Category Archives: Behaviour

Diutinus bees

Diutinus is Latin for long-lasting.

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

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

Winter is coming …

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

Diutinus does not mean winter

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

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

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

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

Segueing into winter bee production 

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

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

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

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

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

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

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

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

Winter bees are like nurse bees but different

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

Other than being long-lived what are their characteristics?

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

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

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

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

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

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

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

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

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

No single trigger

In temperate regions what distinguishes winter from autumn or spring? 

Temperatures are lower in winter.

Daylength (photoperiod) is shorter in winter.

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

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

And forage availability will, inevitably, influence brood rearing.

Tricky.

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

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

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

Brood, brood pheromones and ethyl oleate

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

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

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

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

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

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

But it’s not only brood that produces pheromones.

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

A picture is worth a thousand words

All of the above is quite complicated.

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

Proposed model for regulation of production of winter bees.

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

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

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

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

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

Is that all?

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

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

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

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

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

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

Don’t forget …

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

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

Early autumn colonies

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

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

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

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

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


 

More gentle beekeeping

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

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

… but nevertheless quite successful 🙂

23,000 iced buns

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

Which means a couple of days of very heavy lifting.

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

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

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

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

As convenience foods go, it’s very convenient.

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

Beekeeper’s back

There’s a bittersweet irony to the honey harvest.

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

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

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

Which appears not to have happened 🙁

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

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

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

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

Quick fix clearer board – hive side

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

Clearing supers

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

Lots of bees

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

More lifting 🙁

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

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

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

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

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

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

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

Lugless …

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

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

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

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

Storm Francis

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

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

Very wet.

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

It was wetter and more miserable than this photo suggests …

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

Cold, clammy and heavy … a wet bee suit

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

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

Hogwash.

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

Stings

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

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

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

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

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

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

Of course, I spoke too soon …

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

Bang, bang, bang, bang, bang … BANG!

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

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

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

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

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

More bittersweet season endings

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

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

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

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

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


 

Orientation flights

Part of the reason for the success of honey bees is the division of labour between workers of different ages. Young workers (hive bees) clean the cells, nurse larvae and look after the queen. Older workers are foragers, collecting pollen and nectar (and water) from across the landscape.

To be successful, foragers need to know where to look and how to return.

The ‘where to look’ is partly accounted for by the well-known waggle dance 1.

In this post I’m going to discuss the second component of successful foraging – the homing ability of foragers.

More specifically, I’m going to discuss how the bee first learns about the location of the hive. 

Orientation flights

Bees do not instinctively know where the hive (or the tree they are nesting in for a wild colony) is located. They have to learn this before embarking on foraging trips to collect nectar or pollen.

This learning takes the form of one (or usually several – as we shall see) orientation flights. These enable the bee to memorise the precise location of the hive with relation to geographic landmarks. On subsequent foraging flights the bees use these landmarks to return to the hive.

Orientation flight have a characteristic appearance …

… and are very nicely described in the introduction to a paper by Capaldi and Dyer 2:

An orientation flight at the nest entrance begins as a departing bee turns and hovers back and forth, turning in short arcs, apparently looking at the hive entrance. Then, the bee increases the size of the arcs until, after a few seconds, she flies in circles while ascending to heights of 5–10 metres above the ground. This spiraling flight takes the bee out of sight of human observers. She returns a few minutes later, always without nectar or pollen.

Which I couldn’t have written any better, so have reproduced verbatim.

There are a number of features of the orientation flight that are immediately obvious from this description (which all beekeepers will recognize). These include:

  • A ‘local’ component, in the immediate vicinity of the hive
  • Wider ranging flight at a greater altitude and a longer distance
  • Direct observation does not allow the location, duration or track of these distant flights to be monitored
  • The bee returning from the orientation flight does not bring pollen or nectar with her

Do orientation flights allow orientation?

How do we know that these flights enable the bee to learn where the hive is located?

Early studies conducted by Becker (1958) showed that bees captured after a single orientation flight and then re-released up to 700 metres away from the hive could find their way ‘home’. In contrast, bees that had not gone on an orientation flight before were, by definition, disoriented and did not return to the hive.

However, the percentage that returned after undertaking a single orientation flight was related to the distance of the release point, and was never more than ~60% (at 200 metres). 

In contrast, reorienting older foragers (for example, as happens after moving a hive to a new location) were much better (~90%) at returning to the hive after a single reorientation flight. 

Capaldi and Dyer extended these early studies by Becker to investigate the impact of the visibility of local landmarks on orientation and reorientation, and also measured the speed with which bees returned after being displaced.

Landmarks

These studies showed that a single orientation flight allowed bees to identify the landmarks in the immediate vicinity (100 – 200 m) of the hive. When released from more distant locations, returning flights were faster and more successful (i.e. fewer lost bees) when the bees had sight of the landmarks in the vicinity of the hive.

The hive itself was effectively invisible except at very short ranges. This makes sense for a tree-nesting animal. One tree looks much the same as another 3, but if you learn that the nest is in the tree between the very tall conifer and the long straight hedgerow – two features visible from hundreds of metres distant – then orientation is straightforward.

This suggests that apiaries located near distinctive landscape features may be preferable in terms of increased returning forager rates.

“Distinctive” as far as an orienting worker bee is concerned, which may not be the same as distinctive to the beekeeper of course 😉

Reorienting bees (compared to first flight bees) took longer to explore the environment and were better at returning. Either these bees learn differently (a distinct possibility) or their prior experience in the wider landscape gives them an advantage when the hive is relocated.

Where do you go to my lovely?

The early studies by Becker and those by Dyer and colleagues defined many of the parameters that characterise orientation flights. What they did not do is show where the bees actually go during the orientation flights?

Do they just zoom around randomly?

Do they fly ever-increasing spirals?

Perhaps they perform some sort of grid search, exploring individual landscape features carefully for future reference?

Recent developments with harmonic radar have allowed tracking of individual bees during orientation flights over hundreds of metres. These have provided further insights into the process.

Because harmonic radar is also relevant to other studies of honey bee flight – for example, the impact of neonicotinoids on foraging ability – I’ll digress slightly from orientation flights to describe the technology.

Harmonic radar

Harmonic radar has revolutionised tracking studies of insects in much the same way as GPS tags have provided unique insights into bird migration (or, for that matter, shark migration).

The radar system has two components. The insect is tagged with a tiny antenna attached to a Schottky diode (together termed the transponder). The transmitter/detector is a ground-based scanner that transmits the radar signal. This is used as the energy source by the diode which re-emits a harmonic of the original signal which can then be detected.

Tagged bumble bee (left) and harmonic radar detector (right)

The transponder weighs less than a normal pollen load, though presumably there is some wind resistance from the antenna. In studies of bees with and without transponders fitted the orientation flights were of a similar duration, suggesting any wind resistance didn’t appreciably impact the flying ability of the bee.

Orientation (a-c) and foraging (d) flights monitored by harmonic radar.

 

Orientation flights 4 were taken by bees between 3 and 14 days post-emergence, with the mean onset of foraging being 14 days post-emergence.

Bees took between 1 and 18 orientation flights, though there wasn’t a direct relationship between the number of flights and the age of the bee, suggesting they may learn at different rates.

Initial orientation flights were generally in the immediate vicinity of the hive. Older workers – pre-foraging – ventured further afield. More recent studies have addressed this in greater detail (see below).

Orientation flights were distinctly different from foraging flights. The former were slower and less direct. The ground speed of orienting bees was ~3.6 m/s in contrast to foragers who flew at ~5.6 m/s and, as shown in D above, foraging flights were very much ‘there and back’ straight lines.

Venturing forth …

A more recent study 5 has used harmonic radar to investigate multiple orientation flights by individual bees, effectively analysing how the bee explores the landscape as it ages towards a forager.

This was a remarkable study. It involved addition and subsequent removal of the transponder from 115 individual bees during 184 orientation flights. When the orienting bee returned they recaptured it, removed the transponder and allowed it to reenter the hive. When it reappeared for another orientation flight they reattached the transponder.

Anyone complaining about their inability to mark queens 6 should do this as a training exercise 😉

The scientists also recorded several foraging flights of a smaller number of the same bees, to allow comparison with their behaviour during orientation flights.

