Category Archives: Hives and nucs

Correx: cheap, light, useful. Choose any three

Synopsis : From quick fixes to permanent solutions, Correx – extruded, twinwall, fluted polypropylene – has multiple uses in beekeeping. If you learn how to fold, stick and shape it you can save time, money and space. Here are just a few of the things I use it for.

Introduction

The Spring honey is almost ready to harvest. Supers went from ”filling nicely” to ”Woah! Damn that’s heavy” in the space of a week. They’re now fast approaching ”No more than two at a time” territory which means; a) they’re full, and/or b) I’m less strong than I used to be ¹.

The corpulent supers prompted me to rummage through a teetering stack of equipment to try and find sufficient clearer boards to use before removing the honey supers for extracting.

Clearer boards are effectively one-way ‘valves’ that funnel the bees down into the brood box ².

Quick fix clearer board – hive side

These are two and bit times a season pieces of kit … the Spring and Summer honey harvests and irregular usage to empty the odd brood box when compressing colonies prior to the winter. The rest of the time they sit, unused, unwanted and – not infrequently – in the way.

And, for convenience, you need more than one.

I like to have one for every hive in the apiary, particularly when taking the summer honey off. That way you can strip all the hives simultaneously, so avoiding problems with robbing. None of my apiaries are particularly big, but it still means I’ve needed up to a dozen clearer boards at a time.

That’s a lot of wood and limited-use kit to sit around unused. I therefore build lots of them from Correx.

Clearer boards – one wood and six made from ekes and Correx

This post isn’t about clearer boards. I’ve described those before.

Instead it’s about Correx and the myriad of uses that it can be put to.

If you don’t use it you’re probably missing out.

If you do, you probably have some additional uses to add to the list below.

Correx

Correx is a registered trademark owned by DS Smith. Other trademarks (by other companies) include Cartonplast, Polyflute, Coroplast, FlutePlast, IntePro, Proplex, Twinplast, Corriflute or Corflute … and there are probably some I’ve missed.

It’s all very similar stuff, variously described as corrugated plastic or corriboard, and perhaps more accurately described as an extruded, twinwall, fluted polypropylene.

If you don’t know what I’m talking about then you’re probably familiar with the material they make For Sale signs from … that’s Correx ³.

For sale …

Correx is lightweight, impervious to most oils, solvents and water, relatively UV resistant and recyclable. These characteristics make Correx ideal for a range of beekeeping applications.

It is easy to cut and can be folded, with or across the ‘grain’ if you know the tricks of the trade.

Correx is available in a range of thicknesses – typically 1-8 mm. Two millimetre Correx is often used as a protective floor covering in new buildings. However, it’s rather thin and flimsy.

Almost everything I use is 4 mm and so, unless I state otherwise, assume that’s what I’m referring to in the text below.

Almost certainly the stuff I use is not Correx, but I’ll call it Correx for convenience ⁴.

Before discussing ⁵ applications I’ll make a few comments on sourcing Correx and cutting, gluing and folding it.

Free Correx

For Sale signs belong to the estate agent selling the house. However, they’re often not collected after the house sale completes and are dumped in a nearby ditch, stuffed down the side of the garage or otherwise discarded. Many still have the 2.4 m wooden post attached.

If they really are unwanted it’s often a case of ’ask and ye shall receive’ … and, if the sign is in a ditch, you don’t probably even need to ask.

When I lived in a semi-urban area I used to carry a handsaw in the car to help my repurposing of these sorts of signs.

Elections are another good source, particularly if the candidate in your ward a) loses ignominiously, and b) immediately retires. It’s unlikely the political party will find another Archibald Tristan Cholmondeley-Warner to stand for them, so the electioneering signs are – like the politician – surplus to requirements.

As always, never walk past a part-filled skip without having a good look at the contents 😉

Never!

Buying Correx

Correx is relatively inexpensive when bought in multiples of 2.4 x 1.2 metre sheets ⁶. I’ve paid about £10 a sheet delivered for 5 or more, purchased from eBay, but can’t find anything quite that price when I had a quick look this week.

You might not think you need 14 square metres of Correx but you’d be surprised at the things it can be used for. It’s also easy to store behind a bookcase or in the shed.

Correx sheet …

It’s also worth asking at local plastics and printing companies that may have offcuts or failed print runs. It doesn’t matter what’s printed on the Correx ⁷. There’s a beekeeper in Northern Ireland that crafted a nuc box out of election propaganda bearing a photo of the candidate. The nuc entrance was arranged to be the politicians mouth.

Be creative.

Finally, Correx is often used to make guinea pig cages or runs, so befriend a cavie-keeper and you might locate the mother lode ⁸ 😉

Correx engineering

Thin Correx (4 mm) is easy to work with. It can be cut with a Stanley knife. All you need is a good straightedge, a steady hand ⁹ and a sharp blade. Marking up the sheets is easiest in pencil as many pens don’t work on the smooth impervious surface ¹⁰. Pencil works equally well on black or white sheets.

I’d recommend you don’t use scissors as they tend to crush the sheet. It’s also difficult to cut large sheets with a small pair of scissors.

Folding Correx

Correx has a ‘grain’ created by the vertical internal ribs that connect the upper and lower faces of the sheet. If you need to fold the sheet you’re working with, the method used depends whether you are folding across or with the grain.

To fold across the grain you need to crush the ribs without cutting through the upper face of the sheet. To achieve this use a pizza cutter and a straightedge. A pizza cutter is usually sufficiently blunt that the sheet isn’t cut. The crushed side of the sheet becomes the inner angle of the fold.

Pizza cutter … take care scoring the Correx

Making folded corners requires a little ingenuity but is obvious once you realise how the sheet folds ¹¹.

Corner detail …

To fold with the grain requires a small amount of surgery. First cut on either side of a rib, then fold the sides back leaving a T-shaped piece – formed by the rib and a small piece of the upper face of the sheet – protruding. Then, with a steady hand and a sharp knife, cut the leg of the T away.

