Category Archives: Behaviour

More droning on …

Synopsis : Drones are now being evicted from colonies. How and why does a honey bee colony regulate drone numbers?

Introduction

Over the course of the last eight years posts on The Apiarist have got longer. This year, posts are now five times the length of the 2014 average. I’ve written – and hopefully, you’ll have already read – more words this year than are in The Hobbit.

If this continues until the end of the year we’ll have exceeded the word count in Tolkien’s The Two Towers.

This is probably unsustainable 1.

The increase is explained in part by the complexity of some topics. It’s compounded by the need to provide some contextual information … and by my prolixity 2. The latter is unavoidable, the former is probably necessary, not least because of the significant churn in new beekeepers.

A topic needs to be introduced, explained, justified and concluded.

Without this contextual information a post on oxalic acid trickling could be just:

5 ml of 3.2% w/v per seam when they’re broodless.

And where’s the fun in reading that?

Or writing it?

Furthermore, it’s probably of little use to a beginner who might not know what w/v means. Or what a seam is … or for that matter why being broodless is critical.

Keeping it topical

To maximise the income from site advertising I need to keep readers returning. This means the choice of topics should be important.

However, although some topics are chosen because they’re key concepts in the art and science of beekeeping, the majority are picked simply because I find them interesting.

And this week is one of the latter as I’m going to be droning on about … drones.

Specifically about drone numbers in the colony.

This was prompted by seeing the first drones of the season turfed out of the hive.

Dead drone at hive entrance

Another one bites the dust

Seeing this coincided with me discovering an interesting paper on how the queen’s laying history influences whether she produces drone or worker brood. This, inevitably, led me to other papers on drone production and discussions of how the colony controls drone numbers 3.

Drones are topical now because their days in your colonies are limited.

Already the colony will be producing significantly less drone brood than three months ago. The drones the colony has already produced will still 4 be flying strongly on good days.

However, when in the hive they will be being increasingly harassed by the workers.

Herding drones

If you open a colony very gently in the next few weeks 5 you might find the corners of the box contain high numbers of drones. The photo above was taken in late August and I’ve seen it several times late in the season. My interpretation is that it’s the only location in the hive in which drones can escape harassment by the workers.

Drone eviction

Drones ‘cost’ the colony a lot to maintain. A drone consumes about four times the amount of food than a worker (Winston, 1987). Therefore, once the fitness benefit of keeping drones falls below the expected costs needed to keep them they become ’surplus to requirements’. At this point the workers turf them out of the hive.

Evicted drones cannot feed themselves, so they perish.

It’s a tough life.

Interestingly, workers preferentially evict old drones. Presumably younger drones are more likely to fly strongly and mate with a virgin queen. Additionally, sperm viability in older drones is reduced, so their genes (and therefore those of the colony) are less likely to be passed on.

This ‘cost’ of maintaining drones is influenced by both the colony and the environment. For example, queenright colonies (which, by definition, have less need for drones) evict more drones than queenless colonies in the autumn, as nectar becomes limiting.

Although most beekeepers associate drone eviction with late summer/early autumn it also occurs when nectar is in short supply e.g. during the ‘June gap’.

It has also been suggested that drone eviction rates are related to colony size. Small queenright nucs, which have less need for drones, are more likely to evict than a full colony.

There’s still a lot we don’t know about drone eviction. For example, since drones tend to accumulate in queenless colonies, do these preferentially evict related drones to maintain potential genetic diversity in the population? 6

Hannibal the cannibal

Allowing an unfertilised egg to hatch, feeding the larva, incubating the pupa to emergence and then maintaining the resulting drone is a waste of resources if conditions are not appropriate. For example, doing this during a nectar dearth – particularly when drones are unlikely to be required for mating – makes no sense 7.

Therefore, in early spring and late autumn, workers cannibalise developing drone larvae. Effectively they are recycling colony resources. They preferentially cannibalise young larvae rather than older larvae. This makes sense as young larvae are going to need more food to reach maturity.

As above, queenless colonies cannibalise less queen-laid 8 drone larvae than queenright colonies.

In addition, some studies have shown that colonies with abundant adult drones cannibalise a greater proportion of developing drones. Again, this makes reasonable sense. Why rear more if you’ve got enough already?

However, to me it makes ‘reasonable’, but not ‘complete’ sense. Drones being reared as larvae are genetically related to the colony, adult drones may well not be. Drones that have drifted in from adjacent hives may therefore reduce the likelihood of the colony passing on its genes under environmental conditions which favour larval destruction but not eviction of adult drones.

Someone needs to look into this in a bit more detail 😉 .

There are lots of other aspects of larval cannibalism that are not understood. For example, how do workers discriminate between drone and worker larvae? Can they – as the queen can – measure the cell dimensions? Drone and worker brood pheromones differ from day 3 or 4. This seems a bit late to account for the cannibalisation of young larvae?

The influence of the queen

Since workers may cannibalise developing larvae 9 at different rates (drone vs. worker) it’s necessary to measure the colony’s egg sex allocation to see how the queen may influence drone numbers.

Only a few studies have done this …

There are experiments that suggest (they’re not definitive) that queens in continuously fed colonies lay more drone eggs in spring and summer than in autumn. This implies that day length or temperature may influence the queen, but it could also be a response to colony strength i.e. the queen lays more unfertilised eggs in a colony increasing in size, than in one decreasing.

In addition – and this is where I started down this rabbit hole in the first place – the egg laying history of the queen influences her current egg laying activity.

This easy-to-understand study was conducted by Katie Wharton and colleagues (Wharton, 2007). They confined queens for a period on either drone (DC) or worker comb (WC) – ensuring the queen could only lay drone or worker eggs for 4 days. They then transferred the queens to frames containing a 50:50 mix of drone and worker comb and recorded the amount of drone or worker eggs laid over 24 hours.

WC queens laid more drone eggs but the same amount of worker eggs as DC queens

There was a marked difference in the egg laying activity of the DC or WC queens when given the choice of laying drone or worker eggs. Although both the DC and WC queens laid similar amounts of worker eggs, the WC queens produced significantly more drone eggs as well.

Egg laying history or drone brood quantification?

This is a good study. The authors controlled for a variety of factors including season, colony size and food availability.

They additionally excluded the possibility that the egg laying activity of the queen was influenced by preferential cleaning of particular cells types by the workers, or by the workers backfilling certain cell types with nectar.

Finally, Wharton and colleagues allowed the colony to rear the eggs laid to pupation. The bias already observed was retained i.e. colonies headed by WC queens reared significantly more drone pupae than those headed by DC queens. The workers did not ‘correct’ the negative feedback exhibited by the WC queen, for example by preferentially cannibalising drone brood.

Although I termed this the ‘egg laying history’ of the queen a few paragraphs ago there is another interpretation.

The worker or drone comb already laid up by the queen – during the 4 day confinement period – remained in the colony. It’s therefore possible that the egg laying activity of the queen was influenced by the amount of drone brood already present in the colony.

Either explanation is intriguing.

How does the queen ‘count’ the number of drone or worker eggs she’s laid in the recent past? Alternatively, how does she quantify the amount of drone brood in the colony?

But what about the workers?

The Wharton study largely excluded the possibility that there was preferential cleaning of drone or worker cells by the workers in the hive. In fact, earlier studies have indicated that cell cleaning continues almost constantly and workers were equally likely to clean worker or drone cells.

The Wharton study also addressed – and excluded – the possibility that differences in the backfilling of drone or worker cells might influence egg laying.

However, it’s not understood what determines whether drone cells get backfilled with nectar by workers. My colonies are starting to do this now. Do the workers fill drone cells with nectar because the queen hasn’t laid in these cells or because they only backfill drone cells late in the season?

The former suggests that there is some sort of competition between the egg laying activity by the queen and nectar storage by workers. In contrast, the latter suggests that there are environmental triggers that influence this worker activity.

Or both … of course 😉 .

Comb building

In contrast to some of the studies outlined above, comb building is easy to monitor and – perhaps consequently 10 – has been well studied.

I’ve already discussed comb building in a recent post about queenless colonies. These preferentially build drone comb (Smith, 2018).

What else influences drone comb production?

Probably the two strongest determinants are the amount of drone comb already in the nest and the season.

Drone comb production is reduced in colonies that already contain lots of drone comb. Many beekeepers never observe this as they only use frames containing worker foundation. The workers squeeze in little patches of drone comb – often in the corners of the frame – but it never exceeds 5% of the total.

Colonies often prefer to build drone comb when given the choice

In contrast, natural nests contain 15-20% drone comb. That’s equivalent to two full frames in a National-sized hive. Once drone comb approaches this level a negative feedback loop operates and the workers build less drone comb. The negative influence of this drone comb (on building more drone comb) is enhanced if the comb contains drone brood.