Orientation and foraging flights of five individual bees.

Flights were defined as short or long range, but long range orientation flights were still significantly shorter than foraging flights.

  • Short range flights were made in poor weather and familiarised the bees with the immediate vicinity of the hive.
  • Consecutive long range flights reduced in duration as the bees learnt about the immediate hive vicinity i.e. the long range flights included some local exploring at first as well.
  • Orientation flights explored different areas of the landscape, rather than focusing on one sector.
  • Subsequent foraging flights involved areas that the bees may have never visited during orientation flights.
  • Some very long duration foraging flights may involve a degree of exploration, though it’s not clear whether this is truly orientation, or actual scouting activity.

Not all bees performed short and long range flights though early long range lights did involve local exploration as well. 

Ground clues and conclusions

The final part of this study investigated the influence of visual landscape features on orientation flights. This deserves a post in its own right as the techniques are quite involved.

Essentially they generated heat maps of the flights overlaid onto the geography. Using this approach they determined that some features visible from the air e.g. borders between grassland and a track, influenced the direction of flight and hence the orientation flights. 

There are additional studies of the influence of visible landmarks on bee flight which I’ll return to at some point in the future.

Again, like the comment made above about visible landmarks, it suggests to me that apiaries situated near such distinctive features may aid orientation and subsequent homing flights by honey bees.

When you next stand by your hive entrance on a warm, sunny afternoon and watch young workers flying to and fro across the entrance before spiralling up and away out of sight, you’ll know that it is an essential component of their training to be effective foragers.

They don’t forage for long – perhaps three weeks at most – but they are very effective, partly because they know where to return to.


Notes

Where do you go to my lovely? was the title of a rather syrupy (my blog, my opinion! … Apologies if it’s a favourite of yours 😉 ) song by Peter Sarstedt in 1969. It’s notable for some quite clever rhyming lyrics and a particularly dodgy mustache he sports in the YouTube video. (I’m just linking it, rather than embedding just because of the mustache).

It has nothing to do with bees.

 

The gentle art of beekeeping

High summer.

The swarm season had been and gone. The June gap was over. Grafts made at the peak of the swarm season had developed into lovely big fat queen cells and been distributed around nucleus colonies for mating.

That was almost six weeks ago.

From eclosion to laying takes a minimum of about 8 days. The weather had been almost perfect for queen mating, so I was hopeful they’d got out promptly, done ‘the business’, and returned to start laying.

That would have been about a month ago.

Good queens

I’d spent a long morning in the apiary checking the nucs and the colonies they were destined for. In the former I was looking for evidence that the queen was mated and laying well. That meant looking for nice even frames of sealed worker brood, with some – the first day or two of often patchy egg laying – now emerging.

Brood frame with a good laying pattern

It was warming up. More significantly, it was getting distinctly close and muggy. I knew that thunderstorms were predicted late in the afternoon, but by late morning it already had that oppressive ‘heavy’ feel to the air. Almost as though there wasn’t quite enough oxygen in it.

Never mind the weather, the queens were looking good. 90% of them were mated and laying well.

Just one no-show. She’d emerged from the cell, but there was no sign of her in the nuc, and precious few bees left either.

Queenless nucs often haemorrhage workers to nearby queenright colonies (or nucs), leaving a pathetic remainder that may develop laying workers. There’s no point in trying to save a colony like that.

Actually, it’s not even a colony … it’s a box with a few hundred abandoned and rapidly ageing workers. Adding resources to it – a new queen or a frame of eggs and young larvae – is almost certainly a waste of resources. They’d better serve the colonies they were already in. The remaining workers were probably over a month old and only had another week or two before they would be lost, ‘missing in action’, and fail to return from a foraging flight.

If you keep livestock, you’ll have dead stock.

These weren’t dead stock, but they were on their last legs, er, wings. I shook the workers out in front of a row of strong colonies and removed the nuc box so there was nowhere for them to return. The workers wouldn’t help the other colonies much, but it was a better fate than simply allowing them to dwindle.

Spare queens

Most of the nucs were going to be used to requeen production colonies. A couple had been promised to beginners and would be ready in another week or so.

Midseason is a good time to get a nuc to start beekeeping. The weather – the predicted (and seemingly increasingly imminent) afternoon thunder notwithstanding – is more dependable, and much warmer. The inevitably protracted inspections by a tyro won’t chill the brood and nucs are almost always better tempered than full colonies. In addition, the new beekeeper has the pleasure of watching the nuc build up to a full colony and preparing it for winter. This is a valuable learning experience.

Late season bramble

Late season bramble

It’s too late to get a honey crop from these midseason nucs (usually, there may be exceptional years) but that’s probably also good training for the new beekeeper. An understanding that beekeeping requires a degree of patience may be a tough lesson to learn but it’s an easier one than discovering that an overcrowded nuc purchased in April, swarms in May, gets really ratty in June and needs a new queen at the beginning of July.

But, after uniting the nucs to requeen the production hives it turned out that I had one queen spare.

Which was fortunate as I’d been asked by a friend for an old leftover queen to help them improve the behaviour of their only colony. Rather than give them one of the ageing queens she could have the spare one from this year.

A queen has a remarkable influence over the behaviour and performance of the colony. Good quality queens head calm, strong colonies that are a pleasure to work with. But it’s not all good genes. You can sometimes detect the influence of a good new queen in a poor colony well before any of the brood she has laid emerges. I assume this is due to pheromones (and with bees, if it’s not genetics or pheromones I’m not sure what else could explain it – ley lines, phase of the moon, 5G masts nearby?).

Go west, young(er) man

My friend lived about 45 minutes away. I found the queen in the nuc, popped her into a marking cage and placed her safely in light shade at the back of the apiary while I rearranged the nuc for uniting over a strong queenright colony.

Handheld queen marking cage

Handheld queen marking cage

A few minutes later I’d recovered the queen, clipped her and marked her with a white Posca pen. I alternate blue and white (and sometimes yellow if neither of those work or can be found) and rely on my notes to remind me of her age should I need to know it. I’m colourblind and cannot see – or at least distinguish – red and green, either from each other or from lots of other colours in the hive.

I transferred the marked queen into a JzBz queen cage and capped the exit tube. Of all the huge variety of queen introduction cages that are available these are my favourite. They’re also the only ones I was given a bucket of … something that had a big part to play in influencing my choice 🙂

JzBz queen cages

JzBz queen cages

I put the caged queen in the breast pocket of my beesuit, extinguished the smoker and tidied up the apiary. It was warm, dark and humid in the pocket – for an hour or so she would be fine.

Actually, it was getting increasingly humid and the heaviness in the air was, if anything, getting more oppressive.

What I’d really like now would be a couple of large mugs of tea … I’d inspected a dozen large colonies and nearly the same number of nucs. The colonies that needed requeening had been united with the nucs (having found and removed the ageing queens) and I’d neatly stacked up all the empty nuc boxes in the shed. Finally, I’d retuned all the supers, some reassuringly heavy, and left everything ready for the next inspection in a fortnight or so 1.

That’s a lot of lifting, carrying, bending, squinting, prising, turning, rearranging and then gently replacing the crownboard and the roof.

Not really hard work, but enough.

Actually, quite enough … I’d really like that cuppa.

Was that thunder? Way off to the west … a sound so faint I might have imagined it. There were towering cumulus clouds building along the horizon.

Cloud

Threatening

Time to get a move on.

With the car packed I lock the apiary gate and set off.

West.

Leaving the flat agricultural land I climbed gently into low rolling hills. The land became more wooded, restricting my view of the thunderheads building, now strongly, in the direction I was heading. The sun was now intermittently hidden between the wispy clouds ahead of the storm front.

Could you do me a favour?

The bad weather was still a long way off. I’d have ample time to drop the queen off, slurp down a cuppa and be back home before any rain arrived. If my friend was sensible she’d just leave the new queen hanging in her cage in a super. The workers would feed her until the weather was a little more conducive to opening the hive and finding the old queen.

I pull into the driveway and my friend comes out to meet me. We share beekeeping chat about the weather, forage, the now-passed swarm season, the possibility of getting a nuc for next season 2.