Folding Correx with the grain – cut one of the ribs away

The sheet then folds easily with the uncut face forming the outer angle of the corner.

Gluing Correx

This is tricky. I’ve tried every glue in my workshop and none of them work. The surface of Correx has some sort of treatment that means that glues do not adhere. There are tricks that involve flaming the surface to remove the treatment, but – at least in my experience – they are hit and miss.

Usually miss 🙁

There are commercial hotmelt adhesives ¹² that can be used – like the ones the estate agents use to stick two signs back-to-back – but they are quite expensive.

Whatever the surface treatment is, it also prevents many sticky tapes adhering properly or permanently.

But there’s one exception … Unibond Power Tape Plus. It’s available in silver and black. Critically for beekeeping it’s both waterproof and temperature resistant. This tape is about a fiver a roll and this represents excellent value for money.

Sticky stuff …

I’ve got some Correx hive roofs held together with Unibond Power Tape that have been in constant use since 2014, outdoors (obviously) in temperatures ranging from sub-zero to 30°C or more ¹³.

Highly recommended.

To help the tape stick even better it’s worth gently abrading the surfaces to be taped together using wet and dry sandpaper and then cleaning with a solvent like acetone. Press the tape down firmly and check it in about a decade or so.

Uses

I’m going to concentrate on the uses I make of Correx, because those are the things I have experience of.

There are lots of other things you could use it for … for example, I’ve not built nuc boxes from Correx, but I know you can. They are increasingly used by the bulk commercial nuc suppliers. If you don’t want to build your own you can purchase these boxes for £9 to £12 each ¹⁴, flat-packed, in National or Langstroth formats. These boxes tend to use interlocking tabs to hold them together, rather than tape or glue. They might be suitable for short term, summer usage, but not for overwintering a nuc colony.

Roofs

I’ve made lots of Correx roofs and they are still in everyday use, either on hives or on stacks of spare boxes. I’ve described how to build them in detail, together with their pros and cons.

Correx in the frost …

Everything I wrote 7 years ago is still valid, so I won’t repeat it here.

A single 2.4 x 1.2 sheet of Correx is big enough to produce 8 roofs. Even if you can’t find Correx cheaper than £13 a sheet that’s still less than £1.75 a roof including the cost of the tape holding it together ¹⁵.

I routinely successfully overwinter colonies with Correx roofs covering a 50 mm thick block of Kingspan insulation.

Semi-permanent division boards e.g for vertical splits

In my experience these are one of the few things ¹⁶ that cannot be satisfactorily made from 4 mm Correx.

These types of boards might be separating brood boxes for a month or more while one half of a vertical split requeens. During this time the board tends to warp. The bee space increases on one side and is destroyed on the other. Consequently the bees build unwanted brace comb above and below the frames.

Correx split board …

I now only use my 4 mm Correx split boards in extremis. I know that some of the commercial beekeepers use 6 mm or 8 mm Correx split boards. The additional rigidity of the thicker Correx presumably withstands warping sufficiently.

If When I run out of equipment I’ve been known to use split boards as crownboards. For the same reasons – warping – I try and avoid using horizontal sheets of Correx in the hive for extended periods.

Temporary division boards e.g. Cloake and clearer boards

In contrast, Correx is ideal when used for limited periods in the hive. One obvious application is the removable slide in a Cloake board for queen rearing.

Cloake board …

Mine was built from a For Sale sign rescued from a skip in Newcastle. It’s one of the thicker pieces of Correx I’ve used (6 or 8 mm) and is significantly more rigid than the standard 4 mm sheets. However, I’m sure that 4 mm would do as the slide is only in place for about 24 hours to induce the emergency response and initiate queen cell production.

As I wrote in the introduction, the majority of my clearer boards are built from Correx. I now zip tie the escapes to the underside of the board ¹⁷ and then pair them with a simple eke when I need to use them for clearing supers.

Zip tied escape on a Correx clearer board

These work fast and efficiently, they don’t warp and they can be separated from the eke and stored separately (where they take up little space) if/when the eke is being used for something else (like a spacer to provide an upper entrance, or whilst vaporising from above the brood box).

Floors

The only floors I’ve built with Correx are those for bait hives when paired with two stacked supers. These work really well.

Bait hive floor

Bait hives should have solid floors, so if I want to use an open mesh floor on a bait hive I simply lay a small sheet of Correx on the mesh and remove it once the hive is occupied.

Varroa trays

Most, or at least many, commercial Varroa trays are made of Correx ¹⁸. To make counting mites easier it helps to draw a grid on the tray.

Varroa tray gridded to make counting mite drop easier

Of course, to make counting mites really easy it helps if there are few of them. Use miticides properly and at the right time. In that way your Varroa levels will never get too high and you’ll never run out of fingers when counting the mite drop 😉

OK, perhaps a slight exaggeration, but it’s certainly easier to count low numbers of mites rather than thousands. I’ve seen post-treatment mite drops so heavy you could trace patterns through the mite corpses with your finger, and the easiest way to count them was with a digital lab balance.

Ewww!

Landing boards

Almost all of my hives have Correx landing boards. Some are integral to the kewl floors I use …

Correx kewl floor landing board

… while others are attached to the outside of my bee shed.

Laden foragers returning …

You can paint Correx with a variety of different types of paint. Radiator enamel or car spray paint works well. Using different colours and/or decorating the landing board with distinctive shapes helps bees orientate to the hive entrance and reduces drifting.

For vertical surfaces, try sprinkling sand onto the semi-dry paint before over-spraying to provide laden foragers better grip when entering the hive.

My white Correx landing boards are starting to exhibit UV damage after 4-5 years of use. Either avoid white, paint them or put up with having to infrequently (and inexpensively) replace them.

Miscellaneous

Most of my nucs are red ¹⁹ or blue. When I’m making up lots of nucs for queen mating I pin Correx shapes above the entrance to help the bees – and particularly the queens – distinguish between the hives. Again this reduces problems with drifting.