Colonies drawing comb now (and certainly in the next month or two) will build worker comb. Some beekeepers exploit this to get lovely new worker frames drawn – nucs are particularly good at this 11. In contrast, drone comb is drawn in spring and early summer. The season – presumably day length and temperature – therefore influences drone comb production, and hence drone production.

A thousand words

Well, nearer 2000.

As we near the end of the season we start to see drones evicted from our colonies. It’s interesting to think about the interplay of events that resulted in the colony producing those drones in the first place … and how and why the colony regulates drone production throughout the season.

Wharton (2007) neatly summarised the five stages from comb building to adult drone eviction.

Drone production and maintenance in a honeybee colony

I’ve dealt with these in reverse order because that was the best fit with the photo of the dead drone on the landing board that I started with.

There’s a lot we still don’t understand about the regulation of drone numbers. In particular, I think the majority of studies have ignored the influence of adult drone numbers on any of five stages illustrated above.

This is an important omission as drones move more or less freely between hives. That means that adult drones may well be genetically unrelated to the colony.

Perhaps this means that adult drones do not influence drone production? After all, if they did negatively influence drone production – as suggested above – it would potentially limit the ability of a colony to reproduce its genes. Evolutionarily this doesn’t make sense (at least, to me).

There are a couple of studies that have tried to determine the influence of adult drones, but they have produced conflicting results. Rinderer (1985) added drones to a colony which consequently reduced drone brood production. However, Henderson (1994) did the opposite and showed that removal of adult drones had no effect on drone brood production.

There’s clearly lots more to do …


Notes

I wrote this late on Thursday night. While doing so I watched the page views of my four year old post on Mad honey go ‘off the scale’ (which for a beekeeping site means hundreds of views per hour). The interest wasn’t sparked by my erudite description of grayanotoxin intoxication. Instead it was related to a video of a ‘stoned’ Turkish brown bear cub rescued after eating honey produced from rhododendron nectar.

It’s now abundantly clear that if I want to maintain my outrageous advertising income I should probably write more about hallucinogenic honey and less about the evolutionary subtleties of honey bee sex ratio determination.

That’ll teach me 😉

References

Boes, K.E. (2010) ‘Honeybee colony drone production and maintenance in accordance with environmental factors: an interplay of queen and worker decisions’, Insectes Sociaux, 57(1), pp. 1–9. Available at: https://doi.org/10.1007/s00040-009-0046-9.
Henderson, C.E. (1994) ‘Influence of the presence of adult drones on the further production of drones in honey bee (Apis mellifera L) colonies’, Apidologie, 25(1), pp. 31–37. Available at: https://doi.org/10.1051/apido:19940104.
Rinderer, T.E. et al. (1985) ‘Male Reproductive Parasitism: A Factor in the Africanization of European Honey-Bee Populations’, Science, 228(4703), pp. 1119–1121. Available at: https://doi.org/10.1126/science.228.4703.1119.
Smith, M.L. (2018) ‘Queenless honey bees build infrastructure for direct reproduction until their new queen proves her worth’, Evolution, 72(12), pp. 2810–2817. Available at: https://doi.org/10.1111/evo.13628.
Wharton, K.E. et al. (2007) ‘The honeybee queen influences the regulation of colony drone production’, Behavioral Ecology, 18(6), pp. 1092–1099. Available at: https://doi.org/10.1093/beheco/arm086.
Winston, M.L. (1987) The Biology of the Honey Bee. Cambridge, Massachusetts: Harvard University Press.

Workers not shirkers

Synopsis : Not all foragers are equal. A small proportion – the elite foragers – make the majority of foraging trips. These are the most experienced foragers. Could pathogens and pesticides that reduce worker longevity compromise nutrition of the hive?

Introduction

All bees are the same.

Right?

No, of course not.

The three castes, from The ABC of Bee Culture, 1895

For a start there are three castes of honey bee; the queen, drones and workers … but we can also sub-divide these castes.

Queens

For example, most beekeepers would agree that there are fundamental and important differences between a virgin queen and a mated queen. They behave differently, their physiology is different and so are their their senses.

Drones

Similarly, the difference between virgin and mated drones is also pretty fundamental. In fact, it’s literally a matter of life and death 😉 . However, there are also less dramatic – largely physiological – differences between sexually immature and mature drones.

Workers

And there are differences in this caste as well.

Any beekeeper who uses Pagden’s artificial swarm for their swarm control has – although perhaps unknowingly – exploited the difference between two broad groups of workers; the hive (or nurse) bees and the flying bees (or foragers). The former are bees that have yet to fly from the hive. They rear the developing brood, look after the queen and perform a range of housekeeping duties.

After about three weeks the maturing worker goes on several orientation flights and eventually becomes a forager, responsible for collecting the pollen, nectar, resin and water the colony needs.

‘Eventually’ because workers undertake additional roles e.g. guard bees, undertaker bees and scouts, as they segue from hive bees to foragers 1. This change in roles during the lifetime of a worker bee is termed temporal polyethism 2.

Elite foragers

In this post I’m going to focus on the last of the roles the worker fulfils, that of foraging.

There is a lot of good observational and experimental science on foraging behaviour; for example, the preference of foragers for certain pollen or nectar sources, or the features of the colony that induces foraging activity. Some of this is briefly reviewed in ’A closer look – Foraging behaviour’ by Clarence Collison in Bee Culture 3.

Instead of rehashing those things I’m instead going to describe the concept of ’elite’ foragers. These are a minority of the forager population that do the majority of the foraging. They are therefore probably a very important cohort of bees for the colony.

The definition of elite foragers was first demonstrated for honey bees in studies conducted by Paul Tenczar working with Gene Robinson in 2014 4.

Gross differences in foraging activity was not a new concept. It had been observed in a wide range of eusocial insects in studies dating back to the 1970’s. Since reproductive fitness of eusocial insects – like bees, wasps and ants – is determined at the colony level, and workers are genetically related, variation in worker performance was neither expected nor had an obvious origin.

However, significant differences in worker performance are observed when suitable technology exists to detect it.

’We have the technology’ 5

Tenczar used RFID tags to label individual worker bees. I’ve described this technology before. It allows the unique identification of individual bees. Foragers were detected leaving or arriving at the hive by monitoring them with two RFID ‘readers’ arranged along the narrow hive entrance tunnel.

Theoretically at least, a bee registered by the inner and then the outer reader should be leaving the hive, whereas one registered first by the outer reader, followed by the inner, would be arriving. If these two pairs of events were separated by a several minutes it should mean the bee has successfully completed a round trip.

Unfortunately, the RFID/reader technology was in its (relative) infancy 6 and trips were missed. They even added two RFID chips to each bee to improve detection rates. Manual observation showed that there was a 76-94% chance of a trip being detected by at least one of the four readers. They therefore used reads rather than trips as a metric for activity level. This is a bit of a fudge but it will do for the purpose of this study.

As I will show shortly, the technology has now improved and there are more accurate ways to measure foraging trips.

Orientation flights and the age of onset of foraging

Tenczar et al., labelled over 1000 day-old workers in five separate experimental colonies and monitored their activity for 5-7 weeks.

Orientation flights occur before foraging flights, and usually take place in the afternoon. To be sure they were only monitoring foraging flights, they defined the first day of foraging activity as the one when there were at least 6 ‘reads’, and with at least 25% of reads occurring before midday.

Age at onset of foraging for tagged bees

The average age of a worker at the onset of foraging was 20.4 days – a figure in agreement with the ‘three weeks in the hive’ statement I made above. However, if you average the five separate lines of hive data (above) it is also clear that a significant proportion of the bees (actually 27% of them) started foraging within the first 10 days.

This is so-called ’precocious foraging’ and had been seen previously in colonies created with a single cohort of bees. The colonies used in these studies were small (~1000 bees in each) and were started with bees of all the same age. The fact that some start foraging precociously is a demonstration of the plasticity in temporal polyethism I referred to in an earlier footnote … and which non-scientists would describe as doing ‘different jobs at different times, that might vary’.

Workers and shirkers

However, just looking at the cumulative count of workers (above) it is clear that there is considerable variation in the timing of the onset of foraging.

In addition, and perhaps more surprisingly, the level of foraging activity also varied greatly.

Some workers made rather few foraging trips, others started early and finished late, making repeated closely-spaced trips throughout the day.

Contributions of individual bees to the total foraging activity in two colonies

These histograms show the relative foraging activity of RFID tagged bees in two representative colonies. The vertical axis records the number of bees making a particular relative foraging effort. The shape of the graph – large bars on the left and much smaller bars on the right – show that the majority of the bees (hence the large bars) do relatively little foraging, whereas a much smaller number of bees (in the shorter bars on the right) do lots.