“Could you perhaps requeen the colony? I’m really bad at finding the queen and they’ve been a bit bolshy 3 recently. I’ll put the kettle on while you’re doing it.”

I did a quick mental calculation … weighing up the positives (kettle on) and the negatives (bolshy, the distant – but approaching – thunder) and was surprised to find that my yearning for a cuppa tipped the balance enough for me to agree to do it.

I returned to the car for my smoker and some queen candy which I used to plug the neck of the JzBz cage. At the same time I also found a small piece of wire to hang the cage between the frames from.

“They’re in the back garden on the bench by the gate to the orchard.”

I look through the kitchen window across the unkempt lawn (was the mower broken?). Sure enough, there was a double brooded National hive topped with two supers on a garden bench about 30 metres away.

“I’ll stay here if you don’t mind … they gave me a bit of a fright when I last checked them.”

Sure. No problem. I’ve done this a hundred times. White, no sugar and, yes, I’d love a cookie as well.

Be properly prepared

I stepped into the back garden and fired up the smoker. It was still warm from being used for my own bees and the mix of cardboard, woodshavings and dried grass quickly started smouldering nicely. A couple of bees had come to investigate but had just done a few laps of my head and disappeared.

But they returned as I walked across the lawn.

And they brought reinforcements.

By the time I was half way across the lawn I’d been pinged a couple of times. Not stung, but the sort of glancing blow that shows intent.

A shot across the bows, if you like.

I didn’t like.

I pulled the veil over my head and zipped it up quickly, before rummaging through my pockets to find a pair of gloves. Mismatched gloved. A yellow Marigold for my left hand and a thin long-cuff blue nitrile for my right. It’s an odd look 4 but an effective combination. The Marigold is easy to get on and off, and provides ample protection.

Nitriles ...

Nitriles …

The nitrile is a bit of a nightmare to get on when it’s still damp inside. Another couple of bees dive bomb my veil, one clinging on and making that higher pitched whining sound they make when they’re trying to get through. I brushed her off with the Marigold, turned the nitrile inside out, blew into it to inflate the fingers, and finally got it on.

Why two different gloves? Two reasons. I’d lost the other Marigold and because nitriles are thin enough to easily pick a queen up with, and that’s what I’d been doing most of the morning.

And hoped to do again shortly when I found the old queen in the agitated colony.

Opening hostilities

I approached the hive. It was a strong colony. Very strong. It was tipped back slightly on the bench and didn’t look all that stable 5. I gave them a couple of puffs of smoke at the entrance and prised the supers up and off, placing them propped against the leg of the bench.

I was faintly aware of the smell of bananas and the, still distant, sound of thunder. It probably wasn’t getting any closer, but it certainly wasn’t disappearing either.

The thunder that is.

The smell of bananas was new … it’s the alarm pheromone.

Actually, it’s one of the alarm pheromones. Importantly, it’s the one released from the Koschevnikov gland at the base of the sting. This meant that one or two bees had already pressed home a full attack and stung me. Felt nowt. Presumably they’d hit a fold in the beesuit or the cuff of the Marigold.

Or my adrenaline levels were sufficiently elevated to suppress my pain response.

I was increasingly aware of the number of really unpleasant bees that were in the hive.

And, more to the point, coming out of the hive.

But I was most aware that I was only wearing a single thickness beesuit in the presence of 50,000 sociopaths with a thunderstorm approaching. Under the suit I had a thin short sleeved shirt and a pair of shorts.

It might be raining in half an hour … this could get ugly.

It was late July, it was a hot day, my bees are calm. I wasn’t dressed appropriately for these psychos.

I felt I needed chain mail … and an umbrella.

Time for a rethink

I gave the hive a couple of larger puffs from the smoker and retreated back to the car, ducking under and through – twice – some dense overhanging shrubs to deter and deflect the bees attempting to hasten my retreat.

Ideally I’d have put a fleece on under the beesuit. That makes you more or less impervious to stings.

Did I mention it was a warm day in July? No fleece 🙁

However, I did have a beekeeping jacket in the car. This is what I wear for most of my beekeeping (unless I’m wearing shorts). I removed the jacket hood and put it on over the beesuit, remembering to transfer the queen to the outer jacket pocket. I also found another nitrile glove and put it on to be double gloved.

“The queen’s not marked”, my friend shouted to me as I walked back across the garden, “Sorry!”

Now you tell me …

I See You Baby

I See You Baby

I returned to the hive. To reduce the immediate concentration of bees, I split the two brood boxes off the floor, placing each several metres away on separate garden chairs. I balanced the supers on the original floor to allow returning foragers and the increasing maelstrom of flying bees to have somewhere to return if needed.

And then I found the unmarked queen.

As simple as that.

Amazingly, it was on the first pass through the second brood box.

Each box was dealt with in the same way. I gently split the propolis sealing the frames together – first down one side of the box, then the other. I removed the outer frame, inspected it carefully and placed it on the ground leaning against the chair leg. With space to work I then methodically went through every frame, calmly but quickly.

I didn’t expect to find her so easily. I wasn’t sure I’d be able to find her at all.

It helped that she was huge and pale. It helped that she was calmly ambling around on the frame, clearly confident in the knowledge that there were 50,000 acolytes willing to lay down their lives to protect her.

Her confidence was misplaced 🙁

Veiled threat

And then a bee got inside the veil.

This happens now and then. I suspect they sneak through the gap where the zips meet at the front or the back. There are little Velcro patches to hold everything together, but it was an old suit 6 and the Velcro was a bit worn.

There are few things more disconcerting that 50,000 psychos encouraging a Ninja worker that’s managed to break through your defences and is just in your peripheral vision. Or worse, in your hair. With a calm colony you can retreat and deal with the interloper. You have to take the veil off. Sometimes you have to take the suit off.

Removing the veil would have been unwise. Perhaps suicidal. I retreated a few yards and dealt with the bee. It was never going to end well for one of us 🙁

Reassemble in the reverse order

Returning to the original bench, I removed the supers that were now festooned with thousands of bees, balancing them against the leg again. I found a pencil-thick twig and used it under one corner of the floor to stop everything wobbling. Both brood boxes were returned, trying to avoid crushing too many bees at the interface. A combination of a well aimed puff or two of smoke, brushing the bees away with the back of my hand and placing the box down at an angle and then rotating it into position reduced what can otherwise cause carnage.

I hung the new queen in her cage between the top bars of the central frames in the upper box, returned the queen excluder and the supers and closed the hive up.

It took 15 minutes to avoid and evade the followers before I could remove the beesuit safely. I’d been stung several times but none had penetrated more than the suit.

I finally got my cup of tea.

Confidence

This was several years ago. I took a few risks towards the end with the queen introduction but got away with it. The colony released the queen, accepted her and a month or so later were calm and well behaved.

I was lucky to find the queen so quickly in such a strong colony. I didn’t have to resort to some of the tricks sometimes needed to find elusive queens.

Ideally I’d have left the queen cage sealed to see if they were aggressive to her, only removing the cap once I was sure they’d accept her. This can take a day or two, but you need to check them.

There was no way I was going back into the hive and my friend definitely wasn’t.

The rain and thunder never arrived … like many summer storms it was all bluster but eventually dissipated as the day cooled.

This was the worst colony I’ve ever handled as a beekeeper. At least for out and out, close quarter, bare knuckle aggression. By any measure I’d have said they were unusable for beekeeping. I’ve had colonies with followers chase me 300 metres up the meadow, though the hive itself wasn’t too hot 7. This colony was an order of magnitude worse, though the followers were less persistent.

I suspect that aggression (or, more correctly, defensiveness) and following have different genetic determinants in honey bees.

Lessons

  • Knowing when to retreat is important. Smoking them gently before I returned to the car for a jacket helped mask the alarm pheromone in the hive and gave me both time to think and renewed confidence that I was now better protected.
  • Confidence is very important when dealing with an unpleasant hive. It allows you to be unhurried and gentle, when your instincts are screaming ‘get a move on, they’re going postal’.
  • Confidence comes with experience and with belief in the protective clothing you use. It doesn’t need to be stingproof, but it does need to protect the soft bits (my forearms, ankles and face react very badly when stung).
  • Indeed, it might be better if it’s not completely stingproof. It’s important to be aware of the reactions of the colony, which is why I prefer nitrile gloves to Marigolds, and why I never use gauntlets.
  • Many colonies are defensive in poor weather or with approaching thunderstorms. If I’d known just how defensive this colony were I’d have planned the day differently.
  • The unstable ‘hive stand’ would have agitated the bees in windy weather or during inspections.