Correx signage on poly nucs

Almost all my nuc boxes are Thorne’s Everynucs. These are well designed except for the cavernous entrance. Again, Correx can be used to fix the situation; I use it to block the entrance entirely for travel, or to provide a much reduced entrance that is easier for the small colony to defend.

Correx, the beekeepers friend …

I’m currently busy rearing my first queens of the season. The method I’m using involves sealing the standard hive entrance and redirecting the bees to an upper entrance ²⁰. This process is really speeded up by leaning a sheet of Correx against the front of the hive, directing the returning foragers to the upper entrance.

Correx sheet redirecting returning foragers

Doing this stops the bees milling around the original entrance and is particularly helpful in borderline weather conditions e.g. low temperatures and intermittent showers ²¹, when it prevents bees getting chilled.

Correx and tape were used to build these ‘fat dummies’

Fat dummies for queen rearing? Correx to the rescue.

I could go on … but I won’t.

You’ve got the general idea by now.

If you’ve found additional uses for Correx then please add a comment below.

Cut more losses

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This is a follow-on to the post last week, this time focusing on feeding and a few ‘odds and sods’ that failed to make it into the first 3000 words on reducing overwintering colony losses.

Both posts should be read in conjunction with one (or more ¹ ) of my earlier posts on disease management for winter. Primarily this involves hammering down the mite levels before the winter bees are produced, so ensuring their longevity.

But also don’t forget to treat your colonies during a broodless period in midwinter to mop up mites that survived the autumn treatment, or have reproduced since then.

Why feed colonies?

All colonies need sufficient stores to get the colony through the winter until suitable nectar sources and good enough weather make foraging profitable the following spring.

How much the colony needs depends upon the bees themselves – some strains are more frugal than others – and the duration of the winter. If there is no forage available, or the weather is too poor for the bees to fly, then they will be dependent upon stores in the hive.

A reasonable estimate would probably be somewhere around 20 kg of stores, but this isn’t a precise science.

It’s better for the colony to have too much than too little.

If the colony has stores left over at winter’s end you can always remove them and use them when you make up nucs later in the season. Just pull out the frames and store them safely until needed.

Unused winter stores

In contrast, if the colony starts the winter with too few stores there are only two possible outcomes:

the colony will starve to death, usually in late winter/early spring (see below)
you will spend your winter having to regularly check the colony weight and opening the hive to add “emergency rations” to get them through the winter

Neither of these is desirable, though you should expect to have to check the colony periodically in winter anyway.

Feeding honey for the winter … and meaningless anecdotes

By the end of the summer the queen has reduced her laying rate and the bees should be backfilling brood comb with honey stores. If you assume there’s about 5 kg of stores ² in the brood box then they’ll need about another 15 kg.

15 kg is about the amount of honey you can extract from a well-filled super.

Convenient 😉

Some beekeepers leave a full super of honey on the hive, claiming the “it’s better for the bees than syrup”.

Of course, it’s a free world, but there are two things wrong with doing this:

where is the evidence that demonstrates that honey is better than sugar-based stores?
it’s an eye-wateringly expensive way to feed your colonies

By evidence, I mean statistically-valid studies that show improved overwintering on honey rather than sugar.

Not ‘my hive with a honey super was strong in spring but I heard that Fred lost his colony that was fed syrup’ ³.

That’s not evidence, that’s anecdote.

If you want to get this sort of evidence you’d need to start with a lot of hives, all headed by queens of a similar age and provenance, all with balanced numbers of brood frames/strength, all with similar mite levels and other pathogens.

For starters I’d suggest 200 hives; feed 50% with honey, 50% with sugar … and then repeat the study for the two following winters.

Then do the stats ⁴.

The economics of feeding honey

If I were a rich man …

The 300 supers of honey used for that experiment would contain honey valued at about £80,000.

That’s profit, not sale price (though it doesn’t include labour costs as I – and many amateur beekeepers – work for free).

The honey in a single full super has a value of £250-275 … that’s an expensive way to feed your bees ⁵.

Particularly when it’s not demonstrably better than a tenner or so of granulated sugar 🙁

But there are more costs to consider

The economic arguments made above are simplistic in the extreme. However, there are other costs to consider when feeding colonies.

time taken to prepare and store whatever you will be feeding them with ⁶
feeders needed to dispense the food (and storage of these when not in use)
energetic costs for the colony in converting the food to stores

Years ago I stopped worrying (or even thinking much) about any of this and settled on feeding colonies fondant in the autumn.

Fondant mountain …

Fondant is ~78% sugar, so a 12.5 kg block contains about 9.75 kg of sugar.

This year I’m paying £11.75 for fondant which equates to ~£1.20 / kg for the sugar it contains.

In contrast, granulated sugar is currently about £0.63 / kg at Tesco.

The benefits of fondant

Although my sugar costs are about double this is a relatively small price I’m (more than) prepared to accept when you take into account the additional benefits.

zero preparation time and no container costs. Fondant comes ready-wrapped and stores for years in the box it is purchased in
no need for jerry cans, plastic buckets or anything to prepare or store it in before use
no need for expensive Ashforth-type feeders that sit around for 95% of the year unused When I last checked an Ashforth feeder cost £66 😯
it takes less than 2 minutes to add fondant to a colony
no risk of spillages – in the kitchen, the car or the apiary ⁷.
fondant is taken down more slowly than syrup, so providing more space for the queen to continue laying. In addition, in the event of an early cold snap, fondant remains accessible whereas bees often stop taking syrup down

Regarding the energetic costs for the colony in storing fondant rather than syrup … I assume this is the case based upon the similarity of the water content of fondant to capped stores (22% vs. 18%), whereas syrup contains much more water and so needs to be ripened before capping to avoid fermentation.

Fondant block under inverted perspex crownboard – insulation to be added on top.

Whether this is correct or not ⁸, the colony has no problem taking down the fondant over a 2-4 week period and storing it.

What are the disadvantages of using fondant?

