lines from wall-to-wall in the hive – in short flights. For an interesting and easily readable discussion of the physics behind this I recommend the short paper by Nigel Franks and Anna Dornhaus (PDF) How might individual honeybees measure massive volumes?

In my view, this alone is a good reason to use foundationless frames in a bait hive.

Scouts often arrive early at the bait hive and leave late. Their numbers will fluctuate with weather and temperature – they’ll disappear altogether in the rain, but reappear in force once a shower has passed.

Scouting around

This short video was taken about 9am, two or three days before a large prime swarm occupied the bait hive. The first scout bees I’d seen had been almost two weeks previously. By midday there were hundreds of bees checking the hive.

However, if you look closely, their behaviour is distinctively different from a colony ‘in residence’. They’re much more hesitant in entering the hive and they tend to check the immediate environment much more closely. In contrast, foragers returning to a colony don’t bother doing a couple of laps of the hive … they approach directly and enter with minimal delay.

Seeley’s swarms

The definitive guide to how scout bees choose suitable locations and then ‘persuade’ the swarm to relocate is Honeybee Democracy by Tom Seeley. This is an outstanding book, beautifully written and illustrated.

Swarm of bees

Swarm of bees

Swarming is a two-stage process. The queen and flying bees leave the hive and settle nearby – on a branch, a fence post or (irritatingly) the top of a nearby conifer – creating the classic ‘beard-shaped’ cluster of bees. If you’re lucky with your timing and their location you can knock these into a box and, voila, you have a new colony.

Tom Seeley describes his own studies (based on the equally elegant work of Martin Lindauer in the 1950’s) that determine how scout bees convince the swarm to move from this temporary staging post to a new nesting location – a tree cavity, the church tower or your bait hive. The scout bees use a variation of the classic waggle dance – on the surface of the swarm hanging in the tree – to ‘persuade’ other scouts to check out the location they’ve found. Through repeated cycles of recruitment and reinforcement a consensus is reached and the scouts then lead the swarm to their new home.

That’s the abridged version. Read the book. There are subtleties and anecdotes throughout Honeybee Democracy that mean it’s the sort of book you can go back to time and time again, learning something new each time.

Early scouts

I was puzzled by the swarm that arrived in my bait hive. The first scouts appeared early in the first week of May. I was abroad from the 7th to the 14th and confidently expected the swarm to be waiting for me when I got back. However, it wasn’t until at least another week had elapsed – during which scout bee interest continued unabated – that the swarm arrived.

Honeybee democracy

Honeybee democracy

I went back to Honeybee Democracy and re-read the second chapter (‘Life in a honeybee colony’) and learnt – or was reminded – that there are early scout bees that are able to judge both nest site quality and the state of the colony preparing to swarm. These scouts are at work before the colony swarms. Uniquely these bees are judging both the availability and suitability of new homes and the readiness of the colony to swarm.

They can also tell whether it’s a nice day. The coincidence of these factors – good weather, readiness of the colony to swarm (i.e. sealed queen cells) and potential nest sites – initiate a behavioural change in these scouts that leads to the colony swarming.

Are these scouts the earliest sign of swarm preparation?

What Seeley doesn’t say is just how early in the swarming cycle these scout bees start their initial explorations.

Queens take 16 days to develop from new-laid eggs to eclosion, and just nine days to the sealing of the queen cell. If we assume that the first scouts I saw were from the same hive that subsequently swarmed (and delivered itself to my bait hive) then these scouts were out and about well-before queen cells were even started.

Of course, I have no way of telling whether the first scouts I saw were from the same colony that finally swarmed and arrived. Nevertheless, it’s an interesting thought. Perhaps scout bee interest in a bait hive pre-dates the first definitive swarm preparation signs beekeepers can usually recognise – the appearance of charged queen cells?

Considering the density of beekeepers (by which I mean apiaries 😉 ) in the UK it’s not easy to see how this would be useful … unless you’re the only beekeeper on an isolated island.

However, if you see do scout bee activity at your bait hives it might be worth being more assiduous than usual when checking your own colonies in the neighbourhood.