Bad bees

It turned out the colony had been purchased, sight unseen, as a nuc the year before. By the end of the season it had become unmanageable. The supers had been on since the previous summer and the colony hadn’t been treated for mites.

They appeared healthy, but their behaviour was negatively influencing their management (and the upkeep of the garden). Beekeeping isn’t fun if you’re frightened of the bees. You find excuses to not open the hive, or not mow the lawn.

The story ended well. The new queen settled well and the bees became a pleasure to work with. My friend regained her confidence and is happy to requeen her own colonies now.

She has even started using proper hive stands rather than the garden bench … which you can now use for relaxing on with a mug of tea and a cookie.

While watching the bees 🙂


 

Barcoding bees

Every jar of honey I prepare carries a square 20mm label that identifies the apiary, batch, bucket and the date on which is was jarred. The customer can scan it to find out about local honey … and hopefully order some more.

The label looks a bit like this:

Scan me!

This is a QR code.

You’ll find QR codes on many packaged goods in the supermarket, on bus stop adverts, on … well, just about anything these days.  QR codes were first used in 1994 and are now ubiquitous.

QR is an abbreviation of quick response.

It’s a machine-readable two-dimensional barcode that is used to provide information about the thing it’s attached to.

QR codes contain positional and informational content. In the image above the three corners containing large squares allow the orientation to be unambiguously determined.

Within the mass of other, much smaller, black and white squares are several alignment points, an indication of the encoding 1 and the ‘information payload’. 

Large QR codes can contain more information and more error correction (so they can be read if damaged 2 ). Conversely, small QR codes contain reduced amounts of information and less error correction, but can still be used to uniquely identify individual things in a machine-readable manner.

A barcoded bee and barcode diagram.

And those ‘things’ include bees.

I am not a number 3

I had intended to write a post on how pathogens alter honey bee behaviour. This has been known about in general terms for some time, but only at a rather crude or generic level. 

To understand behavioural changes in more detail you need to do two things:

  • observe bees in a ‘natural setting’ (or at least as natural as can be achieved in the laboratory)
  • record hundreds or thousands of interactions between bees to be able to discriminate between normal and abnormal behaviour. 

And that isn’t easy because they tend to all look rather similar.

Lots of bees

How many of the bees above are engaging in trophallaxis?

Does the number increase or decrease over the next five minutes? What about the next hour?

And is it the same bees now and in an hour?

And what is trophallaxis anyway? 

I’ll address the last point after describing the technology that enables these questions to be answered.

And, since it’s the same technology that has been used to monitor the behavioural changes induced by pathogens, I’ll have to return to that topic in a week or two. 

Gene Robinson and colleagues from the University of Illinois at Urbana–Champaign have developed a system for barcoding bees to enable their unique identification 4.

Not just a few bees … not just a couple of dozen bees … every bee in the colony.

Though, admittedly, the colonies are rather small 😉

Each barcode carries a unique number, readable by computer, that can be tracked in real time.

So, unlike Patrick McGoohan, these bees are a number.

bCode

The scientists designed a derivative of the QR code that could be printed small enough to be superglued to the thorax of a worker bee. They termed these mini-QR-like codes bCodes 5. The information content of a bCode was limited by its size and the reference points it had to carry that allowed the orientation of the bee to be determined.

In total the bCode could carry 27 bits of data. Eleven bits (each essentially on or off, indicated by a black or white square) encoded the identification number, allowing up to 2048 bees to be uniquely numbered. The remaining 16 bits were the error-correction parity bits that had to be present to ensure the number could be accurately decoded.

If you’re thinking ahead you’ll realise that the maximum number of bees they could therefore simultaneously study was 2048. That’s about 1/25th of a very strong colony at the peak of the season, or the number of bees covering both sides of a two-thirds full frame of sealed brood.

It’s enough bees to start a one frame nucleus hive, which will behave like a mini-colony 6 and, in due course, expand to be a much larger colony.

And if you’re thinking a long way ahead you’ll realise the every barcode must be affixed to each bee in the same orientation. How otherwise would you determine whether the bees were head to head or abdomen to abdomen?

Labelling bees

This is the easy bit.

Each bCode was 2.1mm square and weighed 0.6mg i.e. ~0.7% of the weight of a worker bee. Honey bees can ‘carry’ a lot more than that. When they gorge themselves before swarming they ingest ~35mg of honey. 

The bCode therefore should not be an encumbrance to the bee (and they confirmed this in an exhaustive series of control studies).

A single frame of sealed brood was incubated and the bees labelled within a few hours of emergence. Typically, two batches of ~700 bees each were labelled from a single frame for a single experiment.

Each bee was anaesthetised by chilling on ice, the bCode glued in place (remember … in the same orientation on every bee) and the bee allowed to recover.

Labelling a single bee took 1-2 minutes.

Labelling 1400 bees takes several people a long time.

I said it was easy.

I didn’t say it was interesting.

Smile for the camera

I’ve not yet discussed the goal of the study that needed barcoded bees. It’s not really important while I’m focusing on the technology. Suffice to say the scientists wanted to observe bees under near natural conditions.

Which means a free-flying colony, on a frame of comb … in the dark.

Free-flying because caged bees do not behave normally.

On a frame of comb because they were interested in the interactions between bees under conditions in which they would normally interact.

And in the dark because that’s what it’s like inside a beehive (and it’s one of the features that scout bees favour when selecting a site for a swarm).

Camera and hive setup.

The scientists used an observation hive with a difference. It had an entrance to allow the bees to fly and forage freely and it contained a single sided, single frame. In front of the frame was a sheet of glass separated by 8mm from the comb. This prevented the bees from clambering over each other, which would have obscured the bCodes 7. Behind the frame was an 850nm infrared lamp to increase contrast, and the front was illuminated by several additional infrared lamps.

Bees cannot see light in the infrared range, so they were effectively in the dark.

The camera used (an Allied Vision Prosilica GX6600 … not your typical point and shoot) recorded ~29MP images every second. A typical experiment would involve the collection of about a million images occupying 4-6 terabytes of hard drive space 8.

The recorded images were processed to determine the temporal location of every bee with a visible (and readable) bCode. This was a computationally interesting challenge and involved discarding some data – e.g. barcodes that moved faster than a bee can walk or barcodes that fell to the bottom of the hive and remained motionless for days (i.e. dead bees). About 6% of the data was discarded during this post-processing analysis.

Trophallaxis

Which finally gets us to the point where we can discuss trophallaxis. 

Honey bees and other social insects engage it trophallaxis.

It involves two insects touching each other with their antennae while orally transferring liquid food. It occurs more frequently than would be required for just feeding and it has been implicated in communication and disease transmission

bCoded bees and trophallaxis

So, if you are interested in trophallaxis, how do you determine which bees are engaging in it, and which are just facing each other head to head?

In the image above the two bees in the center horizontally of the insert 9 are engaged in trophallaxis. The others are not, even those immediately adjacent to the central pair.

Image processing to detect trophallaxis – head detection.

This required yet more image processing. The image was screened for bees that were close enough together and aligned correctly. An additional set of custom computer-vision algorithms then determined the shape, size, position and orientation of the bees’ heads. To be defined as trophallaxis the heads had to be connected by thin shapes representing the antennae or proboscis.

And when I say the image … I mean all million or so images.

Bursty behaviour

And after all that the authors weren’t really interested in trophallaxis at all.

What they were really interested in was the characteristics of interactions in social networks, and the consequences of those interactions.

This is getting us into network theory which is defined as “Well out of my depth”

Transmission of things in a network depends upon interactions between the individuals in the network.

Think about pheromones, or honey, or email … or Covid-19.

It’s only when two individuals interact that these can be transmitted between the individuals. And the interaction of individuals is often characterised by intermittency and unpredictable timing. 

Those in the know – and I repeat, I’m not one of them – call this burstiness. 