The only one I’m really aware of is that the colony will not draw fresh comb when feeding on fondant (or at least, not enthusiastically). In contrast, bees fed syrup in the autumn and provided with fresh foundation will draw lovely worker brood comb.

Do not underestimate this benefit.

They fancied that fondant

Brood frames of drawn comb are a very valuable resource. Every time you make up a nuc, or shift a nuc to a full-sized box, providing drawn comb significantly speeds up the expansion of the resulting colony.

Nevertheless, for me, the advantages of fondant far outweigh the disadvantages …

Finally, in closing, I’ve not purchased or used invert syrup for feeding colonies. Other than no prep time this has the same drawbacks as syrup made from granulated sugar. Having learnt to use fondant a decade or so ago from Peter Edwards (Stratford BKA) I’ve never felt the need to look at other options.

Let’s move on …

Ventilation and insulation

Bees can withstand very cold temperatures if healthy and provided with sufficient stores. In northern Canada bees may experience only 120 frost-free days a year, and cope with 3-4 week periods in winter when the temperature is -25°C (and colder if you consider the wind chill).

That makes anywhere in the UK look positively balmy.

Margate vs. the Maldives … a similar temperature difference to Margate vs. Manitoba in the winter

I’ve overwintered colonies in cedar or poly boxes for a decade and not noticed a difference in survival rates. Like the honey vs. sugar argument above, if there is a difference it is probably minor.

However, colony expansion in poly boxes in the spring is usually better in my experience, and they often fill the outer frames with brood well before cedar boxes in the same apiary get there.

Whether cedar or poly I take care with three aspects of their insulation/ventilation:

the colonies have open mesh floors and the Varroa tray is only in place when I’m actively monitoring mite drop
all have insulation above the crownboard in the form of a 50 mm thick block of Kingspan (or Recticel, or Celotex), either integrated into the crownboard itself, placed above it or built into the roof
I ensure there is no upper ventilation – no matchsticks under the crownboard, no holes etc.
excess empty space in the brood box is reduced to minimise the dead air space the bees might lose heat to

In my experience bees actively dislike ventilation in the crownboard. They fill mesh with propolis …

Exhibit A … are you getting the message?

… and block up the holes in those over-engineered Abelo crownboards …

Exhibit B … ventilated hole in an Abelo crownboard

Take notice of what the bees are telling you … 😉

Insulation over the colony

I’ve described my insulated perspex crownboards before. They work well and – when inverted – can just about accomodate a flattened ⁹, halved block of fondant.

Perspex crownboard with integrated insulation

Finally, if it’s a small colony in a brood box ¹⁰ then I reduce the dead space in the brood box using a fat dummy.

Fat dummy …

I build these filled with polystyrene chips.

You don’t need this sort of high-tech solution … some polystyrene wrapped tightly in a thick plastic bag and sealed up with gaffer tape works just as well.

Insulation …

I’ve even used bubblewrap or that air-filled plastic packaging to fill the space around a top up block of fondant in a super ‘eke’ before now.

However, remember that a small weak colony in autumn is unlikely to overwinter as well as a strong colony. Why is it weak? Would you be better uniting it before winter starts?

Nucleus colonies

Everything written above applies equally well to nucleus colonies.

A strong, healthy nuc should overwinter well and be ready in the spring for sale or promoting to a full colony.

Here’s one I prepared earlier … an overcrowded overwintered nuc in April

Although I have overwintered nucs in cedar boxes I now almost exclusively use polystyrene. This is another economic decision … a well made cedar nuc costs about double the price of the best poly nucs.

I feed my nucs fondant in preparation for the winter, typically by adding 1-2 kg blocks to the integral feeder.

Everynuc fondant topup

Because of the absence of storage space in the nuc brood box it’s not unusual to have to supplement this several times during the autumn and winter.

You can even overwinter queens in mini-mating nucs like Apidea’s and Kieler’s.

Kieler mini-nuc with overwintering queen

This deserves a post of its own. Briefly, the mini-nuc needs to be very strong and usually double- or triple- height. I build fondant frame feeders for Kieler’s that can be quickly swapped in/out to compensate for the limited amounts of stores present in the brood box.

Kieler mini-nuc frame feeders

My greatest success in overwintering these was in winters when I provided additional shelter by placing the nucs in an unheated greenhouse. A tunnel provided access to the outside. However, I know several beekeepers who overwinter them without this sort of additional protection (and have done so myself).

Just because this can be done doesn’t mean it’s the best thing to do.

I’d always prefer to overwinter a colony as a 5 frame nuc. The survival rates are much better, their resilience to long periods of adverse weather is significantly greater, and they are generally much more useful in the spring.

Miscellaneous musings

Hive weight

A colony starting the winter with ample stores can still starve if the bees are particularly extravagant, or if they rear lots of brood but cannot forage.

The rate at which stores are used is slow late in the year and speeds up once brood rearing starts again in earnest early the following spring (though actually in late winter).

Colony weight in early spring

As should be obvious, this is a Craptastic™ sketch simply to illustrate a point 😉

The inflection point might be mid-December or even early February.

The important message is that, once brood rearing starts, consumption of stores increases. Keep checking the colony weight overwinter and supplement with fondant as needed.

I’m going to return to overwinter colony weights sometime this winter as I’m dabbling with a weather station and set of hive scales … watch this space.

An empty super cuts down draughts

Periodically it’s suggested that an empty super under the (open mesh) floor of the hive ‘cuts down draughts’, and is therefore beneficial for the colony.

It might be.

But like the ‘overwintering on honey’ (and being a ~~pedant~~ scientist) I’d always want to see the evidence.

There are two claims being made here:

a super under the floor cuts down draughts
fewer draughts benefits the colony which consequently overwinters better

Really?

There are ways to measure draughts but has anyone ever done so? Remember, the key point is that the airflow around the winter cluster would be reduced if there are fewer draughts.

Does a super reduce this airflow significantly over and above that already caused by the sidewalls of the floor?

And, even if it does, perhaps the colony ‘reshapes’ itself to accommodate the draught from an open mesh floor.