 


Dyb dyb dyb is an abbreviation for ‘do your best‘. This was part of a cub (not scout) ceremony and was followed by Dob dob dob (‘do our best‘). It was abandoned in the late sixties, but lives on in tricky questions on Qi.

Colophon

Scouting for Boys

Scouting for Boys …

The title of this post is a play on ‘Scouting for Boys‘, the book on Boy Scout training, written and illustrated (originally) by Robert Baden-Powell and published in 1908. The book contains sections on scoutcraft, woodcraft, tracking, camp life, endurance, chivalry, life saving and patriotism. It was the inspiration for the scout movement and Baden-Powell was the founder and first Chief Scout of the Boy Scouts Association (and the founder of the Girl Guides). It is estimated that 4 million copies sold in the UK alone, with global sales in the 20th Century exceeding 100 million.

The book even contains reference to honey bees with the statement that bees form a ‘model community, for they respect their Queen and kill their unemployed’.

The Boy Scouts of America used to offer merit badges in Beefarming (1915-1955) and Beekeeping (from 1955). The Beekeeping merit badge was discontinued in 1995.

Scouting for Girls is an English pop rock band. They have recently announced their 10th Anniversary Tour (Oct/Nov 2017) which means they’re much too new for me to know any of their music 😉

 

Those pesky mites

DWV symptoms

DWV symptoms

If you haven’t yet treated your colonies to reduce Varroa levels before the winter arrives it may well be too late. High Varroa levels are known to result in the transmission of virulent strains of deformed wing virus (DWV). These replicate to very high levels and reduce the lifespan of bees. If this happens to the ‘winter bees’ raised in late summer/early autumn there’s a significant chance that the colony will die during the winter.

Mite levels in most of my colonies have been very low this year. Partly due to thorough Varroa management in the 2015/16 winter (the only thing I can take credit for), partly due to the relative sparsity of beekeepers in Fife, partly due to the late Spring and consequent slow build-up of colonies and partly due to an extended mid-season brood break when requeening. Most colonies yielded only a small number of mites (<50) during and after a 3 x 5 day treatment regime (to be discussed in detail in a later post) by sublimation.

Infested arrivals

The low mite drop definitely wasn’t due to operator error or vaporiser malfunction. At the same time I treated a swarm that had moved into a bait hive in early June …

Out, damn'd mite ...

Out, damn’d mite …

This is ~20% of the Varroa tray. Have a guess at the number of mites in this view only. Click on the image to read the full legend which includes the mite count.

The image above was taken on the 18th of September, a day or two after starting the second round of 3 x 5 day treatments. The colony really was riddled. When a colony swarms 35% of the mites in the colony leave with the swarm (or, in this case, arrives with it). For this reason the swarm was treated for mites shortly after it arrived in June. It did have a reasonably high mite load but subsequently built up very quickly and didn’t experience the mid-season brood break my other colonies benefitted from.

The colony now has an acceptable mite drop (<1 per day). Similar colonies are still rearing brood – I’ve not checked this one, but they are bringing in some pollen from somewhere – so there’s a possibility the majority of the remaining mites are tucked away in sealed cells. I’ll keep a close eye on this colony through the next few weeks and will be treating again midwinter to further reduce the parasite burden.

Treat ’em right

If you are treating this late in the season make sure you use a miticide that is appropriate for the conditions. Apiguard (a thymol-containing treatment) is almost certainly unsuitable unless you’re living in southern France as it needs a temperature of 15°C to be effective. MAQS has a recommended temperature minimum of 10°C which may be achievable.

Hard chemicals such as Apivar and Apistan can be used at lower temperatures but there’s little point in treating with Apistan unless you’re certain all your mites are sensitive. They almost certainly are not as Apistan/Bayvarol resistance is very widespread in the UK mite population. Just because you get an increased mite drop in the presence of Apistan does not mean treatment has been effective. Perhaps all you’ve done is killed the sensitive mites in the population, leaving the remainder untroubled. This is what’s known as a bad idea … both for your bees next season and for your neighbours.