If you model the spread of ‘stuff’ (information, food, disease) through a bursty human communication network it is slower than expected.

Is this an inherent characteristic of bursty networks?

Are there real bursty networks that can be analysed.

By analysing trophallaxis Gene Robinson and colleagues showed that honey bee communication networks were also bursty (i.e. displayed intermittent and unpredictable interactions), closely resembling those seen in humans.

However, since they had identified every trophallaxis interaction over several days they could follow the spread of ‘stuff’ through the interacting network.

By simply overlaying the real records of millions of interactions over several days of an entire functional community with an event transmitted during trophallaxis they could investigate this spread..  

For example, “infect” (in silico) bee 874 in the initial second and follow the spread of the “infection” from bee to bee through the real network of known interactions.

In doing this they showed that in a real bursty network, interactions between honey bees spread ‘stuff’ about 50% faster than in randomised reference networks. 

Why isn’t entirely clear (certainly to me 10, and seemingly to the authors as well). One obvious possibility is that the topology of the network i.e. the contacts within it, are not random. Another is that the temporal features of a bursty network influence real transmission events. 

Scientists involved in network theory will have to work this out, but at least they have a tractable model to test things on …

… and at a time when some remain in lockdown, when others think it’s all a hoax, when social distancing is 2m 11, when some are wearing masks and when prior infection may not provide protective immunity anyway, you’ll appreciate that ‘how stuff spreads’ through a network is actually rather important.

Stay safe


 

If it quacks like a duck …

Quack

… it might be a trapped virgin queen.

I discussed the audio monitoring of colonies and swarm prediction last week. Whilst interesting, I remain unconvinced that it is going to be a useful way to predict swarming. 

And, more importantly, that replacing the manual aspects of hive inspections is desirable. I’m sure it will appeal to hands off beekeepers, though I’m not sure that’s what beekeeping is about.

However there was a second component to what was a long and convoluted publication 1 which I found much more interesting.

Listening in

If you remember, the researchers fitted hives with sensitive accelerometers and recorded the sounds within the hive for two years. Of about 25 colonies monitored, half swarmed during this period, generating 11 prime swarms and 19 casts.

In addition to the background sounds of the hive, with changes in frequency and volume depending upon activity, some colonies produced a series of very un-bee-like toots and quacks.

Have a listen …

The audio starts with tooting, the quacking starts around 8-9s, and there’s overlapping tooting and quacking from near the 21s mark.

Queen communication

I’ve previously introduced the concept of pheromone-based communication within the hive. For example, the mated queen produces the queen mandibular and queen footprint pheromones, the concentrations of which influence the preparation and development of new queen cells.

Tooting and quacking is another form of queen communication, this time by virgin queens in the colony.

It’s not unusual to hear some of these sounds during normal hive inspections, but only during the swarming season and only when the colony is in the process of requeening.

If you rear queens, and in my experience particularly if you use mini-mating nucs, you will regularly hear “queen piping” – another term for the tooting sound – a day or so after placing a mature charged queen cell into the small colony.

But we’re getting ahead of ourselves. 

How does the queen make these sounds?

Queen piping or tooting

Queen tooting has been observed. The queen presses her thorax tight down against the comb and vibrates her strong thoracic wing muscles. Her wings remain closed. The comb acts as a sounding board, amplifying the sound in the hive (and presumably transmitting the vibrations through the comb as well).

This doesn’t happen just anywhere … the virgin queen is usually near the cell she has recently emerged from. 

And this swarm cell is usually on the periphery of a frame.

This is because the laying queen only rarely ventures to the edges of frames, so the concentration of her footprint pheromone is lower in this area, eventually resulting in queen cells being produced there

In their study, accelerometers embedded in the periphery of comb were able to detect much stronger tooting and quacking signals, supporting the conclusions of Grooters (1987) 2 who had first published studies on the location of piping queens.

Queen tooting and quacking

Queen piping is usually recorded at around 400 Hz and consists of one or more 1 second long pulses, followed by a number of much shorter pulses. In previous studies the frequency of tooting had been shown to be age-related. It starts at ~350 Hz and rises in frequency to around 500 Hz as the virgin queen matures over several days.

Compare the image above with the audio file linked further up the post. The tooting is followed by an extended period of quacking, and then both sounds occur at the same time.

Going quackers

The duck-like quacking is presumably also made by queens vibrating their flight muscles while pressed up against the comb.

I say ‘presumably’ as I don’t think it has been observed, as opposed to heard.

The reason for this is straightforward, the queens that are quacking are still within the closed queen cell.

Quacking is a lower frequency sound (is this because of the confines of the queen cell, the way the sound is produced, or the ‘maturity’ of the queen’s musculature?) but has also been shown to increase in frequency – from ~200 Hz to ~350 Hz – the longer the queen remains within the cell.

Afterswarms = casts

Before discussing the timing of tooting and quacking we need to quickly revisit the process of swarming. I’ve covered some of this before when discussing the practicalities of swarm control, so will be brief.

  1. Having “decided” to swarm the colony produces swarm cells. Usually several.
  2. Weather permitting, the prime swarm headed by the original laying queen leaves the hive, on or around the day that the first of the maturing queen cells is capped.
  3. Seven days after the cell was capped the first of the newly developed virgin queens emerges. 
  4. If the colony is strong, this virgin also swarms (a cast swarm). Some texts, including the publication being discussed, call these afterswarms.
  5. Over the following hours or days, successively smaller cast swarms may leave the hive, each headed by a newly emerged virgin queen.

Not all colonies produce multiple cast swarms, but initially strong colonies often do.

From a beekeeping point of view this is bad news™. It can leave the remnants of the original colony too weak to survive and potentially litters the neighbourhood with grapefruit, orange and satsuma-sized cast swarms. 

Irritating 🙁

Whether it’s good for the bees depends upon the likelihood of casts surviving. The very fact that evolution has generated this behaviour suggests it can be beneficial. I might return to this point at the end of the post.

Tooting timing

The Grooters paper referred to earlier is probably the definitive study of queen tooting or piping. The recent Ramsey publication appears to largely confirm the earlier results 3, but has some additional insights on colony disturbance during inspections 4.

Here is the acoustic trace of an undisturbed colony producing a prime swarm and two casts.

Timing of tooting and quaking in a swarming colony

I’ve added some visible labels to the image above indicating the occurrence of tooting and quacking in an undisturbed naturally swarming colony.

  • The prime swarm exited the hive on the afternoon of the 13th. No tooting had been recorded before that date.
  • On the 17th tooting starts and increases in frequency over the next two days.
  • Quacking starts 6 hours after the tooting starts.
  • The first cast swarm (afterswarm) exits the hive on the 19th and is followed by a three hour break in tooting.
  • Tooting and quacking then continue until the second cast swarm on the afternoon of the 21st.

So, in summary, tooting starts after the prime swarm leaves and stops temporarily when the first cast leaves the hive. Quacking starts after the tooting starts and then continues until the last swarm leaves the hive.

Why all the tooting and quacking?

The timing of queen tooting is consistent with it being made by a virgin queen that has emerged from the cell. The cessation of tooting upon swarming (the first afterswarm) suggests that the virgin left with the swarm. The restarting of tooting a few hours later suggests a new virgin queen has been released from another cell and is announcing her presence to the colony.

In previous studies, Grooters had shown that replaying the tooting sound to mature virgin queens actively chewing their way out of a queen cell delayed their emergence by several hours. This delay allowed the attendant workers to reseal the cell and obstruct her emergence for several days.

These timings and the behaviour(s) they are associated with suggest they are a colony-level communication strategy to reduce competition between queens. 

The newly emerged virgin queen toots (pipes) to inform the workers that there is ‘free’ queen in the colony. The workers respond by holding back emergence of other mature queens. 

If all (or several) of the virgin queens emerged and ran around the hive simultaneously they would effectively be ‘competing’ for the hive resources needed for successful swarming i.e. the workers. 

By controlling and coordinating a succession of queen emergence, a strong colony has the opportunity to generate one, two or more cast swarms whilst sufficient workers remain in the hive. It presumably helps ensure the casts are of a sufficient size to give them the best chance of survival.

