Category Archives: Behaviour

Interpretative dance

Synopsis : Interpreting waggle dance distances as indicators of seasonal foraging challenges, environmental change and pollinator competition.

Introduction

The days are getting longer, though not enough to really notice. At almost 57° N we’ve apparently gained ~26 minutes since the winter solstice … but I’ve not seen a bee since early December.

Actually, that’s not entirely true because I checked some colonies this afternoon. As well as hefting the hives to ensure they were still reassuringly heavy I also took a couple of photos from underneath the open mesh floors.

Late December and relatively few corpses on this OMF in the bee shed

Some floors were almost clear, others had a few hundred scattered corpses and there was even the odd bee wandering around.

Why do some floors have more corpses than others?

Remember, the entire worker population of the colony is replaced in the autumn, with the summer foragers gradually dying off and the the long-lived (diutinus) winter bees substituting for them. It’s unlikely that these corpses are summer bee stragglers as they’d be almost three months old by now.

One possibility is that there is a higher attrition rate of winter bees in some colonies (though why is unclear), or the colonies were larger to start with and the same attrition rate yields more corpses. A related explanation would be colonies with the same number of winter bees, though produced at different times. If 1% of bees over, for example, 2 months old died each week ¹, a colony that produced the bulk of its winter bees early would have more corpses than one that produced the winter bees later.

The photobombed picture above is of one of my east coast colonies in the bee shed. Here on the west coast my bees are Varroa-free. The ‘corpse count’ is therefore unlikely to be due to different levels of DWV infection resulting from Varroa infestation. My west coast bees have DWV, but only at very low levels.

It’s also not due to differences in undertaker bee activity as temperatures have been too low for any bees to fly for at least a month.

Anyway, enough morbidity …

The ‘corpse count’ is hardly beekeeping, but it’s as close as I’ll get to do any for at least two months. There are always winter tasks … cleaning smokers, frames, wax processing, honey jarring, painting nucs etc. but enthusiasm levels are low and it’s easier to sit in front of the fire and drink coffee 😉 .

My good deed for the day

To take my mind off corpses and all the frames I’ve yet to start building I’ve been doing some reading about foraging distances and how they vary during the season. This is great because it makes me think of summer days, wildflower meadows, fields of clover and acres of flowering oil seed rape.

By coincidence, this morning there were two articles in The Guardian – on deaths attributable to pollinator decline and severe weather events. It struck me that a better understanding of changes in foraging patterns and activity may be informative in investigating both the decline of pollinators and the consequences of severe weather events like drought.

Front page news … The Guardian 9th January 2023

I’ll return briefly to these two articles at the end, but will concentrate upon how we can determine where the bees are foraging and how this changes during the season.

And, even if you would rather not think about potential ecosystem collapse or climate disaster, from a beekeeping perspective it’s just interesting to know how far our bees are going when they zoom out of the hive entrance on a balmy summer afternoon.

It’s good to talk

Although we can communicate with animals to an extent – I can tell our puppy to ‘sit’ (and she might) – it’s not true communication. Similarly, although we can recognise the differences in songbird alarm calls to sparrowhawks vs. cats, the informational content is extremely limited when compared to true communication.

In contrast, and perhaps uniquely, we can eavesdrop on communication by returning foragers with their nest mates and interpret the distance to the nectar or pollen source, the direction the source is from the hive and – to an extent – the quality of the source (I’m going to restrict discussion to distance and direction here).

All of this information is encapsulated in the waggle dance, for which von Frisch was awarded a Nobel Prize in 1973. Without question this is the most complex communication signal known in insects and, arguably, in any animal.

The waggle dance has two phases; the waggle run is essentially movement in one direction while vibrating the abdomen from side to side, the return phase involves the worker looping back to start another waggle run.

The waggle dance

The informational content of the waggle dance is primarily in the waggle run, the:

duration of the waggle run provides distance information
angle of the waggle run provides directional information, relative to the solar azimuth

By keeping bees in a hive with a glass observation panel and videoing waggle dances we can determine the likely location of nectar or pollen (or tree resins or water under certain conditions) sources after analysing the recordings.

Noisy dancing

However, although it sounds relatively straightforward, dance interpretation is complicated by the inherent noise in the dances of returning foragers.

Foragers returning from a point source of nectar (such as a syrup feeder placed in the field by a scientist) show variation in their waggle dances; both individual foragers in sequential dances, and different foragers reporting the same nectar source.