Lorenz curves

A more informative way to represent this data is to use a Lorenz curve which displays the share of foraging activity (vertical axis) against the percentage of foraging bees (horizontal axis).

Example plot of a typical Lorenz curve of cumulative share of foraging activity for one of five study colonies

If all foragers contributed equally to foraging activity the ‘curve’ would be the diagonal dotted line i.e. 50% of the bees would ‘deliver’ 50% of the foraging activity.

In the colonies studied, the actual contribution to foraging activity is shown by the curved line.

Approximately 20% of the foragers accounted for 50% of the foraging activity (the area I’ve shaded blue). These are the elite foragers. Conversely, the ‘laziest’ 20% of foragers make less than 5% of the foraging trips (shaded red) 7.

These are the shirkers … the less said about them the better 😉 .

Tenczar et al., conducted additional analysis of the pattern of foraging activity per bee per day, and the consequences of removal of elite foragers (in due course other foragers become elite foragers). However, I’ll skip these as I want to move on to a more recent study of elite foragers.

We really do ‘have the technology’

In 2019 Simon Klein and colleagues published another RFID-tagged forager study 8. In the intervening years the RFID tag and reader technology had improved. They used two modified four frame nucleus hives in which bees traversed separate tunnels for entry and exit.

Colony entrance with sensors – bees enter and depart the hive using different tunnels

In addition to using more reliable RFID readers (#3 in the diagram above) they also weighed (#4) the bees as they entered and exited the hive and recorded video (#7) of the returning bees to determine whether they were carrying pollen.

These additional measurements meant that, in addition to the number of trips completed, the authors were also able to measure foraging performance in terms of pollen or nectar collected.

Actually, that’s a bit of an overstatement.

Pollen foragers were identifiable on video by their pollen-filled corbiculae (PDF). In contrast, foragers returning without pollen could have made unsuccessful trips, or may have collected nectar or water. They therefore classified foraging activity into ‘pollen’ or ‘non-pollen’ trips.

In total they monitored 564 foragers who made an average of 19 foraging trips in their lifetime (~10,500 trips in total). Interestingly, the average foraging lifetime was less than 5 days. As with Tenczar et al., they excluded orientation flights from the trips recorded (though in a different way).

Practice makes perfect

None of the bees monitored foraged exclusively for pollen. However, it was noted that the more trips a bee made, the greater the proportion of the trips were for pollen until a maximum was reached, after which pollen collecting declined.

Changes of foraging performance with experience – pollen collection (each line is an individual tagged bee)

Foragers lost weight on pollen foraging trips – presumably using crop contents to ‘fuel’ the flight. Since the weight of the crop contents were unknown, it wasn’t possible to calculate the weight of the pollen collected.

Non-pollen foragers weighed about the same (or a little more) upon return as when they left. Since both the weight of the crop contents and the identity of what was being collected (water or nectar) were unknown, it was not possible to determine how much had been collected. However, as individual bees aged – and so took more non-pollen foraging trips – their gain in weight per trip increased. This suggested that (as with the likelihood of collecting pollen) increased experience resulted in more efficient foraging.

The elite foragers are the best performing foragers

Analysis of the average number of foraging trips per day demonstrated that it increased over the first ten days and then plateaued at about 10 trips per day.

Changes of foraging performance with experience – average trips per day

It’s worth noting a couple of points here; firstly, on average foragers only made 19 trips in their lifetime and secondly, the majority of the foragers never reached maximal pollen foraging activity (in the multicoloured graph above, most lines terminate before they reach a peak and start to decline).

These points, together with the average foraging lifetime being under five days, indicate that there is a very high attrition rate amongst foragers.

Most die young … by which I mean within the first week of leaving the hive 🙁 .

But, some live long enough to become the experienced elite foragers, and these bees were the best performing foragers.

Like the previous study, an average of 19% of the foragers performed 50% of all foraging trips recorded 9. These were the elite bees.

These elite bees were the most likely to collect pollen and – on non-pollen trips – were most likely to show a gain in weight, indicating a greater resource (nectar or water) load was being carried.

Conclusions and consequences

The logical conclusion is that, through experience, bees improve their foraging performance. However, most bees never realise their full potential as they perish long before they achieve the status of elite foragers.

It is known that bees exhibit both learning and memory. With regard to foraging, it’s known that navigation skills improve with experience, and that both flower discrimination and ‘handling’ also get better i.e. they are more likely to find (and re-find) remote flowers, to distinguish them from other flowers in the immediate area and to harvest the pollen or nectar from the flower.

These elite bees must make a significant contribution to resourcing the colony.

Numerically they are a minority of the foraging population, but they collect lots of the pollen, nectar, water and propolis needed by the colony.

However, without knowing the precise number and age/experience distribution of the foragers and the mass of the pollen/nectar loads collected, it is not possible to determine whether they collect the majority of these resources.

For example, do 1000 inexperienced foragers collect more (or less) than 100 elite foragers? Are the massed ranks of young naïve foragers more effective at provisioning the colony than a few dozen of ‘old timers’?

We don’t know … yet.

The experiments needed to determine this are more difficult, and a lot more intrusive. You need to know both the weight of whatever was collected, together – in the case of pollen and nectar – with its value to the colony. For example, we know that bees preferentially forage on particular high protein pollens, or on high-sucrose nectar sources … presumably (though it needs to be shown) elite bees do this better than naïve foragers.

Looking after the elderly

Tenczar et al., showed that depleting the elite bee population had little long-term effect, because younger bees made additional foraging trips in subsequent days. However, this ‘replacement’ was only measured in terms of foraging trips, not foraging efficiency (which Tenczar didn’t measure).

If efficiency comes with experience – as suggested – it may be that additional time would also be needed to turn these extra flights into foraging trips that significantly benefitted the colony.

All of which means that stressors that adversely affect ageing bees, or that shorten the lifespan of foragers, may have a marked impact on colony pollen and nectar collection.

And there are lots of these sorts of stressors … pesticides, pollution, poor nutrition and pathogens – an alliterative gamut of threats to these important, elderly but highly effective bees. For example, increasing cumulative exposure to sub-lethal levels of pesticides may be deleterious to older bees.

Deformed wing virus

Unsurprisingly, being a virologist, it is the pathogens that interest me. In particular, deformed wing virus (DWV).

DWV symptoms

DWV symptoms

DWV is probably responsible for the majority of overwintering colony losses because it reduces the longevity of the (nominally long-lived) winter bees. I’ve discussed this at length elsewhere but the important bits are as follows:

  • winter bees should live for months, not weeks, maintaining the colony through until springtime
  • if there are lots of Varroa present during the early autumn (when winter bees are being reared) the developing winter bees will have high levels of DWV
  • some bees will die before emergence, but those that don’t will instead die in weeks, not months
  • consequently the winter cluster shrinks rapidly in size, becomes unable to thermoregulate and is separated from its stores
  • this doesn’t end well … the colony either dies, or struggles through to the spring and is too weak to expand

But what happens to foragers with high levels of DWV in the summer?

Studies from my lab 10 have shown that pupae injected with DWV – essentially recapitulating what Varroa does when it feeds on a developing pupa – have three potential fates; they either die during development (~15%; see B in the figure below), emerge with developmental abnormalities (~65%; the deformed wing bit which ’does what it says on the tin’) or emerge and appear ‘normal’ (~20%).

Unanswered questions

Interestingly, the small proportion of bees that appear ‘normal’ have indistinguishable levels of DWV to those that have deformed wings (panel A below).

The fate of bees injected with DWV

Do these bees with high-DWV levels live long enough to become foragers?

We don’t know.

If they do become foragers – which , frankly, I doubt – do they learn how to forage well?

Again, we don’t know, though we do know from other studies that high levels of DWV leads to some cognitive impairment, so navigation at least may well be suspect 11.

Finally, if they do become foragers, do they live a long and healthy life, or do they die prematurely?

Unfortunately … we don’t know this either.

Hive inspections

That’s a lot of ‘ifs’ there … and just as many unanswered questions.

Let’s assume that bees with high levels of DWV can mature to become foragers, but that they exhibit reduced longevity. If that is the case then the elite forager population would be reduced, so jeopardising provisioning the colony with nectar and pollen.

I’m sceptical that bees with such high DWV levels can survive long enough to mature into elite foragers. Nevertheless, I’d prefer to test this experimentally in the comfort of my lab 12, rather than in my honey-production or queen-rearing colonies.

Therefore, during hive inspections I look carefully for the signs of overt DWV disease or varroosis – bees with deformed wings, uncapped developing brood or phoretic mites. I also periodically measure mite drop. If I see see problems (and with correct timing and appropriate treatment in autumn and winter you shouldn’t 13 ) I intervene.

Midseason mite management may save the elite foragers … and help prevent the loss of the colony overwinter.