At what point does this succession stop or break down? One possibility is that this happens when there are insufficient workers to prevent additional virgin queens from emerging.

Unanswered questions

Why do mature virgin queens within the cell quack? It is clearly a response to tooting, rather than being standard behaviour of a soon-to-emerge queen. 

Hear! Hear the pipes are calling, Loudly and proudly calling (from Scotland the Brave)

Is the quacking to attract workers to help reseal the cell?

I suspect not. At least, I suspect there is a more pressing need to attract the workers. After all, wouldn’t it be easier for the queen to simply stop chewing her way out for a few hours? 

Isn’t there a risk that a quacking cell-bound queen might attract the virgin queen running around ‘up top’ who might attempt to slaughter her captive half-sister? 

Possibly, so perhaps the workers that are attracted to the quacking cell also protect the cell, preventing the loose virgin queen from damaging the yet-to-emerge queens.

This would make sense … if the virgin leaves with a cast, the workers that will remain must be sure that there will be a queen available to head the colony

And finally, back to the tooting. I also wonder if this has additional roles in colony communication. For example, what other responses does it induce in the workers? 

Does the increasing frequency of tooting inform the workers that the virgin is maturing and that they should ready themselves for swarming? Perhaps tooting above a certain frequency induces workers to gorge themselves with honey to ensure the swarm has sufficient stores?

In support of this last suggestion, studies conducted almost half a century ago by Simpson and Greenwood 5 concluded that a 650 Hz artificial piping sound induced swarming in colonies containing a single mobile (i.e. free) virgin queen.

Casts

The apparently self-destructive swarming where a colony generates a series of smaller and smaller casts seems to be a daft choice from an evolutionary point of view.

Several studies, in particular from Thomas Seeley, have shown that swarming is a risky business for a colony … and that the majority of the risk is borne by the swarm, not the parental colony. 

87% of swarmed colonies will rear a new queen and successfully overwinter, but only 25% of swarms survive. And the latter figure must only get smaller as the size of the swarms decrease. 

One possibility is that under entirely natural conditions a colony will not undergo this type of self-destructive swarming. Perhaps it is a consequence of the strength of colonies beekeepers favour for good nectar collection or pollination?

Alternatively, perhaps it reflects the way we manage our colonies. Ramsey and colleagues also record tooting and quacking from colonies disturbed during hive inspections. In at least one of these their interpretation was that there were multiple queens ‘free’ in the hive simultaneously, presumably because workers had failed to restrict the emergence of at least one virgin queen.

So, perhaps hive inspections that (inadvertently) result in the release of multiple virgin queens are the colonies that subsequently slice’n’dice themselves to oblivion by producing lots of casts.

I can only remember one colony of mine doing this … and it started days after the previous inspection, but that doesn’t mean the disturbance I created during the inspection wasn’t the cause.

I’d be interested to know of your experience or thoughts.


Colophon

The title of this post is derived from the Duck Test:

If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck.

This probably dates back to the end of the 19th Century. It’s a form of abductive 6 reasoning or logical inference. It starts with an observation or set of observations and then seeks to find the simplest and most likely conclusion from those observations. In comparison to deductive reasoning, logical inference does not lead to a logically certain conclusion. 

Inevitably, Monty Python stretched the logical inference a little too far in the Witch Logic scene from Monty Python and the Holy Grail:

What do you do with witches? Burn them! And what do you burn apart from witches? Wood! So, why do witches burn? ‘cos they’re made of wood? So; how do we tell if she is made of wood? Build a bridge out of ‘er! Ah, but can you not also make bridges out of stone? Oh yeah. Does wood sink in water? No, it floats! It floats! Throw her into the pond! What also floats in water? Bread! Apples! Very small rocks? Cider! Gra-Gravy! Cherries! Mud! Churches? Churches! Lead, Lead. A Duck! Exactly. So, logically… If she weighs the same as a duck, she’s made of wood… and therefore… a witch!

Swarm prevention

Swarm prevention and control are distinct phases in the management of colonies during the next few weeks of the beekeeping season 1.

Not all beekeepers practice them and not all colonies need them.

But most should and will … respectively 😉

Swarm prevention involves strategies to delay or stop the colony from initiating events that lead to swarming.

Swarm control strategies are more direct interventions that are used to prevent the loss of a swarm.

Why do colonies swarm?

Without swarming there would be no honey bees.

Swarming is honey bee colony reproduction. Without management (e.g. splitting colonies) colony numbers would remain static. And, since bees have only been managed for a few thousand years, they must have been successfully reproducing – by swarming – for millions of years before then.

So one of the major drivers of swarming is the innate need to reproduce.

Bees also swarm if their current environment is unable to accommodate further colony expansion. Therefore, another driver of swarming is overcrowding.

And, of course, there is some overlap in these two drivers of swarming.

You can therefore expect that strong, healthy, populous colonies will probably try to swarm on an annual basis.

The mechanics of swarming

When a colony swarms about 75% of the worker bees – of all age groups – leave with the queen. They set up a temporary bivouac near the original hive and subsequently relocate to a new nest site identified by the scout bees.

The original colony is left with all the brood (eggs, larvae and sealed brood), a significantly-depleted adult bee workforce and almost 2 all of the honey stores.

What they lack is a queen.

But what the swarm also leaves behind, amongst the brood, is one – or more often several – newly developing queens. These occupy specially enlarged cells that are located vertically on the edges or face of the comb.

Queen cells ...

Queen cells …

Queen cells look distinctive and their initial appearance – before the swarm leaves – is a clear indication that the time for swarm prevention has gone and swarm control is now urgently needed 3.

This is one of the reasons why regular colony inspections are essential, particularly during mid/late Spring and early summer which is the time of the season when swarming is most likely.

Colony fate and the risks of swarming

But back to the recently swarmed colony. In a few days the new queen(s) emerges. If there’s more than one they usually fight it out to leave just one. She goes on one or more mating flights and a few days later starts laying eggs.

This colony should survive and thrive. They have time to build up strength (and collect more stores) before the end of the season. Under natural conditions 87% of swarmed colonies overwinter successfully 4.

Alternatively, the swarmed colony may swarm again (and again), each with a virgin queen and each further depleting the worker population. Colonies can swarm themselves to destruction like this.

Swarms headed by virgin queens are termed casts. I’m not sure what determines whether a swarmed colony also produces one or more casts. Colony strength is a determinant, but clearly not the only one as some casts contain little more than a cup full of bees.

Under natural conditions swarming is a very risky business. Swarm survival is less than 25% 5 – many will not collect sufficient stores to overwinter – and the survival of casts will be even lower because of their size and the risks associated with queen mating.

But ‘our’ bees don’t live under natural conditions

For beekeeping the ‘risks’ associated with swarming are somewhat different.

When a colony swarms you lose the majority of the workforce. Therefore honey production will be significantly reduced. You’re unlikely to get a surplus from the swarmed colony.

Of course, honey might not interest you but propolis and wax production are also reduced, as is the strength of the colony to provide efficient ecosystem services (pollination).

Secondly, despite swarms being one of the most captivating sights in beekeeping, not everyone appreciates them. Non-beekeepers may be scared and – extraordinary as it may seem – resent the swarm establishing a new nest in the eaves of their house.

Incoming! from The Apiarist on Vimeo.

Inevitably some beekeepers will claim they’ve never met anyone scared of bees, or swarms are always welcomed in the gardens that abut their apiary.

Unfortunately, that does not alter the reality that – to many – swarms are a nuisance, a potential threat and (to a small number of people 6 ) a very real danger.

Therefore, as beekeepers, we have a responsibility to practice both swarm prevention and control. This prevents our hobby/obsession irritating other people and means we have more bees to make delicious honey for family, friends and customers.

Overcrowding

I’ve already defined the event that separates swarm prevention from swarm control. It is the appearance of queen cells during the weekly colony inspection.

Swarm prevention involves managing the colony to delay the appearance of queen cells. Once queen cells are produced, swarm control is required 7

I’ve also defined the two major drivers of swarming – overcrowding and the need to reproduce 8.

How does a colony determine that it is overcrowded? As beekeepers, how can we monitor and prevent overcrowding?