 I’m posting this now due to the large number of searches for, and visits to, pages on use of Apiguard or other Varroa treatments. These are currently running second to ‘fondant‘ in one form or another.

No, not really …

Was it good for you? … No, not really.

I recently posted the weather forecast for the week beginning the 15th of August. I was pleased that the forecast was for near-perfect queen mating conditions – sunny, warm and calm – as I had three colonies which should have contained virgin queens that were due to emerge a few days before.

The forecast was very accurate. Conditions were wonderful. I wasn’t around as I had disappeared to Torridon and Skye for a few days. On checking the colonies at the end of the week after I returned, all three contained queens at least two of which were laying.

Beinn Eighe

Beinn Eighe …

All good then …

Well, not entirely, because mid-afternoon on the previous Wednesday I’d been sent an email from my friend at the apiary that read … “Incredible roaring noise attracted me outside the workshop – a swarm moving west through the garden and into the trees.  All caught on camera”. I didn’t receive the email as I was in the howling wilderness. Not that I could have done much about it.

A very quick inspection of the colony in question on my return confirmed that they’d swarmed. D’oh! I’d obviously missed at least one additional queen cell (mistake #1) on the last inspection and a large cast (the queen must have been a virgin as the original queen had been removed from the colony) had disappeared over the fence … mistake #2. There was a queen present but bee numbers were significantly down. I closed the colony up and disappeared on business for a further three weeks … mistake #3.

The weather had been great the entire week I was away in Torridon. I suspect the colony swarmed on the Monday or Tuesday, that it hung around in a nearby tree until the Wednesday while the scout bees found somewhere more desirable to relocate to, and that my friend had seen it leaving the neighbourhood that afternoon.

Lessons learned

  1. Don’t let the colony decide how many queens should emerge. Instead leave only one known charged (occupied) queen cell to emerge. I’d left an open queen cell on a marked frame, but had not returned a few days later to check that a) it was safely sealed and b) that they hadn’t raised anymore. They had 🙁  Consequently they swarmed when the first queen emerged, leaving one or more additional queens to emerge, fight it out and then head the now much-depleted colony (see 3, below).
  2. Leave a bait hive in or near the apiary, even if the main period of swarming has passed. I’ve been very successful with bait hives over the years, successfully attracting my own and others’ swarms. In this instance the main swarming period was well-passed and I’d packed away my bait hives until next Spring. Wrong. Had I left one near the apiary I may well have managed to attract the swarm and so a) not lost the bees, and b) not potentially inflicted the  bees on someone else. I view bait hives (and queen clipping) as part of being a good neighbour.
  3. Don’t leave a weakened colony late in season. On returning from my three week absence for work I discovered the colony had been robbed out and destroyed. Clearly it had been unable to defend itself from robber bees or wasps and had perished. I should have instead made an executive decision on discovering the colony had swarmed and probably sacrificed the virgin queen and united the weakened colony with a strong colony nearby. In retrospect this was an obvious thing to do … the colony was weak, wasps were beginning to be a problem, there was little or no nectar coming in and the weather was uncertain. As it turned out the weather was good enough for queen mating while I was away. However, the combination of a dearth of nectar, a weakened colony and strong neighbouring colonies meant that robbing was inevitable and – for the colony in question – catastrophic.
Skye ...

Skye …

Had I thought carefully about things in mid-August I may have been able to prevent the inevitable carnage when the colony was robbed out. In my defence I’ve only been around for a day or two over the last month, with extended periods out of the country on business. Nevertheless, this was clearly a case of a lesson (or three) learned the hard way …


† If you’ve not read Tom Seeley’s outstanding Honeybee democracy about how a swarm decides where to relocate to you should.

Same time, next year

About this time last year a swarm arrived in a bait hive in my back garden in Fife. Almost exactly one year later a different bait hive in the same spot was occupied by another swarm … or, possibly, a very good-sized cast.

The bait hive was being investigated by scout bees for a few days but on 6th, which was a very warm day here in Fife, the numbers increased markedly from a couple of dozen to a hundred or more. On my return from work on the following day the swarm was in residence. My neighbour reported seeing a ‘huge swarm arriving’ at about 11am.