A gradation of DWV levels

However, there’s a related – more subtle – thing to consider.

Studies from our group (and others) have shown that injection of tiny amounts of DWV results in a very rapid replication of DWV to stratospherically high levels. As shown above, these kill or maim ~80% of exposed bees.

But there’s a less well understood feature of colonies with high Varroa levels. During the course of the season the levels of DWV in bees not exposed to Varroa during development rise.

In March or April, DWV levels may be ~103/bee 14. This is about the lowest level we ever see in bees, and is equivalent to the levels of DWV present in colonies from Varroa-free regions like Colonsay.

However, by mid- or late-summer the levels are 100-1000 times higher i.e. 105-106/bee 15. This is still 10,000 times lower than the levels DWV reaches in Varroa-parasitised pupae 16.

As an aside, we don’t formally understand how the DWV levels increase during the season. I suspect it’s through trophallaxis though we have also published some evidence of larval susceptibility to DWV during feeding.

Whatever the mechanism, bees carrying one million copies of DWV look completely normal and, as far as we can tell, behave completely normally.

‘As far as we can tell’, as no one has really done the right experiments …

I think it would be very interesting to carefully investigate the longevity and ability to achieve elite forager status for early season (very low DWV levels) and midsummer (intermediate DWV levels) bees.

Perhaps these intermediate levels of DWV are damaging after all?


Note

The Klein et al., paper has been very poorly proofread 17 and contains several errors, some of which potentially change the meaning of the text.

And then there was calm

Synopsis : The rush and bustle of the first half of the season is over and things are calming down. Time to reflect on some aspects of the season so far, and the importance of keeping good hive records.

Introduction

Over the past few seasons I’ve noticed that there is an inflexion point in the beekeeping season. It usually occurs a bit after the summer solstice, though the precise timing is variable. This is the time when I realise I’m no longer ’just keeping up’ (or sometimes ‘not keeping up’), but am instead finally ’in control’.

Perhaps those aren’t the correct terms?

It’s the point at which my beekeeping undergoes a significant change, from being ’reactive’ to something a whole lot more relaxing.

Late June and – both amazingly and reassuringly – I know what’s happening in those boxes

The variable timing of course reflects the behaviour of colonies in the preceding weeks; the early spring build up (Is it fast enough?), the – often startlingly rapid – mid-spring expansion and consequent swarm preparations, swarm control, queen mating (Has she? Hasn’t she?), the spring honey harvest and the need for additional feeding during the June gap.

All of which of course depends upon the weather and forage availability, explaining the variable timing.

And then, almost like a switch has been flicked – and with very little fanfare – the apiary feels a lot calmer.

There are no unexpected swarms hanging pendulously in nearby bushes, no real surprises when I open the hives, and no ’catch me if you can’ virgin queens scuttling about.

Instead, the bees are just getting on doing exactly what they should be doing and – significantly in terms of my reactive vs. passive beekeeping – exactly what I expect them to be doing.

It’s all downhill from here

As I left one of my Fife apiaries on Tuesday evening I realised that we’ve just passed the inflexion point this season.

All the colonies were doing pretty well. Laying queens were laying well, though not as fast as a month ago, foragers were starting to return with increasing amounts of summer nectar 1 and supers were beginning to fill.

Of course, not every hive is at exactly the same stage. A few are queenless, or contain unmated virgins. However, even these hives are behaving largely as expected.

Whilst it’s a bittersweet moment, it’s also reassuring to feel on top of things.

Bittersweet because it means the bulk of the beekeeping’ in my ‘beekeeping season’ is over.

Hive inspection frequency reduces from once a week to once a fortnight or even every three weeks. After all, the colonies are queenright, the new queen is laying well and they’ve got space for brood and stores … what could possibly go wrong?

A few things … but they’re much less likely to go wrong in the second half of the season to the first.

Of course, that doesn’t mean that there’s not still work to do.

The summer honey harvest will be busy, or at least I hope it will. It’s just starting to pick up, with the blackberry and (often not very dependable) lime.

Blackberry

That’s followed by the season’s most important activity – the preparation for winter and Varroa treatment. Without these I might not be a beekeeper next year.

However, none of these ‘second half’ functions are likely to produce any unwanted surprises – it should all be plain sailing.

The enjoyment of uncertainty

My move from the east coast to the west coast of Scotland has resulted in new challenges – more changeable weather, different forage availability – and I’ve still got a lot to learn here.

In contrast, despite the inevitable season-to-season variability, I feel reasonably confident with my east coast bees (I still have bees on both sides of the country). Only ‘reasonably’ because they can still produce the odd surprise.

However, with every additional year of beekeeping, I’m much less likely to be faced with a ”What the heck is this hive doing?” situation between now and late September than from April to June.

Nothing to see here … an old play cup in a queenright colony

The challenges are one of the things I really enjoy about beekeeping. It keeps me on my toes. Identifying the problems and (hopefully) solving them improves my beekeeping.

Even not solving them – and there have been plenty of those over the years – means I learn what not to do next time.

For some situations I’ve got a long mental list of what not to do … though little idea of what I should do.

No worries … perhaps I’ll learn next year 🙂 .

Weather dependence and queen mating

Three weeks ago I mentioned one of my queen rearing colonies had torn down all the developing queen cells, probably in response to the emergence of a virgin queen below the queen excluder. The box was set up with a Morris board, so was rendered queenless while starting the queen cells, and then queenright when finishing them.

One of the things this experience reinforced was the importance of continuing inspections on a queenright cell rearing colony.

Just because things all look OK above the queen excluder 2 doesn’t mean that it’s not all going Pete Tong in the brood box.

My records showed that I had checked the brood box on the 18th of May when I set up the Morris board. Grafts were added on the 25th and were capped on the 30th.

By the 1st of June they’d all been torn down 🙁 .

On finally checking the bottom box early on the 4th of June I found a virgin queen scurrying around.

Mea culpa.

The original queen had been clipped. The colony had presumably attempted to swarm around the time the virgin emerged – or perhaps a little earlier – and resulted in the loss of the clipped queen 3.

June rainfall, Ardnamurchan 2022

And then, as we segued into the second week of June, the weather took a turn for the worse.

Pollen

I watched for pollen being collected by foragers on flying days. It’s often taken as a sign that the hive is queenright. However, good flying days have been few and far between. I’d also been away quite a bit and there’s not a huge amount of pollen about at this point in the season.

However, is it a way to discriminate between queenright and queenless colonies?

I’ve watched known queenless colonies that are still collecting pollen, though perhaps at a lower rate than one with a mated, laying queen.

Do you remember the recent discussion about queenless colonies ’Hoping for the best but preparing for the worst.’ and preferentially drawing drone comb? Those drones will still need a protein-rich diet, so the colony – if it is to have has any chance of passing its genes on – will probably still collect pollen to feed the developing drones.

This particular colony was collecting pollen and was well behaved when I had a brief look on the 10th of June. My notes stated: ’Behaving queenright, but no eggs 🙁 .

On the 22nd of June, the next time the weather and my availability allowed a check, my notes were fractionally more upbeat: ‘No sign of Q or eggs, but no sign of laying workers either (let’s look on the bright side)’.

And then – on my next check – the 29th, there was a small patch of eggs, perhaps 2-3 inches in diameter 🙂 .

My notes this time were a bit shorter: ’Hu-bloody-rrah!’.

I also did some back-of-an envelope calculations which indicated that the egg used to rear the queen was probably laid on the 16th of May, and she was known to be laying 44 days later.

Flying days and mating days

I usually reckon – based upon published literature and accounts from much more experienced beekeepers – that a queen must mate within 4 weeks of emergence 4.

It looks like this one just met that deadline.

June temperatures, Ardnamurchan 2022

We had good weather in the first few days of June, but the middle fortnight was cold and/or wet, with the temperature rarely exceeding 14°C.

Assuming the queen emerged on the last day of May she probably probably went on her orientation flights in the good weather at the beginning of June.

As an aside, I’m not sure of the weather-dependence for queen orientation flights. For workers – based upon hive entrance activity – it’s pretty clear that they preferentially go on these flights on warmer days. However, if queens restricted themselves to good weather – particularly in more northerly climates – they might limit their chances of making successful mating flights. Perhaps queens go on orientation flights even if the weather is sub-optimal, so that they’re ready 5 when there’s a suitable ‘weather window’ for mating flights?

Anyway, back to this queen … I doubt she went on her mating flights in early June because there were no eggs in the colony when I checked on the 10th or the 22nd. My eyesight isn’t perfect, but I looked very carefully. There were definitely ‘polished cells’, but no eggs.

The temperature reached a balmy 19.4°C on the 24th of June (a day with only 7mm of rain!) and she was laying a few days later.