What shape is the winter cluster?

For example, in an uninsulated hive (including no insulation over the cluster) with a solid floor the cluster is likely to be roughly spherical. They minimise the surface area.

With an open mesh floor are they more ellipsoid, so avoiding draughts from below? If so, is this improved much by an empty super below the open mesh floor? Does the cluster change shape or position? I don’t know as I’ve not compared cluster shapes in solid vs. open mesh floors plus/minus a super underneath.

And anyway, an open mesh floor looks very like a baffle to me … how much better can it get? How draughty is it in the first place?

Is this example 8,639 for my ‘Beekeeping Myths’ book?

I do know that top insulation tends to flatten the cluster against the warm underside of the crownboard.

A strong colony in midwinter

Having worked out that draughts are (or are not) reduced … you still need another couple of hundred hives to test whether overwintering success rates are improved!

More winter bees

Finally, always remember that the survival of the colony is dependent upon the winter bees. All other things being equal (stores, disease etc.), a colony with lots of winter bees will overwinter better than one with fewer.

This is one of the reasons I stopped using Apiguard for mite control in autumn. Apiguard contains thymol and quite regularly (30-50% of the time in my experience) stopped the queen from laying, particularly in warmer weather.

Apiguard works well for mite control, but I became wary that I was potentially stopping the queen at a time critical for late-season colony development. I worried that, once treatment was finished, a cold snap would shut down brood rearing leaving it with suboptimal numbers of winter bees.

I never checked to see whether the queen ‘made good’ any shortfall after removal of the treatment … instead I moved to Scotland where it’s too cold to use Apiguard effectively 🙁

Supering

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Something short and sweet this week ¹ … though perhaps ‘tall and sweet’ would be preferable as I’m going to discuss supering.

The noun supering means ‘the action or practice of fitting a super to a beehive’ and dates back to 1840:

Duncan, James. Natural History of Bees Naturalist’s Library VoI. 223 The empty story which is added, may be placed above, instead of below the original stock, and the honey will thus be of a superior kind. This mode of operating is called super-ing, in contra-distinction to nadir-ing.

I don’t quite understand the description provided by here. Adding a super underneath the colony (original stock) is unlikely to lead to it being used as a honey store. Bees naturally store honey to the side and above the brood nest.

And does James Duncan mean the honey is superior because it’s better? Or is he using superior in its zoological sense meaning ‘at or near the highest point’? ²

So … let’s get a few definitions out of the way first.

Supering – the addition of a super to a hive, which could be either:
- Top-supering – adding a super to the top of a stack of existing supers, or
- Bottom-supering – adding a super below any existing supers, but above the brood box(es)
Nadiring – the addition of a super below an existing brood box (which won’t be mentioned again in this post ³.

Supering … click for legend

I prefer the term top- or bottom-supering as the alternative over- or under-supering could be misinterpreted as the amount of supers being excessive or insufficient.

Which is better – top- or bottom-supering?

Let’s get the science out of the way first.

There’s an assumption that bottom supering should be ‘better’ (in terms of honey yield) as it reduces the distance bees have to travel before they are relieved of their nectar.

A study conducted two decades ago by Jennifer Berry and Keith Delaplane ⁴ showed that – in terms of the amount of honey stored – it makes no statistical difference whether top- or bottom-supering is used.

This study was conducted at the University of Georgia (USA). It used 60 hives – 3 different apiaries each containing 10 hives over two distinct nectar flows.

Note the deliberate inclusion of the term ‘statistical’ above … the bottom-supered hives did end up with ~10% more honey in total but, considering the scale of the experiment, this was not statistically significant.

To determine if this difference was real you’d need to do a much larger scale experiment.

This was not simply weighing a few hives with the supers added on top or below … each colony used was balanced in terms of frames of brood, numbers of bees and levels of stores in the brood box for each nectar flow. That’s not my idea of fun when it would involve a few thousand colonies 🙁 ⁵.

The Berry & Delaplane study reached the same conclusion as earlier research by Szabo and Sporns (1994) who were working in Alberta, Canada ⁶. They had concluded that the failure to see a significant difference in terms of honey stored was because the nectar flows were rather poor. However, this seems unlikely as the Berry & Delaplane study covered two nectar flows, one of which was much stronger than the other (measured in terms of honey yield).

Before we leave the science there’s a minor additional detail to discuss about the Berry & Delaplane study. All their hives consisted of a single Langstroth brood box with a honey super on top underneath the queen excluder (refer to C. in the figure above).

This first honey super was termed the ‘food super’. The remaining supers were the ‘honey supers’. It’s not clear from the description in the paper whether the queen ever moved up to lay in the ‘food super’. I’m assuming she did not.

That being the case, the bottom supering employed by Berry & Delaplane is probably not quite the same as understood by most UK beekeepers.

When I talk about bottom-supering (here and elsewhere) I mean adding the super directly above the box that the queen is laying in (refer to A. in the figure above).

Whether ‘true’ bottom-supering leads to increased honey yields I’ll leave to someone much stronger than me. It’s an experiment that will involve a lot of lifting … and a lot of hives 😉

Which brings us to other benefits associated with where the super is added …

Benefits of bottom supering

I can think of two obvious ones.

The first is that the frames are immediately above the warmth of the broodnest. This might help get new foundation drawn a bit faster. However, if the flow is so good you’re piling the supers on it’s likely that the bees will draw comb for fun.

Note also the comments below about frame spacing and brace comb. I start new supers with 11 frames and subsequently reduce the number to 9. To avoid brace comb it’s easier to get undrawn supers built when there are no other supers on the hive. However, if that’s not possible I usually bottom-super them … it can’t do any harm.

The second benefit is that by bottom-supering the cappings on the lowest supers always stay pristine and white. This is important if you’re preparing cut comb honey. It’s surprising how stained the cappings get with the passage of hundreds of thousands of little feet as the foragers move up to unload their cargo in top-supered colonies.