Foundationless frames and bait hives

The hive contained a single old, dark brood frame and about five foundationless frames, together with a cotton bud dipped in lemongrass oil. I’ve previously described why I think foundationless frames are so convenient for bait hives – they provide the bees with guides to build new comb without taking up significant space in the box. It’s worth remembering that the scout bees are seeking out a sheltered, south facing, bee-smelling (ideally), empty space of about 40 litres volume i.e. about the same as a single National brood box. Foundationless frames take up little space, but mean that an arriving swarm can start building new comb immediately … and they do.

I posted a photo last week of a swarm from the bee shed that had clustered because the queen was clipped and so unable to fly. I dealt with the swarm within a couple of hours of it settling. Once cleared, the wall of the bee shed was dotted with small crescents of wax as the bees had already started to build new comb. In the bait hive, when checked on the evening of the 8th (less than 48 hours after the bees arrived) they were well on their way to drawing out the first three foundationless frames, with the first of these being half full of nectar, presumably from the dregs available in the nearby OSR fields.

Mite treatment be needed?

Almost certainly … and there’s no better time. When swarms leave a hive they take with them up to 35% of the Varroa population as phoretic mites. A large swarm from a heavily infested hive can therefore introduce an unhealthy dose of virus-riddled mites to your apiary. These will rapidly spread to your other hives. I therefore routinely treat swarms with suitable miticides soon after they arrive, well before any brood is sealed. I don’t look for DWV symptoms or bother searching for signs of phoretic mites, I just treat. Due to work commitments this swarm had to be treated on the third day after arrival, before I was even certain whether the queen was laying or not. Within the first 24 hours after treatment (with sublimated oxalic acid) there were about 40-50 mites on the board, with more falling over the next couple of days. It’s far easier and more effective to treat when there’s no brood present and so give the colony the very best chance of getting well established without a pathogenic virus load.

Finally, after a day of heavy rain, I took advantage of the bees being all ‘at home’, sealed the entrance and relocated them to another apiary to make space for a replacement bait hive on the same spot … on the off chance that swarming here isn’t over yet.

If it is, then there’s always the same time, next year.


Same time, next year was a 1978 romantic comedy starring Alan Alda and Ellen Burstyn about a couple, married to others, who meet by chance, develop an “instant rapport” or at least “really hit it off” (one of the quotes from the film) and then meet again, year after year, both gradually changing, ageing and dealing with life’s crises.

Divide and conquer

Tom Seeley (of Honeybee Democracy fame) published an interesting paper in the journal PLoS One recently on “How honey bee colonies survive in the wild: testing the importance of small nests and swarming” – the paper is available as a PDF following this link (Loftus et al., 2016 PLoS One 11:e0150362).

Size matters

Using his normal elegant methodology Seeley formally tested the observed reduction in colony size and increased swarminess (is that a word?) of – feral or otherwise – colonies ‘selected’ to survive without Varroa treatment by simply abandoning them. The hypothesis – based on previous studies and an understanding of the biology of Varroa – was that colonies ‘forced’ to swarm by being confined in small hives would inevitably:

  • lose significant amount of Varroa through the act of swarming
  • experience a brood break so delaying Varroa replication while requeening
  • consequently survive better than large colonies in which pathogen levels inexorably increased to a level that would destroy the colony

Testing the hypothesis

He tested this by establishing adjacent apiaries (so they have the same microclimate) with either small (~40 litres … about the same as a National brood box) or large (~170 litre) volume hives and installing nucs in each which contained similar levels of brood, bees and Varroa. No Varroa control was performed. Those in the small hives were not managed to prevent swarming whereas those in the large hives were – with the caveat that the colony was kept together (i.e. queen cells were destroyed, brood frames were spread and ample supers were added). The study lasted two years, with regular monitoring of the colony strength, Varroa infestation level etc.