Being able to relate queen age with the weather helps determine whether she may have missed her chance to mate successfully. This is important in terms of the development of laying workers, or the colony management to avoid this.

The extremes of the season

For those readers living in areas where the weather is a lot more dependable this might not be something you ever think about.

Queens just get mated.

No pacing backwards and forwards in the apiary like an expectant father 6 waiting for the good news.

Lucky you.

But, there are times when this weather dependence might be relevant. Early or late in the season it’s likely that the weather will be wetter, windier and cooler. At those times you also need to think about the availability of sufficient (and sufficient quality – they decline later in the season) drones for queen mating.

Queen rearing – or queen replacement of a colony that goes queenless – might be successful, but is it likely to be dependably successful?

On the west cost of Scotland this enforces a ‘little and often’ regime to my queen rearing. Rather than using lots of resources to produce a dozen or two at a time I do them in small batches. Some batches fail – grafts don’t ‘take’, colonies abandon cells, queens fail to get mated – but others succeed.

Little and often – mini nucs (some balanced on an unoccupied – and now unneeded – bait hive)

I’ve got a batch of mini-nucs out in the garden now, and will probably try one or two more batches before the season draws to a close.

Our most dependable (and these things are all relative 🙂 ) pollen and nectar is the heather which is still a fortnight or so away. If that coincides with good weather then there’s a good chance for some late season queen rearing.

Global warming

But don’t forget global warming. This affects all beekeepers whether living in the balmy south or the frozen north. Global warming, and more specifically climate change, is leading to more weather extremes.

Extreme weather is becoming more frequent

Warmer, wetter and windier is the likely forecast. The first of these might help your queen mating, but torrential rain or gale force winds will not.

And that’s before you consider the impact on the forage your bees rely upon … which I’ll deal with another time.

More misbehaving queens

The conditions for queen rearing on the east coast of Scotland are far more dependable. I’ve been busily requeening colonies, making up nucs and clipping and marking mated queens for the last couple of months.

Most of this has all been very straightforward. All of it forms part of the ’reactive’ part of the season I referred to above.

If a colony makes swarm preparation I make up a nuc with the old queen and leave the queenless colony for a week. I then destroy all the emergency queen cells and add a mature queen cell or a frame of eggs/larvae – in either case derived from a colony with better genetics.

In due course the new queen emerges, gets mated and starts laying. I then mark and clip her.

This time last year I discussed a queen that fainted when I picked her up to clip her. That queen recovered, I clipped and marked her the following week without incident and she is still going strong.

Although I’d never seen it before, It turned out that several readers had experienced the same thing, so it’s clearly not that rare an event.

Pining for the fjords? 7

One of my good colonies – #38 in the bee shed – started to make swarm preparations in the third week of May. I removed the old queen to a nuc, left the colony for a further week and then reduced the queen cells, leaving just one which subsequently emerged on the 2nd of June (I also ‘donated’ one spare queen cell to a neighbouring hive that was also making swarm preparations).

Colony #38 wasn’t checked again until the 20th 8 when I found a good looking mated, laying queen.

I gently picked her up by the wings.

She didn’t feint 🙂 .

She died 🙁 .

That is an ex-queen

At least, I’m pretty sure she died.

She curled up into a foetal position and showed no movement for 15 minutes. There might have been a slight twitching of an antenna, but the regular expansion and contraction of the abdomen during breathing was not visible. I wasn’t even certain her antennae moved.

I had other hives to inspect so I popped her into a JzBz queen cage and left her with the colony whilst I got on with things.

When I returned – an hour or so later – she was still looking like an ex-queen.

I had little choice but to leave her lying on a piece of paper underneath the queen excluder 9. She was quickly surrounded by a group of workers.

Mourning or moving?

I closed the hive up, crossed my fingers 10 and went off to another apiary.

Like mother, like daughter

The following week the colony was indisputably queenless.

Their behaviour was less good and – a much more definite sign – they had produced a number of emergency queen cells from eggs the queen had laid. I knocked all the queen cells back and united colony #38 with another hive.

Uniting colony #38 with another after the queen ‘popped her clogs’

One week later they were successfully united.

Only later, when comparing my notes with last season, did I realise that the queen that died was a daughter of the queen that fainted last year. I wonder whether the ‘dropping dead’ is just a more extreme version of the fainting I had previously observed?

This implies it might be an inherited characteristic (as at least one of the comments to the fainting post last year suggested).

For clarity I should add that I’m certain that I didn’t directly harm the queen when I picked her up. She was walking around very calmly on the frame. I waited until she was walking towards me, bending at the ‘waist’ (either to inspect a cell, or crossing a defect in the comb) so pushing her wings away from the abdomen. I held her gently by both wings and immediately dropped her into my twist and mark cage.

No fumbling, no squeezing, no messing.

I’ve done this a lot and it was a ‘textbook example’.

Except she never moved again 🙁 .

And like sister?

If, as seems possible, this is an inherited characteristic it will be interesting to see whether the neighbouring colony I donated the spare queen cell (from colony #38) to also shows the same undesirable phenotype 11.

Not so much ‘playing dead’ and ‘being dead’ when handled.

The original fainting queen is currently heading a full colony in another apiary. I’ve had no cause to handle her since last June. She didn’t faint the second time I picked her up (for marking) but I might see how she reacts next time I’m in the apiary.

If she faints again, and particularly if the sister queen reared this season faints (or worse 🙁 ), I’ll simply unite the colony with another.

Firstly, it will be getting a bit late in the season for dependable queen mating and, secondly, it’s clearly an inherited genetic trait that I do not want to deal with in the future.

It doesn’t really matter how gentle, productive or prolific the bees are if the queen cannot cope with being (gently but routinely) handled. It doesn’t happen often, but the risk of ending up with a corpse when I manhandle her into a Cupkit cage, or have to repeat the marking, makes some aspects of beekeeping impractical.

Nicot Cupkit queen rearing system

But look on the bright side … it will be a very easy phenotype to detect and select against 😉 .

Hive records

If there is a take home message from these two anecdotes it’s that good hive records are both useful and important. They help with planning the season ahead and avoiding real problem areas of colony management.

I use a (now propolis encrusted) digital voice recorder (and spreadsheet) when inspecting multiple hives

Far better to know that the queen is almost certainly too old to mate than continue to hope (in vain) that it’ll work out. If you are certain – within a day or two – of her emergence date you can intervene proactively (e.g. by uniting the colony, or supplementing it with open brood) to delay or prevent the inevitable development of laying workers.

By also watching the weather you can also work out when she should have been able to get out and mate.

Similarly, by keeping a pedigree (which sounds fancy, but needn’t be) of your queens, you can avoid selecting for undesirable traits. These fainting/dying queens might be unusual, but there are other behaviours that might also be avoidable.

The original queen in colony #38 might have been a ‘one off’, but if her daughters also behave similarly then I should avoid using them to rear more.

To paraphrase Oscar Wilde, “To lose one fainting queen may be regarded as unfortunate, to lose two looks like carelessness poor record keeping”.


 

Bad behaviour

Synopsis : Bad behaviour by bees – aggression, following and stability on the comb – may be transient or permanent. To recognise it you need to keep records and have hives to compare. Fortunately, these traits are easy to correct by requeening the colony.

Introduction

That’s a pretty generic title and it could cover a multitude of sins.

Slapdash disease management, insufficient winter feeding, poor apiary hygiene, siting bait hives near another beekeeper’s apiaries … even bee rustling.

However, I always try and write about a topic from direct practical experience.

If I did ever exhibit any of those examples of bad behaviour:

So, instead of discussing bad behaviour by beekeepers, I’ll write about badly behaved bees.

Nice bees

Most beekeepers have an idea of what ‘nice bees’ are like. It’s a 2 term that encapsulates the various characteristics that a beekeeper values.

These characteristics could include temper, stability on the comb, productivity (in terms of either/both bees or honey), frugality, colour and any number of other terms 3 that define either the appearance or behaviour of individual bees or, collectively, that of the colony.

Of course, all these terms are relative.

Nice bees and a nice queen

My definition of aggressive bees may well differ from what another beekeeper would consider (un)acceptable.

The relatively calm and stable bees in most of my hives could be defined as ’running about all over the place’ by someone who’s bees stick, almost immobile, to the comb.

This relativity is nowhere more apparent than when visiting the apiary of another beekeeper. I’m always a little wary of someone donning a beesuit 100 metres from the hives 4 while simultaneously claiming their bees are ’very friendly’.

These differences don’t matter if you keep your bees in an isolated location where other people – in particularly civilians (i.e. members of the general public) – won’t be impacted if your ’friendly bees’ are actually ’murderous psychopaths’.

However, they do matter if your bees are in an urban garden, or a shared allotment.