Benefits of top supering

Generally I think these outweigh those of bottom-supering (but I don’t make cut comb honey and I’d expect the sale price of cut comb with bright white cappings trumps any of the benefits discussed below).

The first is that it’s a whole lot easier on your back 🙂

No need to remove the stack of supers first to slide another in at the bottom. This is a significant benefit … if the colony needs a fourth super there’s probably the best part of 50 kg of full/filling supers to remove first ⁷.

Lifting lots of heavy supers is hard work. A decade ago I’d tackle three full supers at a time without an issue.

More recently, honey seems to be getting much denser 😉 … three full supers, particularly if on top of a double brood box, are usually split into two (or even three) for lifting.

Secondly, because top-supering is easier it’s therefore much quicker.

Pop the crownboard off, add another super, close up and move on.

Some claim an additional benefit is that you can determine whether the colony needs an additional super simply by lifting off the crownboard and having a peek. That might work with a single brood box and one super ⁸, but it’s not possible on a double brood monster hive already topped with four supers ⁹.

Of course, all of the benefits in terms of ease of addition and/or lack of lifting are null and void if you are going to be inspecting the colony and therefore removing the supers anyway.

Frame spacing in supers

Assuming a standard bee space between drawn, filled, capped honey stores, the more frames you have in the super the smaller the amount of honey the super will contain.

This might never be an issue for many beekeepers.

However, those that scale up to perhaps half a dozen hives soon realise that more frames per super means more time spent extracting.

That’s exactly what happened with me. My epiphany came when faced with about 18 supers containing almost 200 frames and a manual (hand cranked) three-frame extractor 🙁

By the next nectar flow I’d invested in an electric 9 frame radial extractor and started spacing my frames further apart.

That first ‘semi-automated’ honey harvest paid for the extractor and my physique became (just) slightly less Charles Atlas-like.

With undrawn foundation I start with a full box of 11 frames. However, once drawn I space the frames further apart, usually 9 per super. The bees draw out deeper comb and fill it perfectly happily … and I’ve got less frames to extract 🙂

I know some beekeepers use 8 frames in their supers. I struggle with this and usually find the bees draw brace comb or very uneven frames. This might be because our nectar flows aren’t strong enough, but I suspect I’ve spaced the frames too far apart in one go, rather than doing it gradually.

Frame alignment of supers

Speaking of brace comb … remember to observe the correct bee space in the supers. Adding a super with mismatched frame numbers will result in brace comb being built at the junction. The same thing happens if frames are misaligned.

Frame spacing and alignment in the supers.

Inevitably this brace comb ends up fusing the two supers together and causes a ‘right mess’ ¹⁰ when you eventually prize them apart.

And you’ll have to because they’re probably too heavy to lift together.

Brace comb …

The example above is particularly bad due to the use of misaligned foundationless super frames. The comb is, as always, beautiful … and unusually in this example the bees built from the bottom upwards.

Note that the frame alignment between adjacent boxes does not appear to apply to the brood box and the first super. At least, it doesn’t when you’re using a queen excluder. I presume this is because the queen excluder acts as a sort of ‘false floor’. It disrupts the vertical bee space sufficiently that the bees don’t feel the need to build lots of brace comb.

You can use castellations to space the frames in the supers. I don’t (and got rid of my stock of used and unused castellations recently) as they prevent re-spacing the frames as needed ¹¹. The bees quickly propolise up the frame lugs meaning the frames are effectively immovable without the application of significant force.

Oops …

Like with a hive tool … or if you drop the super 🙁 ¹².

Caring for out of use supers

After drawn brood comb, drawn supers are probably the most valuable resource a beekeeper has.

You can’t buy replacement so it makes sense to look after it.

Of course, having written the sentence above I realised I was almost certainly wrong. A quick Google search turned up this Bad Beekeeping post from Ron Miksha who described commercially (machine) produced drawn comb.

Three Langstroth-sized combs are €26 😯

There’s also this stuff …

OK, so I stand corrected. You can buy replacement drawn comb, but a single super will cost you about €78 ¹³ so they should be looked after.

Empty drawn supers should be stored somewhere bee, wasp and rodent-free. I store mine in a shed with a solid floor underneath the stack and a spare roof on top.

Late November in the bee (storage) shed …

I have friends who wrap their supers in clingfilm … not 30 cm kitchen roll, but the metre wide stuff they use in airports to wrap suitcases ¹⁴.

Wax moth infestation of drawn supers is generally not a problem. They much prefer used brood frames. However, it makes sense to try and make the stacks as insect-proof as possible.

Caring for in use supers

If the supers are full of bees and honey then the drawn comb is only the third most important thing in the box.

Don’t just pile the supers on the ground next to the hive. The lower edges of the frames will be festooned with bees which will get crushed. You’ll also pick up dirt from the ground which will then be transferred to the hive.

Instead, use an inverted roof. Stand the super(s) on it, angled so they’re supported just by the edges of the roof. This minimises the opportunities for bees to get squashed.

If you’re removing a stack of supers individually (because they’re too heavy to lift together) do not stack them up in a neat pile as you’re very likely to crush bees. It’s better to support the super on one edge, propped up against the edge/corner of the first super I removed.

Again, this minimises the chances of crushing bees. It’s distressing for the beekeeper, it’s definitely distressing for the bee(s) and it’s a potential route for disease transmission.

The multi-purpose Correx hive roof

Once the supers are emptied of bees but full of capped honey you’ll need to transport them home from the apiary. I use spare Correx hive roofs to catch the inevitable drips that another more caring member of the household would otherwise discover 🙁

These Correx hive roofs aren’t strong enough to stack supers on. I always ensure there’s at least one or two conventional roofs in each apiary to act as temporary super stands during inspections.

Final thoughts

Tidy comb

At the end of the season it’s worth tidying the super frames before stacking them away for the year.

Super frames before tidying and storage

I use a hive tool to scrape off any bits of brace comb from the top and bottom bars of each frame. I also use a breadknife to level up the face of the comb. The combs are then arranged in boxes of nine and stored away for the winter.