High levels of DWV

High levels of DWV …

To cut a long (but nevertheless interesting and worth reading) story short … the results support the original hypothesis. During the first year of the study the colonies developed in a broadly similar manner from transfer of the nuc to the large or small hive in June until the season’s end. However, by the following May the large hived colonies were almost twice as populous as those in the small boxes. This continued until August, with the average adult bee population in the small and large hives being ~10,000 and ~30,000 respectively. During this second season 10/12 small hives swarmed, whereas only 2/12 of the large hived colonies swarmed. In the latter mite levels dramatically increased to >6/100 adult bees (i.e. riddled with the little b’stards – my opinion, Seeley is too polite to comment). For comparison, the picture above has ~100 bees in it, with one visible Varroa, but has lots of overt deformed wing virus disease. In contrast, the small hived colonies – with the exception on one sampling point discussed later – had three to five times fewer mites than seen in the large hived colonies. By the second winter 10/12 large hived colonies had perished whereas only 4/12 small hived colonies had succumbed, and one of these was to a drone laying queen, not disease. Perhaps most tellingly, 7/12 large hived colonies had signs of overt deformed wing virus (DWV) disease – pathetic, tottering newly emerged workers with stunted abdomens and shrivelled wings – whereas none of those in small hives showed obvious disease.

Great … Varroa-tolerant colonies … where can I get some?

A small swarm

A small swarm

So, what does this mean in terms of practical beekeeping? Firstly, it suggests that it is possible to keep honey bee colonies without treatment or intervention. But – and it’s a biggy – the colonies will be too small to collect meaningful amounts of honey and will spend their time and energy swarming instead. 10,000 adult bees does not a colony make, as Aristotle didn’t say. Or at least not a colony that’s of any practical use for the honey-gathering goal of beekeeping. Ted Hooper (“Bees and honey“), and many others, have made the point that one big colony will gather more nectar than two smaller colonies. Secondly, these small colonies will chuck out loads of Varroa-riddled swarms. Seeley has previously demonstrated that swarming colonies lose ~35% of their Varroa load with the bees that leave the colony. Although this clearly benefits the original colony it potentially distributes Varroa-laden bees (and the smorgasbord of viral pathogens that are the real problem) to whichever local beekeeper finally hives them. This explains the need for prompt Varroa treatment of any swarms you might acquire.

On a more positive note this study clearly shows the benefit of a brood break in terms of restricting the replication and amplification of Varroa. Presumably this is primarily due to the 3+ week window with no sealed brood for Varroa to infest, though it may also mean that broodless colonies might get rid of Varroa at a faster rate with no brood present to distract them. It would be interesting to have compared mite levels immediately after swarming and in the subsequent weeks until the new queen starts laying. Randy Oliver has also discussed the benefits of a brood break during empirical development (and computer modelling) of his beekeeping methods for Varroa control. In his forthright manner he explains “Take home message: early splitting knocks the snot out of mite levels“.

Why discuss this if they’re no use for beekeeping … ?

There was one exception to the generally low mite levels in the small hived colonies and that was late summer in the second year when they all exhibited a large spike in Varroa numbers. This was attributed to robbing-out a collapsing, and soon to die-off completely, large hived colony in the adjacent apiary. The two study apiaries were in the same field. This emphasises the points made in earlier posts about the impact of drifting and robbing and the, at least theoretical benefits of, coordinated Varroa control. Of course, ~2 mites per 100 adult bees in the small hived colonies is not really a low number at all. Assuming a colony size of 10,000 adults with 80% of the mites in capped cells the total Varroa load would be ~1000 in the colony, the threshold level above which the NBU consider treatment is required to avoid loss of the colony.

Divide and conquer

The Varroa loss achieved by swarming, coupled with the break in brood rearing, help the colony conquer – or more correctly tolerate – Varroa levels that otherwise rapidly increase and destroy a colony. However, this is neither a practical or acceptable solution to the Varroa problem. ‘Beekeepers’ (an oxymoron surely?) that allow their colonies to swarm indiscriminately both reduce their chance of getting a good honey crop and impose their – potentially Varroa-ridden – swarms on the neighbourhood. This is irresponsible. In contrast, beekeepers who carefully monitor their colonies and use an effective combination of integrated pest management – for example, including an enforced brood break during the ‘June gap’, or a vertical split, perhaps – benefit from large, healthy, honey-laden§ colonies which overwinter better.