They also matter when making comparisons between colonies to determine which to split (so creating a new queen) and which – perhaps urgently – need requeening.

Transient or permanent?

For the purpose of the following discussion let’s consider that the ‘bad behaviour’ is aggression.

Here’s a screenshot from a YouTube video (from CapLock Apiaries) which shows some really unpleasant bees. The final words (in this part of the video) by the beekeeper on the right is ”This queen has to die!”.

‘This queen has to die’ … beekeeping doesn’t have to be like this

The brood boxes were stuck together, presumably because the colony is less regularly inspected and everything gets gummed up with propolis. The first comment 5 was

I’m new to bees and thought I found a hot wild hive today. Went to youtube to find some comparison. The hive I saw was absolutely docile in comparison to these guys, and the first wild hive I extracted are absolute angels!

Which emphasises the relative nature of behaviour.

I dislike aggressive bees so have no videos of my own showing this sort of behaviour 6.

However, that doesn’t mean that my bees never show aggression … 😉

Weather, forage, handling, queenless … all can influence temper

Aggression – or defensiveness – can be a permanent feature of a colony or can appear transiently. In my view, the former is unacceptable under any circumstances 7.

However, in response to environmental conditions or handling, a colony may become defensive. Again, the amount of ‘aggro’ varies. Some bees may just buzz a little more excitedly, others can go completely postal. If you are careful to only select from your better behaved stocks for splits and queen rearing you can usually avoid even transient unpleasantness.

Environmental factors that can influence the behaviour of a colony include the weather, the availability of forage and the gentleness and care exhibited by the beekeeper during inspections.

Queenless colonies may also be more aggressive, but all the comments in the post this week relate to queenright colonies.

Scores on the doors

There are two easy to achieve solutions that allow a beekeeper to make sense of the variation in any of these traits. These are:

  • keeping good hive records to allow undesirable behaviour, or a gradual decline in behaviour, to be identified, and
  • managing more than one colony so comparisons can be readily made

I score temper, running (stability on the comb) and following, but I know some who record a much greater range of characteristics.

Each are recorded on a 1 – 5 scale (worst to best, allowing half points as a ‘perfect 5’ is unattainable as the bees can always be better, whereas a 4.5 is a really good colony).

The bees in hive #34 run all over the place. They are being requeened.

I also make a note of the weather. A colony may consistently score 4’s or better until you inspect them in a thunderstorm, but that’s OK because when you look back you’ll see that the conditions were woeful.

Compare and contrast

With just one colony you have no reference to know whether all colonies in the area are suffering because there’s a dearth of nectar, or if this colony alone is a wrong ‘un.

With two colonies things get easier.

Increasingly – for reasons I’ll discuss in a future post – I think three is probably the minimum optimum number.

The more you have the easier it is to identify the outliers … the exceptional (whether good 🙂 or bad 🙁 ). That should be qualified by stating the more you have in one location as the local environment may differ significantly between apiaries.

The great thing about hive records is that they provide a longer retrospective view. You can overlook the hammering you received from a colony last week 8 if there are a long list of 4’s over the last 3 months.

They also allow you to observe trends in behaviour.

Growing old disgracefully

I’ve recently noticed that a couple of my colonies are markedly less well behaved now we’re reaching mid-season than they were throughout 2021 or the beginning of this year. I think at least one has (actually had, as it was requeened last week) a 2020 queen.

As the queen ages the behaviour of the colony has gradually changed.

I crudely classify my colonies into thirds – good, bad or indifferent. Anything ‘bad’ is requeened as soon as I have a suitable queen available (or the larvae to rear one).

These ‘declining’ colonies were never worse than indifferent last year but, as they’ve expanded this spring, are now firmly in the ‘bad’ category. I presume this is consequence of the combination of the influence of the queen’s pheromones and the size of the colony 9.

Whatever … I think all it really demonstrates is that consistently taking even cursory hive records is useful.

The colonies I’m referring to above haven’t become more aggressive (though this can happen). The characteristic I’ve seen change the most is the steadiness of the bees on the comb.

It’s worth noting here that colony size can fundamentally impact behaviour. A well-tempered nuc can develop into a big, strong and unpleasant colony. In contrast, the nucs I prepare from ‘indifferent’ colonies during swarm control and requeening don’t appear to generally improve much in temperament.

If I’m conducting swarm control on the third ‘bad’ tirtile 10 the queen is despatched so I never get to experience the performance of the resulting nucleus colony 😉

Aggression

I’ve discussed aggression above and covered it in more general terms previously. There are several studies of the genetics of aggression, usually by GWAS (Genome Wide Association Studies) of Africanised bees which can be significantly more bolshy than anything I’ve encountered in the UK 11. The colony shown in the video cited above is Africanised.

A recent study analysed individual aggressive bees 12 and compared them with pollen-laden foragers from the same colony. However, they failed to identify any genetic loci associated with aggression.

In contrast, by ‘averaging’ the genetics of hundreds of aggressive or passive (forager) bees, the scientists identified a region of the genome that – if originating from European honey bees – was more likely to result in gentle bees. Conversely, if this region is Africanised, the colony was more likely to be aggressive 13.

Hive genetics, not individual genetics

This is a really interesting result 14 as it means that, even if individual bees are Africanised and potentially aggressive, if the majority of the colony is European-like (and so gentle) the individual Africanised bees are unlikely to be aggressive.

Aggression is therefore a consequence of hive genetics, rather than individual genetics.

Neat.

Aggression in psychotic UK colonies (which, by definition, are not Africanised) may have a different genetic explanation, though some of the genes involved may be similar. Since aggression can manifest itself in several different forms – jumping up from the frames, buzzing around your head, response to sudden movement, targeting dark colours etc. – I suspect there may be multiple genes involved in the sensing or threat response.

Following

Some aggressive bees – particularly those that buzz agitatedly around your head during an inspection – also have the profoundly unpleasant trait of following you out of the apiary … down the track … back to the car … or even into the house.

The car is packed, you’ve taken you beesuit off … and PING!

The very worst of these lull you into a false sense of security by flying off, only to return in a lightning-fast kamikaze strike as soon as you remove your veil.

Ouch, that hurt.

I consider ‘following’ a worse trait than overt aggression at the hive.

I’m suited and booted’ at the hive. Ready for anything … ’Come on if you think you’re hard enough’.

At least, I am if I’ve remembered to zip my veil up properly 😉

But 15 minutes later, when I should be contemplating a cuppa, I don’t want to be pestered by bees dive bombing my head.

Looking for trouble

Followers don’t necessarily just follow.

They can initiate long-range and unprovoked attacks on individuals just walking near the hive.

I think this is an example of bad behaviour that should not be tolerated.

If you think it’s bad as a beekeeper, just imagine how unpleasant it is for passers by.

Sometimes it’s difficult to identify which of several hives is showing this trait in an apiary. To confirm it, change the order of hive inspections, leaving the likely suspect to last. If the followers don’t appear until the final inspection you have your answer.

If they’re present before that you either guessed wrong or – Eek! – have more than one hive behaving badly.

I’ve seen many aggressive colonies that showed little or no tendency to follow. Conversely, I don’t remember seeing followers that were not from an aggressive colony. I presume this means that the genes involved are distinct but linked.

Whether different or not … they’re unwanted. Any colonies of mine showing overt aggression or following are requeened. Perhaps 5% of my colonies each season are requeened for this reason.

Running

Remember back to your early days of beekeeping when you had to ’find the queen’ and were faced with this … 15

Find the queen

I estimate there are about 1200-1300 bees on the face of that frame 16. There are the same amount on the other side.

All of the bees are moving.

Of course, this makes it much easier to find the queen as she moves differently to the workers on the frame. I’m probably not alone in sometimes struggling to ‘find the queen’ on a photograph of a frame when I rarely have trouble locating her on a frame in my hands 17.

However, the more the workers move, the more difficult it gets.

Spot the queen

See if you can spot the queen on this frame of relatively sedate bees:

And what about this frame of more mobile bees? It’s worth noting there are only about half the total number of bees on this second frame.

OK, I cheated. Only the first frame has a queen on it. She’s in the middle near the bottom of the frame, moving left to right 18.

The top frame is pretty standard in terms of ‘running’ (shorthand for the stability of bees on the frame) in my hives. The bottom video is nothing like the worst I’ve seen, but (if consistently like this) it’s certainly a reason to score the colony down and requeen them from a more stable line.

Inspections

Bees running around on the frame certainly make locating the queen more tricky.

However, as I’ve written elsewhere, you don’t need to find the queen unless you need to do something with her. The presence of eggs is usually sufficient to tell you the colony is queenright (assuming there are no big, fat queen cells or a queen corpse on the open mesh floor 🙁 ).