When decoded this means there is variation in both vector components – distance and direction.

All of which makes accurately monitoring changes in foraging distances over a season or more rather problematic.

However, before describing how scientists have solved this problem think about whether this matters to a bee.

A bit of noise is OK for the bees (right) but just looks like noise to scientists (left)

In nature, although individual locations of nectar ² might be point sources e.g. a flower in a field, in reality the entire field may be filled with similar nectar-yielding flowers. Typically bees rarely have to return to the reported location of a point source.

As long as the dance followers get to the right field they should be OK.

Noise suppression and increasing probability

Using a syrup source to which a colony had been trained, Couvillon and colleagues (Couvillon et al. 2012 ³ ) demonstrated that the first and last waggle runs within any one dance were not very accurate. If these were ignored, but instead four consecutive runs were used from a single dance, this gave much better prediction of the syrup source.

However, this decoded directional and distance information (e.g. 1100 metres at 46°), when plotted onto a map, still just indicates a point source, effectively over-estimating the confidence in the decoded information.

Instead, they reasoned, it would be better to predict a probability distribution.

Roger Schürch did this (Schürch et al., 2013), analysing his own data and published archival data from both von Frisch and Wenner (I introduced you to Adrian Wenner a few months ago when I discussed using Varroa to eradicate honey bees from Santa Cruz Island).

Using some clever ⁴ statistical analysis Schürch showed that; 1) there was a linear relationship between the duration of the waggle run and distance, 2) that angular variation between dances was independent of distance, and 3) that the combination of the two vectors (from several recorded dances and several thousand dances simulated with appropriate levels of scatter in the distance and angle vectors) could be used to plot a probability distribution of the location the bees were reporting during the dance.

Heat map (b) and 3D representation (c) of combined multiple dances

Effectively this method enables a relatively limited dataset to predict the most likely location of the nectar source – in the image above, blue is less likely than yellow, than red.

As you can see from the 3D projection – where probability increases in the vertical axis – it looks pretty good.

Dance like nobody’s watchin’ ⁵

Though there usually is 😉 .

Margaret Couvillon and Roger Schürch worked with Francis Ratnieks at the University of Sussex. Together they applied this methodology to predict the likely foraging areas by conducting waggle dance observations over two full seasons (Couvillon et al., 2014).

They recorded over 5000 dances to track seasonal changes in foraging and so address these questions:

how do foraging areas change over the season?
are foraging distances influenced by temperature?
how might nectar quality influence foraging?

Of course, as soon as you start thinking about questions like these you’ll realise that the observations will inevitably reflect the locally forage available, so the direct results may not be applicable to different areas, but the patterns might be.

And importantly, the methodology may be useful to address other questions in a changing landscape and environment.

4 km circle around the hive location – note urban and rural areas

The hives were located at the University. This was an area surrounded by open farmland ⁶, but Brighton has encroached from the south west. As a consequence at least ~21% of a 4 km circle centred on the University is classed as urban or suburban i.e. built up, but including gardens and allotments etc.

Seasonal variation in foraging distances

From August ’09 until July ’11 (excluding the months between November and March which are too cold for regular foraging) 5076 dances were videoed and analysed. By plotting the average distance reported ⁷ by returning foragers each month, it was clear that bees traveled much further afield in the summer than they did in either the spring or autumn.

Monthly differences in foraging distances

The average distances for early spring (March), summer (July/August) and autumn (September/October ⁸ ) were 493 m, 2156 m and 1275 m respectively.

Temperature and foraging

Although summer is the warmest season, there are warm days in spring and cool days in summer. Since the team recorded dances on almost every day good enough for foraging it was possible to look for a correlation between the actual temperature and the distance reported by dancing foragers.

There wasn’t one.

That means that the longer flights in summer were not because the bees needed a higher ambient temperature to fly further. We can therefore assume that the bees were choosing to fly further, not because they could but because they had to.

Nectar and foraging

Honey bees are able to judge the energetic rewards of a nectar source. This involves a calculation of the energy expended collecting it vs. the energetic ‘value’ of the nectar collected. For example, the bees might favour a distant sugar-rich nectar source over a poorer one that is closer.

It was therefore important to determine whether the increased summer foraging distances were because the bees were favouring nectars with a higher sugar content.

How was this determined?