§ at least in the good years 😉

Late arrivals

Stacked boxes

Stacked boxes …

I’m moving house in a couple of weeks and so stacked unused ‘bee equipment’ in a pile on the patio for packing. Some of the supers contained drawn comb from previous years, some of the broods were empty and some contained prepared foundationless frames. I thought I’d taken care to align everything reasonably well to ensure they were ‘beetight‘ when I finished up late on Thursday evening. However, I’d misaligned a chest high stack in the middle and unknowingly left a finger-width crack which allowed some scouts to decide it was a desirable site. Sometime mid-morning on Friday – when I was in the office – a good sized swarm arrived. I hadn’t noticed any scouts checking out the location. I originally thought it was robbers cleaning out honey from the supers, but a quick peek under the roof (there was no crownboard on the stack) showed they were busy drawing comb. Going by the numbers of bees present it looked like a prime swarm, but you can’t be sure unless you find the laying queen.

They couldn’t have chosen a much less suitable (for me … it obviously suited them 😉 ) stack to set up home in. The bottom three boxes were empty broods, topped with three supers, two of which were part filled with drawn drone foundation. Inevitably the spacing of the frames in the supers was all over the place. Removing the roof gently showed they were already building brace comb, attached to the roof and/or the frames. The bees were accessing the stack somewhere in the middle, on the face against the wall. What a mess.

Rearranging the hive

Rearranging the hive …

I fired up the smoker and got kitted up. It was relatively easy to split the stack and put a temporary floor below the supers (with the entrance facing the wall) and put a crownboard in place. The colony were agitated but not aggressive. There were far too many bees to try and find the queen. It was a hot day and there was a whirling maelstrom of bees. I was concerned that the queen – if she was mated – would start laying up the drawn drone foundation in the supers. By evening the stack was quietly humming away, with all the bees inside, so I moved them a few feet away to a purpose-built stand (the ubiquitous milk crate) … swarms can be relocated within 24-48 hours of arrival during which time the “3 foot, 3 mile rule” can be safely ignored.

Blackberry

Blackberry …

Early on Saturday morning I put a new floor and brood box filled with frames on the stand, then added a clearer board and put the two supers full of bees on top. The hope was that many of the foragers would move down into the brood box, leaving the queen and attendants above the clearer. I peeked through the perspex crownboard on Sunday morning and the number of bees in the supers was much reduced. A quick inspection located a very dark unmarked laying queen in the supers. One wing was pretty tatty so she might be quite old. To my surprise the bees had re-engineered a big patch of the drawn drone comb in the super frame to make worker-sized cells and that was the area she’d laid up. In addition, they’d also piled in a surprisingly large amount of nectar – presumably from blackberry which is just developing well at the moment. I rearranged the brood box, moving the queen on the laid-up super frame into the bottom box, then shook the remaining bees off the super frames and closed the colony up.

Ready for OA treatment ...

Ready for OA treatment …

Finally, late on Sunday evening I treated the colony by oxalic acid vaporisation. With no sealed brood in the hive it’s a perfect time to reduce the phoretic mite numbers by at least 95%. Since I have no idea about the provenance of the swarm – other than being sure its not from one of my colonies, all of which have marked and/or clipped queens – this gives at least some peace of mind that a range of unpleasant diseases aren’t being introduced to the apiary with the bees, or the mites they’re carrying. I’ll check the Varroa drop over the next few days and monitor the quality of sealed brood before deciding what to do with them. However, I suspect they’ll either be requeened or given away to an association member still wanting bees, or quite possibly both as I unite other colonies in preparation for moving.

The faint sniffing is my hay fever … I’m not testing the OA vapour. The latter is a significant lung irritant and I’m wearing safety goggles and a mask for personal protection. I’ll post something separately on the Sublimox vaporiser later in the season.

Note Unlike an earlier swarm only about ten mites dropped after OA vaporisation within the first 24 hours which is very reassuring. Some claim that only healthy colonies swarm and, although there is some truth in this (i.e. only strong healthy colonies build up sufficiently to swarm), it doesn’t mean the swarm won’t have a high phoretic mite load. Since, by definition, swarms are brood-free it’s an ideal time to treat them.