The reason I dislike bees that are not stable on the comb is because they make inspections more difficult. They prevent you clearly seeing eggs and larvae so you have to shake the bees off the frame, thereby overloading the next frame you look at with agitated bees.

Furthermore, the bees must have somewhere to run to … which usually means they run onto the frame lugs, and then your hands and – in the worst cases – up your forearms.

There was a frame lug there a few seconds ago

In addition, they run over each other, forming heavier and heavier ‘gloops’ 19 of bees that eventually become too heavy, lose their grip and fall … onto the top bars of the frames you have yet to inspect, onto the ground, or into the top of your boots.

A ‘gloop’ forming

Running appears to be a feature which isn’t influenced much by environmental conditions, perhaps other than a chilly and gusty wind 20.

Better bees

There are two good things about aggression, following and running:

  • these behaviours are easy to identify; you can easily tell if the colony is too hot for comfort, or if your neighbour complains repeatedly about getting chased by bees, or you’re plagued with ‘gloopy’ bees that make inspections a pain. Remember, there’s no standard to compare them to, no ‘reference colony’. All that matters is how they’re viewed by anyone that interacts with them. If they’re too defensive, if they bother you away from the hive or are too mobile, then score them down in your hive records. If they remain the same for the next two to three weeks, or don’t improve when the weather/forage picks up, then make plans to do something about it.
  • all these undesirable traits can be easily corrected by replacing the queen. Four to six weeks after requeening the characteristics of the colony will reflect those of the new queen. Of course, this only works if you source a good quality queen – either by rearing your own or purchasing one 21, or by ensuring that the colony raises its own queen from larvae sourced from a high quality colony. While you’re at it do yourself and your neighbouring beekeepers a favour and fork out any drone brood in the misbehaving colony.

It really is as easy as that.

Incremental but steady improvement

Over a few years the quality of your bees will improve.

Of course, with open mating you’ll occasionally get rogue colonies. However, as the average quality improves, you’ll have a greater choice of colonies from which to source larvae.

Over time you’ll need to recalibrate your scoring system. In five years a 3/5 will be a much improved colony over a 3/5 now.

When you next (reluctantly) open a bolshy colony, struggle to find the queen because of the wriggling mass of bees on the frames and are then stung repeatedly as you take your veil off by the car, think of it as an opportunity.

You have now recognised the problem and you already know the solution 😉


Note

I’ve chosen aggression, following and running as three easy to spot traits that can be, just as easily, fixed. There are other examples of bad behaviour that may well be unfixable. There’s a dearth of nectar in my west coast apiary until the lime flowers and robbing is a problem 22. Although robbing is a variable characteristic (amongst different strains of bees) I doubt it could be excluded completely by requeening. Selection would be time consuming, being dependent upon environmental conditions. However, the ‘fix’ is again relatively straightforward … keep very strong colonies, feed late in the evening (if needed) and physically protect colonies with reduced entrances and/or robbing screens. Robbing is an example of bad behaviour by bees where the solution is almost entirely the responsibility of the beekeeper.

The bees know best

Synopsis : Queens reared under the emergency response are numerous and preferentially started from eggs. The cells are then subjected to strong selection by workers after capping. What does this tell us about good quality queens and can we use this knowledge to improve our own queen rearing?

Introduction

In Eats, sleeps, bees I made a passing comment on the confidence I have in the ability of bees to choose ‘good’ larvae when rearing a new queen. I was justifying why I only leave a single queen cell in a colony that needs requeening. The precise words were:

“I also had total confidence that the bees had selected a suitable larva to raise as a queen in the first place. After all, the survival of the resulting colony depends on it.”

I thought this might be an interesting topic to look at in a little more detail. There is some interesting science on queen cell production.

And subsequent destruction.

Queen cells

Queen cells … have they chosen well?

In addition, there are related observations on what the bees choose as the starting material for queen cells. This should inform our own queen rearing activities. I’ll discuss these (briefly) after presenting the science.

Emergency, supersedure and swarm responses

But first I need introduce the three ‘responses’ under which a colony rears one or more new queens. These are the emergency, supersedure and swarming responses 1

The swarming response

Around this time of the season 2 many beekeepers will be familiar with queen cells produced under the impulse to swarm.

A strong, queenright colony runs out of space. Eggs are laid in specially created vertically oriented cells and are subsequently reared as new queens.

Once these swarm cells are sealed the colony swarms. The old queen and a significant proportion of the workers disappear over the fence. One or more new queens emerge and the colony may produce casts, each headed by a virgin queen. One new queen finally remains, gets mated and heads the original colony.

Swarming is honey bee reproduction … it is the only (natural) way one colony becomes two.

The supersedure response

Supersedure is the in situ replacement of the current queen. The colony produces a small number of supersedure cells – often just one, located in the middle of a central frame 3 – the new queen emerges, mates and starts laying. There may be two queens in the box for an extended period, but eventually the old queen disappears.

Supersedure is probably more common than most beekeepers think. It is the usual explanation for the presence of an unmarked queen at an early season inspection in a hive that had previously contained a marked queen.

The emergency response

If the incumbent queen is removed or killed the colony must rear another or they are doomed. They do this under the emergency response.

Some beekeepers – particularly beginners 4 – inadvertently crush the queen while returning brood frames. They are then surprised at the next inspection to find no eggs but a lot of queen cells.

What’s this? Swarming finished weeks ago!

This is the emergency response at work. The bees select several suitable eggs or larvae, reshape the comb to allow a vertically-oriented cell to be drawn and feed with copious amounts of Royal Jelly.

And voilà, a new queen 5 is produced.

Inducing these responses

The emergency response is triggered by the removal of the old queen – either by physically taking her out of the box, or killing her. Both are easy to achieve 🙁 6

There are ways to induce a supersedure response, but they sometimes involve damaging the queen 7 and are unreliable and – more importantly – ethically dubious. There are more ethically acceptable alternatives.

Lots of beekeepers inadvertently induce the swarming response by not providing the bees with sufficient space, not supering early enough or allowing the brood nest to be backfilled with nectar.

However, doing this in a controlled manner is not a certainty. In one of my apiaries 50% of the colonies have shown no inclination to swarm this season whereas the others all produced swarm cells. All were treated similarly and were – to all intents and purposes – of equivalent strength.

Sealed queen cells produced under the swarming response

For scientific purposes inducing a swarming response cannot be relied upon for studies of queen cell production and selection.

In contrast, the emergency response is 100% reliable. Therefore, in the majority of studies on brood choice, queen cell production and selection, it’s the emergency response that is exploited. That’s certainly the case with the two papers I’m going to briefly discuss this week. 8.

Pick a larva, any larva

Is that what the bees do?

Of course not.

Regular readers will remember from Timing is everything that only larva up to three days old are suitable for producing new queens i.e. six days after the egg is laid.

However, if the queen is laying 1000 eggs per day 9 that still means there are up to 3000 suitably aged larvae in the hive for the production of a new queen, should one be needed.

Eggs and young larvae

Eggs and young larvae

Actually there’s even more choice as the bees can start the queen rearing process – the production of a queen cell – from a cell occupied by an egg … something that has been known for decades, but is relatively rarely discussed.

So, what do they choose?

The first study I’m going to discuss addresses this point and the interesting (and critical) aspect of the quality of the resulting queens that are produced.

Hatch, S., Tarpy, D. & Fletcher, D. Worker regulation of emergency queen rearing in honey bee colonies and the resultant variation in queen quality. Insectes soc. 46, 372–377 (1999).

The study was very straightforward. They induced the emergency response by dequeening strong hives. They then monitored the production and position of queen cells over time, determining the age of the egg/larvae selected by extrapolating back from the day the queen cell was sealed.

Cells that were capped were caged with queen excluder and the resulting emerged queen was analysed to determine her quality. This essentially involved determining her size and weight (the bigger the better) and ovarial number, but they measured additional features as well.

Emergency cell production

In the 8 colonies used, almost all queen cell construction was started within 24 hours of queen removal. A few more cells were produced for up to 48 hours after dequeening, but none were started after that.

There will still be many hundreds of (apparently) suitably aged larvae in the colony at this point. However, these were not selected as all the queen cells that would be made had already been started.

Colonies produced different numbers of queen cells, from 6 to 56 (average 27).

However, the majority of these cells were torn down before emergence, and a few of those that were sealed never emerged. Of the 217 cells started, 115 (53%) were torn down, 11 (5%) did not emerge and the remaining 91 (43%) emerged.

Not only did the number of queen cells produced vary greatly between hives, so did the numbers of queens that emerged – from 3 to 20 (average 11).

The brood nest is roughly spherical or rugby ball-shaped and usually occupies the centre of the hive. About 46% of the cells started were on the central three frames, and these had a much greater chance of producing queens. This was because queen cells started on the central frames of the brood nest were less likely to be torn down (41%) than those on the periphery (71%).