As a colony expands during the spring the queen lays concentric rings of eggs from the centre of the brood nest. Imagine this initially as a kiwi fruit-sized ball, then an orange, then a grapefruit, until it is the size of a large football.

Brood frame

Perhaps a slightly squashed football, but you get the general idea.

Running out of storage space

It takes bees to make bees. The initial brood reared helps feed subsequent larvae and keeps the maturing brood warm.

As the season develops more sources of nectar and pollen become available. These are collected in increasing amounts by the expanding numbers of foragers.

This all needs to be stored somewhere.

One possibility is that the stores are loaded into the cells recently vacated by emerging workers within the brood nest. This is often termed “backfilling”. Sometimes you find a frame in which the central concentric rings of brood have emerged and, before the queen has had a chance to re-lay the frame with new eggs, workers have backfilled the cells with nectar (or, less frequently, pollen).

But, at the same time as the space available for the queen to lay is reducing, the colony population is increasing. Very fast. There are larger numbers of unemployed young bees. Unemployed because there are reduced amounts of brood to rear because the queen is running out of space.

Pheromones

And the increased number of workers means that the pheromones produced by the queen, in particular the queen mandibular pheromone, are effectively diluted. Studies by Mark Winston and colleagues 9 investigated the relationship between queen mandibular pheromone (an inhibitor of queen cell production) and colony congestion. In it he concluded that overcrowding inhibits the transmission of this pheromone, so favouring queen cell production.

Play cup or queen cell?

Play cup or are they planning their escape …?

The distribution of other pheromones is also reduced in overcrowded colonies. Lensky and Slabezki 10 showed that the queen rarely visited the bottom edges of comb in overcrowded colonies. Consequently, the levels of queen footprint pheromone was reduced. This pheromone is an inhibitor of queen cup production, the very earliest stages of queen cell development.

So, overcrowded colonies start to prepare queen cells … and swarm control is needed.

Make space

If the colony is overcrowded then you have to provide more space for colony expansion.

Just piling supers on top may not be sufficient, though it may temporarily ease congestion and partially help. Leaving a colony with no supers during a strong nectar flow is a surefire way to fill the brood box with nectar and trigger swarm preparation.

If the colony is backfilling the brood nest with nectar then the addition of supers is likely to encourage them to move the stores up, providing more space for the queen.

It will additionally have the beneficial effect of moving some bees ‘up’, to store and process the nectar, again reducing congestion in the brood nest.

However, you probably also need to encourage the bees to expand the brood nest by providing frames for them to draw out as comb. Essentially you’re spreading the brood nest by inserting one or two empty frames within it.

Expanding or spreading the brood nest

I routinely do this by removing the outer frames, which often contain stores, and adding new foundationless frames on one or both sides of the centre of the brood nest. Usually I would place these about three to four frames apart 11.

Effectively I’m providing the bees with the space to draw more comb and, in due course, for the queen to lay more eggs.

And all this keeps the workers gainfully employed and so helps alleviate overcrowding.

But what do you do if the box is full of full brood frames?

Brood frame with a good laying pattern

You provide another brood box.

Don’t just dump another brood box on top and expect the bees to immediately move up. It’s a big empty space. Ideally provide some drawn comb and move a frame or two up with emerging bees and the queen. She will rapidly start to lay up the vacated cells and the adjacent frames. Push the original frames together and add new empty frames to fill the box.

You are expanding the brood nest … vertically.

My colonies rarely need this as they are the less prolific, darker bees which tend to perform better overall in Scotland. However, some strains of bees readily fill two stacked brood boxes every season.

It’s worth emphasising again that these swarm prevention interventions are of little or no use for swarm control. If there are queen cells already present adding a frame or two of foundation will have no effect at all.

Young queens

Young queens produce more pheromones than ageing queens. Therefore, all other things being equal, the inhibitory effects of queen mandibular and footprint pheromones will be stronger in a colony headed by a young queen.

This is why colonies are less likely to swarm in their first full season 12.

You can routinely replace queens by purchasing new ones, by rearing your own, or through colony manipulation during swarm control e.g. by reuniting a vertical split.

Of these, I’d strongly recommend one of the last two approaches. It’s more interesting, it’s a whole lot more satisfying and it is a lot easier than many beekeepers realise.

Locally bred queen ...

Locally bred queen …

You have the additional advantage that the queens produced in your own apiary will – by definition – be local and there is good evidence that local queens are better adapted to local conditions.

Robbing brood and making nucs

There are at least two additional, and related, ways of increasing the space available so helping swarm prevention in a rapidly expanding colony.

The first is stealing a frame of brood 13 and using it to boost a weaker colony.

Take care when doing this.

If the recipient colony is weak due to disease or a failing queen then you’re just wasting the donated brood. However, if the colony is healthy but small it can be a good investment of resources and may help delay swarming in the donor colony as well.

More drastically, it may be possible to remove a frame (or perhaps even two) of brood and adhering bees to make up a nucleus colony. In my experience, a strong donor colony can almost always be used to produce a nuc without compromising honey production, and with the added benefit of delaying swarm preparations.

I’m going to write about nuc production in more detail in a few weeks as it deserves a full post of its own. It’s worth noting here that the nuc should also be provided with sufficient bees and stores to survive and you will need a queen for it (or at least a queen cell).

Do not just dump a couple of brood frames and bees into a box and expect them to rear a half-decent queen on their own.

However, if you have a queen (or mature queen cell) then splitting a nuc off a strong colony is usually a win-win solution for swarm prevention.


 

Who’s the daddy?

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

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

How do you measure polyandry?

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

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

Search and ye shall find – detecting rare patrilines

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

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

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

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

Half-sisters and super-sisters

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

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

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

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

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

Emergency queens and nepotism

What’s the most important decision a colony makes?

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

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

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

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

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

Do worker bees exhibit nepotism when rearing emergency queens?

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

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

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

Royal patrilines

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

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

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

Experimental details

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

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

The nucs then started rearing new queens … again.

And again … and again.

This process was repeated until the nucs failed.

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

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

Cryptic “royal” subfamilies

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

Subfamily distribution per colony.

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

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

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

Frequency distribution of subfamilies.

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

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

Implications for our understanding of honey bee reproduction

Two points are immediately apparent:

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

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

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

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

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

Who’s the daddy?

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

Mechanistically, what accounts for this?

Are these larvae selected solely because they are rare?

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

Perhaps it is not even worker selection?

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

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

Or whether they’re the wrong questions entirely.

Swarming and supercedure

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

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

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

Play cups

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

Queen rearing

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

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

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

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

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

3 day old QCs ...

3 day old QCs …

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

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

Are these accepted less well by the nurse bees?

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

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

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

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


Colophon

Ray Winstone (as Carlin) 1979

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

Polyandry and colony fitness

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

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

Colony fitness

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

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

Shallow depth of field

One of many …

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

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

The benefits of polyandry

Why should colonies with increased genetic diversity be fitter?

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

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

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

Does polyandry contribute to Varroa resistance? 

Would increased polyandry result in improved resistance to mites?

Limits of polyandry and natural resistance

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

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

How could this be tested?

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

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

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

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

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

Yes.

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

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

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

Brood frame with a good laying pattern

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

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

Natural Varroa resistance and polyandry

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

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

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

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

Marked queen surrounded by a retinue of workers.

Her majesty …

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

No.

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

On average, Arnot Forest queens had mated with ~18 drones (17.8 ± 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 …


 

Bee bombs

The last couple of posts on overwintering survival and local bees have been heavy going 1. So, rather than more of the same, here’s something that is both informative and entertaining 2.

Though it maybe wasn’t at the time.

Six-legged soldiers

I’m currently enjoying reading Six-legged soldiers by Jeffrey A. Lockwood. This is an account of the many and devious applications man has found for employing insects in warfare. Whilst the topic certainly isn’t ‘laugh out loud’ entertaining, the book is written in an engaging style with plenty of graphic descriptions, ample Biblical and historical references, and enough wriggly, stinging, aggressive insects to make “I’m a celebrity, get me out of here!” 3 appear like a walk in the park.

As a beekeeper I’m pleased to see that bees feature significantly in the book.

And as a beekeeper who appreciates the importance of the integrity of the colony to bee survival I also found it a little distressing.