Swarm care and treatment

As I left my out apiary last Friday evening I gently tapped a bait hive buried in the grass and nettles and was met with a healthy buzz and a few inquisitive worker bees … it had obviously been occupied by a swarm in the last day or two, despite me not having seen any scout bees investigating it.

Super poly bait hive

Super poly bait hive …

I checked the hive on Sunday and found a small swarm covering about 3-4 frames with a dark, unmarked laying queen. She’s definitely not from my colonies as all mine in that apiary are marked and accounted for. At the back of the hive was an unoccupied wasps nest, beautifully constructed from paper-thin chewed wood pulp. This is the second bait hive with squatters this year.

Waspkeeping

Waspkeeping …

Although there’s a reasonable flow from something at the moment (early blackberry?) I gave them a couple of pints of syrup on Monday and Wednesday evening to help them draw comb on the foundationless frames that fill the box. It’s not advisable to feed syrup immediately in case the honey stores brought with the swarm are contaminated with foul broods – by delaying feeding (or not feeding at all) the bees use their stores to draw wax. I also treated the colony – which has no sealed brood yet of course – with oxalic acid vapour from a Sublimox vaporiser (shown below being used early in the season on a full colony) bought a few months ago from Icko Apiculture.

Sublimox vaporiser

Sublimox vaporiser …

The phoretic mites on a swarm carry an unpleasant payload of viruses including deformed wing virus. It’s therefore good practice to keep the swarm in isolation until it’s known to be healthy, and to treat appropriately for mites as soon as possible. I also treated the churchyard swarm caught last Thursday with OA vapour despite not yet being sure whether the queen is mated or not – if she is then it’s best to treat before the colony have sealed brood, if she isn’t then OA vaporisation is sufficiently ‘gentle’ that I don’t expect the treatment to interrupt her from getting out and mated in the current good weather. By treating with OA vapour late in the evening I wouldn’t interrupt a mating flight and could be pretty sure that most of the bees – and therefore most of the mites – were ‘at home’.

Poly Varroa tray from Thorne's Everynuc with visible mites.

Gotcha! …

It’s good practice to keep records on where swarms were found, hived and how they were subsequently treated.

 

Churchyard swarm

Quiet churchyard

Quiet churchyard

While away on ‘bee health’ business for the day in York I received a call around midday that there was a swarm settling in a small tree in a local churchyard. The combination of the words “small tree” and “within arms reach” is always reassuring, so I promised to have a look when I got back. Inevitably I was delayed and it was nearly 9pm by the time I turned up in the churchyard. I fully expected it to have been collected by another beekeeper, or to have disappeared to a bait hive or even the church tower … but it hadn’t. The swarm was quite small (I suspect it may be a cast) and tightly clustered – exactly as described, in a small tree easily reachable without steps. Excellent.

As the final peals of the bells died out I dropped the swarm into an eight frame poly nuc box, gently lowered a full complement of foundationless frames on top, replaced the perspex cover sheet and roof and waited while the few stragglers entered the box. It was lovely sitting in the gathering gloom listening to the fanning bees at the entrance – indicating the queen was in the box – as the evening ebbed away. It was too dark for any photographs unfortunately. Shortly after 10pm the nuc box was installed in my garden on a levelled stand – to allow the bees to draw the foundationless frames out vertically – and they were busy making orientation flights when I checked at 6am the following day.

Although the bees looked perfectly healthy I’ll keep them away from my main apiaries until I see some brood and can check them thoroughly. In the meantime, and before they have sealed brood, I’ll treat them with oxalic acid vapour to minimise the phoretic mite numbers. To help them draw out new foundation I’ll give them a few pints of thin syrup (I’m still using up some old fondant left over from last winter) if the current nectar flow dries up – the rape is gone and the blackberry is just starting, but my other colonies are bringing something in. Finally, I’ll keep a close eye on their temper and general behaviour and, if unacceptable, will either requeen them or unite them with another colony.