Returning foragers ⁹ were captured, chilled and gently squeezed to force them to regurgitate the content of their crop. Using a refractometer (of a slightly smaller scale than you might use to measure the water content in a bucket of honey) the sugar content of the crop contents was measured.

About 5% of returning foragers were carrying water, not nectar, and these were excluded when calculating average nectar content.

Whilst there was considerable month to month variation in the sugar content of nectar, there was not a correlation with the foraging distance. Therefore, the bees foraging further afield in the summer weren’t travelling greater distances because the distant nectar sources had a higher sugar content. They were travelling that far because they had to.

The sphere of influence

I used this term previously to describe the area of the landscape potentially impacted by a hive or apiary. Essentially it is defined by the maximum flight distances of the foragers, drones, scouts and queens. Numerically of course, the foragers are the largest group.

Using the methods described above the authors plotted ‘heat maps’ of foraging areas in spring, summer and autumn. The colour scheme is the same as that used above (essentially a probability map of likely foraged areas) – blue is predicted to be the least visited area (though see also the note below), yellow gets more attention and red gets the most.

Heat maps of seasonal differences in foraging – black circles denote 3 and 5 km from hive

There is clearly a big difference in the area visited by foragers in spring (0.8 km²), summer (15.2 km²) and autumn (5.1 km²), and this difference is not because the bees are going further to collect better quality nectars, or because the long hot days of summer encourage them to travel further from the hive.

As an aside … I’d have liked to see this data normalised somehow to forager numbers (which vary over the season) to get a better idea of potential competition for nectar or pollen resources with other pollinators.

It’s worth noting that not all foragers dance, but those that do report the best quality nectar sources. Therefore the maps above, and the distances I discussed even further up the page, represent the best choices the bees have in different parts of the season.

There may be poorer quality nectar sources not mapped by this type of analysis.

Summertime and the livin’ is easy

These studies show that – at least in this particular environment – honey bees have abundant forage close to the hive in early spring. In summer the bees have to forage over an area ~22 times larger ¹⁰ than in early spring to collect the resources they need.

Since the nectar sources are no better the livin’ is anything but easy.

Once the ivy starts flowering (mid/late August in this part of the world) then things get appreciably better and the bees don’t need to travel so far.

There’s no discussion in the paper on the areas foraged, or the potential sources of nectar (other than the ivy), or hive weight changes (which would have been really interesting). However, it seems likely that the large tracts of farmland to the north and east of the hives are very poor in forage during much of the season, and especially in the summer.

The heat maps show that the bees appear to spend more time to the south and the west … both areas where there is the greatest amount of urban development.

Readers with good memories will remember a post explaining the differences in foraging distance between urban and rural bees. The former travelled less far.

Urban environments are often better for bees as there is less boom and bust in terms of available nectar sources.

Generalists

Honey bees are generalists; they can exploit a wide range of nectar and pollen sources. This at least partly accounts for their success and distribution.

Because they are not ‘tied’ to particular flower source(s) they are likely to share many of these sources with other flower-visiting insects, many of which will also be generalists.

It therefore seems likely that the apparent paucity of nectar and pollen sources ‘reported’ by dancing honey bees (who have to travel further to get what they need) will also be experienced by these other pollinators (many of which have smaller home ranges, perhaps 0.25 km² for Bombus terrestris; see Osborne et al., 2001).

Therefore, rather than conducting time consuming survey work recording which flowers are visited by which pollinators (and when), the overall quality and quantity of nectar and pollen in an environment could be determined by monitoring the distances travelled and areas visited by a few honey bee colonies.

Wildflower meadow (in Andalucia)

Are set-aside and land-management programmes optimised to provide nectar and pollen where and when it needed?

Hmmmm.

Competition and environmental change

One reason proposed for the huge decline in non-managed pollinators is from competition with managed honey bee colonies. Honey bees may be generalists and are actually rather inefficient at pollination (in terms of fruit set per visit), but they more than make up for this by sheer weight of numbers.

The studies showing competition is responsible are not completely clear cut, and there are almost certainly other factors that have a greater influence e.g. persistent pesticides, removal of hedgerows and wild flower meadows.

However, if honey bees are struggling to find suitable nectar i.e. having to travel long distances, it’s likely they may be having a landscape-scale impact on other pollinators competing for the same resources in their own (smaller) ranges.

It’s a little sobering to think that our apiaries may be influencing survival and reproduction of other pollinators kilometres away.