But as a source of all sorts of stories for friends and families over the forthcoming holiday season it probably cannot be beaten.

It’s pretty good on mosquitos as well …

Bombus away

The genus Bombus includes lots of the well known bumble bees e.g. Bombus terrestris (Buff tailed), B. pascuorum (Common carder) and B. hypnorum (Tree) . The generic name Bombus is derived etymologically from the Latin word bombus which means buzzing i.e. the noise a bee makes when it flies.

Bombus lucorum

Etymologically, the word bomb, has a similar origin – via bombe in French, bomba in Spanish, bombo and then the Latin bombus.

Boom also has a similar origin.

But that’s not the only link between bees and bombs.

Mushroom shaped clouds

Have you ever seen anyone drop a full brood box?

It is an amazing sight and one best appreciated from a distance and when wearing a full beesuit.

Bees do not appreciate being knocked, shocked or jarred. When I transport hives between apiaries I always give them several minutes to settle before removing the entrance block. If you don’t they tend to boil out the front spoiling for a fight.

So you can imagine that dropping a brood box from waist height achieves – simultaneously – the sudden jarring of the colony and the release of the bees.

Not so much ‘shock and awe‘ as shock and aargh!

The mushroom-shaped cloud of bees that are released are distinctly agitated.

In the absence of a beesuit you’re likely to get hammered.

Even with a beesuit there can be some uncomfortable moments.

And, since soldiers don’t routinely go into battle wearing camouflage BBwear battledress with an inbuilt fencing-style veil, this neatly brings us to using bees as weapons.

Package bees

These days a ‘package’ is one way to buy bees to start a colony.

But as a weapon, a colony of bees isn’t much use until it’s actually in something.

How do you carry them? How do you use them as a projectile?

Well, man is nothing if not ingenious when it comes to weapons development.

The Tiv people of Nigeria used a specially shaped horn, loaded with angry bees (presumably not so much Africanized as African 😯 ). In the heat of battle these would be fired at the opposition, with the horn-shape ensuring the bees both reached the enemy and were kept at a distance from friendly forces 4.

But then, 9000 years ago, pottery containers started to be used for beekeeping … and it got a whole lot easier to move the bee bombs to the front line and drop them on the opposition.

A big, beautiful wall

A wall seems like an obvious way to defend yourself.

The enemy have to knock the wall down, or go over or under the wall.

And if they choose to tunnel under the wall then they’re going to be less than enthusiastic if the tunnel is filled with bees.

Which is what happened in 908 when the Scandinavians laid siege to Chester. The city’s fortifications were impenetrable, so they tunnelled underneath them. The siege was ended when all the city’s beehives were dumped into the tunnel.

Chester City walls. Originally built in ~100 AD by the Romans.

The Scandinavians appear not to have learnt their lesson as they were again repelled by bees while storming the walled city of Kissingen (Germany) during the Thirty Years War (1618-48). In this instance the bees were dropped from a height onto the Swedish forces.

The troops were heavily armed and armoured, and were unfazed.

Their horses were not.

The siege collapsed as the cavalry mounts were driven into a frenzy by the bees. Even now, most beekeepers are aware that bees and horses don’t mix well.

Again in the 1600’s, the besieged nuns of Wuppertal (Germany) knocked over all the hives in their apiaries before – wisely – hiding indoors. The maelstrom of bees drove the marauding soldiers away and the town was subsequently renamed Beyenberg (‘bee town’).

Bee boles

A bee bole is a recess in a wall 5 designed to house a hive of bees, which – in the days when they were constructed – was likely a skep. Many castles and fortified town walls have bee boles built into them.

How convenient.

What could be easier than to drop these on the marauding troops trying to scale the ramparts or storm the drawbridge?

Bee boles in Kellie Castle, Fife, Scotland

As an aside, IBRA (The International Bee Research Association) maintain the comprehensive Bee Boles Register which is well worth searching if you are interested in historical beekeeping (or early bomb design).

Avoiding friendly fire

You’ll notice that a lot of these bees were being used in relatively close combat situations.

Having witnessed a brood box being dropped, I can assure you that bees are rather indiscriminate after a “dropped from a great height onto a hard surface” experience.

Far better to use the container housing the bees as a projectile, launching them at the opposition from a safe distance.

Safe in terms of contact with the enemy … and the bees 😉

The Greeks and subsequently the Romans developed and perfected the siege engine, capable of launching all sorts of things up and over defensive walls.

Including beehives.

Illustration of a ballista being loaded and drawn – note BBwear ‘Corinthian helmet’ style beesuit and veil.

The Greek ballista and the Roman onager were torsion powered siege engines developed between 400 BC and 350 AD. Both were capable of firing stones, often wrapped in combustible material set alight, with smaller later models also used as battlefield weapons firing projectiles 500 – 1000 yards.

They’d have barely broken a sweat firing one or more skeps at the enemy.

The Romans were so keen on bee bombs that there was a documented decline in hive numbers during the late Roman Empire.

And this enthusiasm continued … as did the demand for hives to hurl.

By the 14th Century those dastardly weapons designers had developed a windmill-like device capable of launching hive after hive from the end of its rapidly rotating arms.

Bees will not fly over water

But they will in a skep catapulted from a ship.

As the army developed entomological weaponry the navy exploited it.

As early as 330 BC pottery hives were being thrown at enemy ships during naval battles. Cannons and cannonballs eventually superseded 20,000 A. mellifera ligustica in a skep, but there is well-documented use of bees in naval warfare until at least the 1600’s.

Bees would therefore have been carried by warships for hundreds of years. It’s not documented how the colonies were managed or maintained. Perhaps they only fought local battles? However, since that rather defeats the purpose of a highly mobile navy it can be assumed that bees were probably transported long distances by sea … bringing a whole new meaning to the term migratory beekeeping.

Gunpowder and bees

Eventually the development of modern weaponry overtook the use of bees and beehives. Fortunately we don’t have to discuss the aerodynamic benefits of cedar vs. poly hives 6.

Gunpowder and explosives made the Gatling gun-like skep-launching windmill catapult a relic of the good old days of warfare, when the infantry hankered after really cold days when the bees would be torpid and much less aggressive.

But, as a couple of masochists have already demonstratedApis mellifera is pretty tame where stinging is concerned.

Apis dorsata, the giant honey bee of South East Asia, is much bigger than our honey bee, and is reputed to pack more of a punch when stinging 7.

These bees build large exposed nests and the colony may have up to 100,000 bees in it.

Apis dorsata nest, a single exposed comb which may be a metre wide.

Which doesn’t mix too well with gunpowder or, more specifically, a firecracker containing gunpowder.

During the Vietnam War the Viet Cong would attach firecrackers to dorsata nests relocated to the jungle trails used by the enemy. As a patrol passed by they would ‘light the blue touch paper’ and set off the firecracker.

And then stand well back.

And, at about the same time (1960’s), the Americans were developing chemical warfare approaches using isopentyl acetate, the alarm pheromone, with the intention of spraying it onto enemy troops and redirecting the bees to attack them instead.

Six-legged soldiers

There’s lots more in Six-Legged Soldiers … get a copy and enjoy reading it over the Christmas vacation. Jeffrey Lockwood is an entomologist and University of Wyoming Professor. The Sunday Times 2009 review of the book criticised it as ‘scarcely scholarly’, being a mix of myth, legend and historical facts.

I cannot imagine a better review and it probably explains why it is so entertaining to read 🙂

Mite bombs

These are something altogether different to bee bombs … and for regular beekeepers, much more relevant.

A mite bomb is a heavily mite infested and collapsing colony that liberally spreads Varroa mites around the neighbourhood. Recent evidence suggests that this occurs primarily during late-season robbing of weak (mite infested) colonies by strong colonies.

This is the primary reason late summer miticide treatment should be coordinated over a wide geographic area. What’s the point of treating your strong colonies if they’re going to load up on mites when robbing weak colonies in the adjacent fields?

Which reminds me, and should remind you, that winter mite treatments will be needed in the next few weeks to ensure your bees get the best possible start to the new season.

We’ve had a protracted cold period here in Fife and my colonies will probably be treated in the next 5-7 days before there’s a chance they start brood rearing again.