A small amount of time invested on the supers saves time and effort doing much the same thing when you need them.

Drone foundation in supers

Over 50% of my supers are drawn from drone foundation.

There are two advantages to using drone foundation in the supers. The first is that there’s less wax and more honey; it takes less effort for the bees to build the comb in the first place and the larger cell volume stores more honey.

In addition, with less surface area in each cell, it’s at least theoretically possible to get a greater efficiency of extraction ¹⁵.

The second benefit is that bees do not store pollen in drone comb. In a strong colony you sometimes get an arch of pollen stored in the bottom super, and this is avoided by using drone comb.

Drone comb in super

That doesn’t mean that they’ll necessarily fill the comb with nectar. Quite often they just leave an empty arch of cells above the brood nest 🙁

The major problem with using drone comb in the supers occurs when the queen gets above the queen excluder. You end up with my million drones fiasco and a lot of comb to melt down and recycle.

The super frame shuffle

Bees often draw and fill the central frames in the super before those at the sides. This can lead to very unevenly drawn comb (which can be ‘fixed’ with a breadknife as described above), and grossly unbalanced comb when extracting.

Full super ready for extraction …

To avoid this simply shuffle the outer frames into the centre of the super and vice versa. The frames will be much more evenly filled.

Spares

If you have an out apiary, keep spare supers in an insect-proof stack in the apiary.

Spare supers … only one now, on hive #29

Alternatively, keep spares under the roof but over the crownboard. As a strong nectar flow tails off, or if the weather is changeable, it might save a trip back to base, or having to carry yet another thing on your rounds.

Note

I’ve now done the calculation … 11 National super frames have an area of ~5500 cm² which would require 6.5 Langstroth-sized sheets of drawn commercial comb. At the prices quoted above (€26 for three) that would only cost about €56 … but you’d still have to slice’n’dice them into the frames.

Hmmm … almost 3000 words … not so short and sweet after all 🙁

In the bleak midwinter

Winter has finally arrived.

Green thoughts in a white shade

We’ve had temperatures fluctuating around 0°C for the last two to three weeks now, with some very hard frosts and more than enough snow to make the track impassable.

Like the bees, I’ve spent the time hunkered down focusing on keeping warm and conserving my stores.

Unlike my bees, I’ve benefited from triple glazing and a wood burning stove 😉

And the main thing I’m worried about running out of is milk for my cappuccino ¹.

The 20^th was particularly cold with temperatures well below -5°C and stunningly clear. There was something strange about the conditions, as the loch froze. The surface, for 30 metres or more from the shore, had a thin film of ice covering it.

Ice, ice baby

As the tide dropped the shore was left with a sparkling crust of 1mm thick glass-like ice confetti.

The salinity of seawater is typically ~3.5% … this amount of salt reduces the freezing point to about -2°C, a temperature we’ve regularly experienced in the last fortnight. This suggests the ‘strange’ conditions were probably the absence of any swell coupled with the really calm conditions.

Whatever the cause, it was beautiful.

Early season forage … you must be joking 😉

Under conditions like these the bees are effectively invisible. They’re very tightly clustered . With daytime temperatures rarely reaching 3°C none venture out of the hive. With the exception of cleansing flights and the removal of corpses – and it’s too cold for either of these – there’s little reason for them to leave the hive anyway.

The gorse is in flower … somewhere under there

The only thing flowering is gorse and it would be a foolhardy bee that attempted to collect pollen at the moment.

I’ve previously written about the genetically-determined flowering time of gorse. In an attempt to improve forage at certain times of the year I’ve been collecting seed from suitable plants and germinating it indoors. As soon as the weather improves I’ll plant these seedlings out ² as the amount of gorse around the apiary is quite limited.

Gorse (and some broom) seedlings

Gorse seed is painful to collect and germinates poorly. I pour boiling water over the seed and then let it soak for 24 hours, which improves germination at least ten-fold.

Hive checks

Every fortnight or so I check the hive weights by hefting. Only two colonies have had any extra fondant yet and that was through ‘an abundance of caution’. I suspect they actually didn’t really need it.

The next eight weeks (here ³ ) is when brood rearing should be starting to really ramp up. It’s during February and March that starvation is an issue.

Here on the west coast, my colonies are rearing brood. This tray has been in for about a week. I’m including it as I’ve been asked several times about how to determine if a colony is rearing brood without opening the hive.

Biscuit coloured (or a bit darker) cappings indicating brood rearing in this colony

The red arrows indicate the biscuit coloured cappings that have fallen from the seams in which they are rearing brood. The inset shows a magnification of the indicated part of the image. The photo was taken with a camera phone and the cappings are perhaps a bit darker than usual (though I also know there are a few older brood frames in this hive 🙁 ).

And if the conditions are right, even with a well-insulated poly hive, you can identify which wall the cluster is up against by the evaporation of the overnight damp from the outer surface of the hive.

The location of the cluster is clearly visible on this Abelo poly hive

This is the front of the same hive from which the Varroa tray was photographed – the cappings on the tray and the cluster location correspond perfectly.

By the way … don’t bother looking for Varroa on the tray. This hive is in a Varroa-free region 🙂

As I’ve said before, it’s not unusual for colonies in poly hives to cluster tightly against the wall in winter. Those in cedar are more often away from the wall in my experience (and the same thing applies to brood rearing other than at the height of the season).

Hey good lookin’

The Abelo hive above is a nice looking box. The paint finish is bonded well to the polystyrene and provides good protection.

If you leave unpainted polystyrene out in the elements it starts to look pretty tired, pretty quickly.

I don’t have any pictures as none of my poly hives are unpainted.

At least, none are any more 😉

I’d acquired some new Maisemores nucs with bees and had a number of unused and unpainted Everynucs. Most manufacturers recommend you paint poly hives with masonry paint of some kind, or they sell (often quite pricey) paint that’s suitable.

Everynuc poly nucs

I’ve painted a lot of nucs with masonry paint, using a paint spray gun. It goes on fast and is reasonably hardwearing … but not great.