Finally, as our climate changes, repeated studies of this type every few years would provide a very good insight into the degradation of the environment.

We know that the gradual warming of the environment is changing the flowering times of plants. We also know that weather extremes – particularly drought – can have a significant impact on seed set which, in turn, will influence the abundance of plants flowering in the following seasons.

Honey bees are the only indicators of these types of qualitative environmental changes that we can directly listen to and understand.

These things are not often discussed by beekeepers … perhaps they should be?

Note to Facebook users/followers

If you are one of the few hundred that rely on Facebook to get announcements of new posts please instead follow me on Instagram or Twitter or even Mastodon (or subscribe for email notifications – right margin). It is likely that the automagic notifications to Facebook will stop in the next few weeks and I don’t use Facebook as I find it a bit ~~overwhelming~~ shambolic 😉

References

Couvillon, M.J., Riddell Pearce, F.C., Harris-Jones, E.L., Kuepfer, A.M., Mackenzie-Smith, S.J., Rozario, L.A., et al. (2012) Intra-dance variation among waggle runs and the design of efficient protocols for honey bee dance decoding. Biology Open 1: 467–472 https://doi.org/10.1242/bio.20121099. Accessed January 10, 2023.

Couvillon, M.J., Schürch, R., and Ratnieks, F.L.W. (2014) Waggle Dance Distances as Integrative Indicators of Seasonal Foraging Challenges. PLOS ONE 9: e93495 https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0093495. Accessed January 7, 2023.

Osborne, J. l., Clark, S. j., Morris, R. j., Williams, I. h., Riley, J. r., Smith, A. d., et al. (1999) A landscape-scale study of bumble bee foraging range and constancy, using harmonic radar. Journal of Applied Ecology 36: 519–533 https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-2664.1999.00428.x. Accessed January 10, 2023.

Schürch, R., Couvillon, M.J., Burns, D.D.R., Tasman, K., Waxman, D., and Ratnieks, F.L.W. (2013) Incorporating variability in honey bee waggle dance decoding improves the mapping of communicated resource locations. J Comp Physiol A 199: 1143–1152 https://doi.org/10.1007/s00359-013-0860-4. Accessed January 9, 2023.

More droning on …

22 Replies

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.

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

8 Replies

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 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

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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 18^th of May when I set up the Morris board. Grafts were added on the 25^th and were capped on the 30^th.

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

On finally checking the bottom box early on the 4^th 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 10^th of June. My notes stated: ’Behaving queenright, but no eggs 🙁 ’.

On the 22^nd 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 29^th, 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 16^th 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 10^th or the 22^nd. 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 24^th 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 2^nd 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 20^th 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

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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:

The statute of limitations has passed 😉
I don’t now and, conveniently, have forgotten the details anyway ¹

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.

Introduction

Why do some floors have more corpses than others?

Anyway, enough morbidity …

It’s good to talk

Noisy dancing

Noise suppression and increasing probability

Dance like nobody’s watchin’ 5

Seasonal variation in foraging distances

Temperature and foraging

Nectar and foraging

The sphere of influence

Summertime and the livin’ is easy

Generalists

Competition and environmental change

Note to Facebook users/followers

References

Introduction

Keeping it topical

Drone eviction

Hannibal the cannibal

The influence of the queen

Egg laying history or drone brood quantification?

But what about the workers?

Comb building

A thousand words

Notes

References

Introduction

Queens

Drones

Workers

Elite foragers

’We have the technology’ 5

Orientation flights and the age of onset of foraging

Workers and shirkers

Lorenz curves

We really do ‘have the technology’

Practice makes perfect

The elite foragers are the best performing foragers

Conclusions and consequences

Looking after the elderly

Deformed wing virus

Unanswered questions

Hive inspections

A gradation of DWV levels

Note

Introduction

It’s all downhill from here

The enjoyment of uncertainty

Weather dependence and queen mating

Pollen

Flying days and mating days

The extremes of the season

Global warming

More misbehaving queens

Pining for the fjords? 7

Like mother, like daughter

And like sister?

Hive records

Introduction

Nice bees

Transient or permanent?

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

Scores on the doors

Compare and contrast

Growing old disgracefully

Aggression

Hive genetics, not individual genetics

Following

Looking for trouble

Running

Spot the queen

Inspections

Better bees

Incremental but steady improvement

Note

Dance like nobody’s watchin’ ⁵

’We have the technology’ ⁵

Pining for the fjords? ⁷