Pick an egg or a larva (in which case, the younger the better)

So if it’s not Pick a larva, any larva’, what do the bees choose to start their emergency queen cells from?

Remember how important this is. Without a new queen the colony cannot survive. The clock is ticking. They only have a few days to make this choice before all the brood in the nest are too old for queen production.

The non-random construction of queen cells.

They predominantly choose eggs.

Almost 70% of queen cells started were initiated when the cell contained an egg, rather than a larva. What’s more, the majority of the eggs chosen were three days old.

If you consider that there were 6 possible choices (1, 2 or 3 day old eggs and 1, 2 and 3 day old larvae), it’s striking that 34% of all the queen cells produced were from 3 day old eggs.

In fact, it turns out that only five choices were made as none of the queen cells were started from 3 day old larvae.

Furthermore, over 60% of queen cells produced from 2 day old larvae were subsequently torn down.

Bees choose to make queens from the oldest eggs or the very youngest larvae.

Are you getting the message?

Since the production of a new queen is essential for colony survival we should assume that the bees have evolved a queen cell production ‘strategy’ that maximises the chances of producing a suitable queen.

Almost 60% of the ‘starting material’ chosen by the bees to ensure colony survival – that resulted in queen production – were 3 day old eggs or 1 day old larvae.

This emphasises the need to provide colonies we use for queen rearing with eggs and larvae of this age range. It also reinforces the importance of only selecting the smallest larvae possible when grafting.

The choice the bees make is presumably because queens reared from older larvae are of poorer quality, perhaps because they have a reduced period for feeding with Royal Jelly.

So how do the queens produced from eggs and young larvae compare?

Queen ‘quality’

Of the 91 queens that emerged only 89 were analysed because two ”escaped capture”.

It’s reassuring to know that it’s not just cackhanded beekeepers that make mistakes 😉

There were no differences in the morphology – weight or size – for queens that emerged from cells on either the central or peripheral frames 10.

However, queens reared from 3 day old eggs were significantly heavier than queens reared from larvae. In addition, queens reared from 3 day old eggs had a longer thorax than queens reared from either younger eggs or larvae.

Other morphological measurement – e.g. wing length or width – did not differ significantly between queens reared from eggs or larvae.

But are these hefty, long-thoraxed, queens better quality?

This isn’t a simple question. What does better quality mean? It’s not the size or productivity of the resulting colony she heads since that is also influenced by the genetics and number of drones she mates with.

It’s also time consuming and impractical to measure scientifically (for 89 queens).

Instead, the scientists measured the number of ovarioles and the volume of the spermatheca as potential indicators of fecundity. There was no relationship between weight and ovariole number, irrespective of the age of the egg or larva when the cell was started.

If not more fecund, what?

So, if bigger queens don’t necessarily have increased fecundity (though remember, this wasn’t shown – all they demonstrated was that the ‘innards’ involved in fertilised egg production were similar) why might the bees select eggs/larvae that resulted in bigger queens being produced?

One possibility is that these bigger queens have greater success in what is termed polygyny reduction.

This is what beekeepers call fighting.

If more than one queen is present they fight until only one is left in the hive. This hadn’t been extensively studied in 1999 (when this paper was published) but has been addressed in other studies 11.

Alternatively, and suggested in a tempting but cryptic ’unpublished data’, heavier queens may be able to achieve higher levels of polyandry i.e. mate with more drones, so increasing the genetic diversity, and consequently the fitness, of the colony. I’ve discussed the importance of polyandry and so-called hyperpolyandry for colony fitness and disease resistance previously, so won’t revisit these here.

It’s easy to speculate that a queen with a larger thorax may have better developed flight muscles. These might enable her to stay longer in drone congregation areas for mating.

Why are so many cells started (and queens reared)?

In the emergency response only one queen is needed to ‘rescue’ the colony from oblivion.

Why therefore are so many queen cells – on average 27 per colony – started?

And why do the workers allow an average of 11 queens emerge?

The authors suggest a number of possible reasons:

  1. Colonies raise multiple queens to guarantee the requeening process. This assumes that the ‘cost’ of queen rearing is low, which seems reasonable. Since only 5% of queens raised failed to emerge it is probably not to overcome this limitation.
  2. Multiple queens allow colony reproduction if conditions are suitable. Only colonies that raise multiple queens would be able to (simultaneously) reproduce and requeen, so there might be a selective pressure to allow this.
  3. A consequence of age demographics (brood or workers) in the colony. This is slightly trickier to explain and has not been tested. Queen cells result from an ‘interaction’ of available brood (eggs/larvae) with workers. A colony has variable numbers of both, and there are a variety of worker cohorts, only some of which contribute to cell building. Therefore, the production of multiple cells (and queens) may simply reflect the variation in the factors – ages of brood and workers – involved.
  4. Rearing multiple queens allows workers to select the ‘best’. That’s clearly wrong because the ‘best’ would be just one queen. Perhaps a better explanation would be that it allows workers to either select for better queens by destroying those that are less good.

No single reason

Biology is complicated 12 and it may be that all four of the reasons above are correct. There may be (and almost certainly are) additional reasons that favour the production of multiple queens.

However, of the four reasons above, this paper provides nearly compelling evidence that the workers are selecting which emerge and which do not.

Remember, 53% of the cells that were started were torn down.

In addition, there was both a spatial and temporal bias to the cells that were torn down. This strongly suggests that the process (of cell destruction) was not random.

However, it remains only nearly compelling because we know nothing about the queens that were in cells that were torn down.

By definition those queens don’t exist. The cells were torn down and the queens killed/eaten/discarded so we have no measure of their quality.

If they were indistinguishable from those that did emerge then I’d struggle to convince you that the worker selection was producing ‘better queens’ from the large number of queen cells that were started.

Analysing the non-existent

But fortunately this experiment has been done.

Tarpy, D.R., Simone-Finstrom, M. & Linksvayer, T.A. Honey bee colonies regulate queen reproductive traits by controlling which queens survive to adulthood. Insect. Soc. 63, 169–174 (2016).

The experimental methods were almost identical. However, this time, when they caged the capped queen cells they randomly assigned them to cages that either allowed or prevented worker access (both types of cages prevented the escape of the queen).

They then analysed the queens that emerged from the ‘worker-accessible’ and ‘worker-excluded’ queen cells.

The hypothesis was straightforward, if the workers were randomly destroying a proportion of queen cells there would be no differences in the characteristics of the resulting queens. Conversely, if there was selection, the queens from the ‘worker-excluded’ cells would be different.

The overall numbers of queen cells produced (average 12, range 4 – 22 per colony) and the proportion – 57% – of the ‘worker-accessible’ cells torn down were similar to the study I’ve already described.

Effect of queen treatment on two different measures of queen reproductive potential.

‘Worker-excluded’ queens were significantly smaller than those from ‘worker-accessible’ cages. They also weighed less. This is obvious from the top left panel (above) but confounded 13 by the small size of the study and the significant differences in the weight of queens produced in different colonies 14.

Despite the limited size of this study these results strongly suggest that workers are somehow ‘weeding out’ lower quality (defined here as smaller and probably lighter) queens.

I’ll leave it to you to speculate on how the workers outside the queen cell determine the size/weight/quality of the queen inside the cell … 😉

Does this have relevance to beekeeping?

I think there are a number of interesting points from this study that have relevance to practical beekeeping.

  • Queen cells were started under the emergency response only in the first 3 days after the queen was removed. The vast majority were started within 24 hours. This should help determine when the queen went missing or – if you deliberately removed her – defines the latest date that you need to be concerned about new cells being started.
  • If you are improving your stocks by adding larvae from a separate colony 15 then make sure you add a frame containing eggs and larvae. You want to be sure they have access to 3 day old eggs.
  • It probably makes sense to place this frame in the centre of the brood nest.
  • If you’re grafting larvae for queen rearing – as I’ve already suggested – make sure you choose those under ~18 hours old. The younger and the smaller the better.
  • But, perhaps we should instead think about grafting eggs rather than larvae?

This last suggestion is a topic of a (part-written) future post.

Here are a couple of additional points to think about. Studies have shown that egg transfer results in the largest queens. However, eggs are accepted significantly less well than larvae … and some colonies will not accept them at all. I’ll discuss this in more detail some other time.

And a final caveat …

The final point to remember is that both these studies analysed queen cell production and the resulting queens under the emergency response.

Many queen rearing methods – the so-called ‘queenright’ ones such as my favoured Ben Harden method – exploit the supersedure response. It’s always possible that the bees have different preferences for queens reared under the supersedure (or for that matter the swarming) responses.

But I doubt it 😉

After all … colony survival is dependent upon good quality queens and the bees know best.