Swienty brood box …

In contrast, my Swienty brood boxes look as good now as when they were first painted 5 years ago. These received two coats of ‘Buckingham green’ Hammerite Garage Door paint.

This paint is designed for galvanised metal garage doors (the clue is in the name 😉 ). It contains a bunch of unpleasant sounding solvents but, when dry, appears to be entirely safe. I’d recommend not reading the 13 pages of safety data sheets or you might never dare open the tin because of the imminent risk of explosion.

Melting polystyrene

These solvents have the effect of slightly ‘melting’ the surface of the poly hive. This creates a really strong bond between the paint and the hive surface. The melting isn’t enough that you can notice the surface texture change … it’s just an invisible chemical reaction going on as you brush the stuff on.

Maisemore’s poly nuc after the first coat

However, this reaction might account for the rather patchy coverage of a single coat. If you paint it on thickly enough to try and produce a nice even finish it tends to run and sag a bit.

So give it two coats … and then it looks excellent.

Oxbridge Blues – a few painted poly nucs ready for the season ahead

Several months ago I bought a ‘remaindered’ tin of Hammerite paint in Oxford blue. I had wanted a contrasting colour (to my other boxes) for these nucs to help orientate returning freshly mated queens.

I paint the entire box, avoiding any of the ‘touching’ faces which are left unpainted. Some paint usually seeps into joins between the roof, body and/or floor, but you can easily prise them apart with a judiciously applied hive tool.

I’m rather pleased with how smart they now look.

I’m somewhat less pleased with the quality control on some of the Everynucs ⁴. Several had the mesh floor stuck down incorrectly, with parts unattached. In places the gaps were big enough for a bee to enter.

Open mesh floor and big gap at the side in an Everynuc

I simply pulled them off and restuck them down with a glue gun. This is an easy fix but really should not be necessary on a nuc box that costs almost £60 🙁

A+E

With the current Covid pandemic we have a responsibility to minimise the demands we are placing on our heroically overstretched healthcare workers.

For this reason I’ve been avoiding doing any DIY for beekeeping for many months now 😉

However, the season is looming ever-closer and I want to try some new things.

My toolbox contains approximately equal amounts of disconcertingly sharp implements and elastoplast. I’m well prepared 😉

I’m also currently living very remotely. In the event of a bad injury I’m unlikely to ever trouble the staff in A+E … unless the accident conveniently coincides with the ferry timetable 🙁

I therefore decided to risk life and limb by building the things I need to try queen rearing using a Morris board.

I’ll describe full details of the method later in the year.

For me, this method should offer advantages due to the type of bees, the size of my colonies, the number of queens I want to rear and the period over which I want to rear them.

You can buy these boards (for about £30 each) … or you can build better ones for about a fiver from offcuts from the wood bin, a bit of queen excluder and a piece of aluminium. They are a bit fiddly to build, with four opening doors and a ‘queenproof’ slide, but the cost savings and satisfaction you gain more than outweigh the blood loss involved.

Here’s one I started earlier … a Morris board under construction

The very fact I’m still able to write this post shows that I managed to retain all my fingers. Whether or not the Morris board works ⁵ I consider that fact alone a success 🙂

Doing the splits

The Morris board works by allowing access to 5 frame upper brood box for defined periods. I therefore also needed a brood box divided in half.

I’ve been doing a lot of wax extracting recently and a couple of cedar boxes have cracked under the stress of repeated steam cycles. I split one down to its component boards, burning the bits that were unusable, but recycling one side into the central division of another old cedar box.

Split brood box – detailed view of my very poor workmanship

I’ll be queen rearing in two apiaries simultaneously, so will need two of these upper boxes. However, I only managed to salvage one sufficiently large board from the steam-damaged box. Fortunately I have some cedar nucs built precisely (so clearly not by me 😉 ⁶ ) to National hive dimensions, so I can use two of these side-by-side with the same design Morris board.

Late afternoon sun, 24^th January

But queen rearing remains both a distant memory and a very long way off in the future. Until then it’s a case of enjoying the short winter days and drinking cappuccino in front of the fire.

Good times

Notes

Hammerite Garage Door paint is usually £15-20 a tin (750 ml). It’s worth shopping around as there’s quite a bit of variation. I found it remaindered and paid under a tenner 🙂

I reckon there’s enough in one tin to do two coats on 9-10 nucs as long as you take care not to over apply the first one. You could probably thin it a bit (though I’m not sure what with ⁷) but I’d take care you don’t create something that just melts the poly box.

Even at £20 it still works out at only about £2 a nuc. Considering these can cost £40-60 it seems like a reasonable investment of money to keep them looking smart for years.

And a good investment of time (it took me ~15-20 minutes per coat) … after all, what else are you going to do in the bleak midwinter?

The winter cluster

We had our first snow of the year last night and the temperature hasn’t climbed above 3°C all day. The hills look lovely and, unsurprisingly, I’ve not seen a single bee venturing out of the hives.

Winter wonderland

If you crouch down close to the hive entrance and listen very carefully you’ll be able to hear …

… absolutely nothing.

Oh no! Are they still alive? Maybe the cold has killed them already?

If you rap your knuckles against the sidewall of the brood chamber you’ll hear a brief agitated buzz that will quickly die back down to silence.

Don’t do that 😯

Don’t disturb them unless you absolutely have to. They’re very busy in there, huddling together, clustering to maintain a very carefully regulated temperature.

Bees and degrees

Any bee that did venture forth at 3°C would get chilled very rapidly. Although the wing muscles generate a lot of heat (see below), this uses a large amount of energy.

If the body temperature of an individual bee dips below ~5.5°C they become semi-comatose. They lose the ability to move, or warm themselves up again. Below -2°C the tissues and haemolymph starts to freeze.

However, as long as they’re not exposed to prolonged chilling (more than 1 hour) they can recover if the environmental temperature increases ¹.

An individual bee has a large surface area to volume ratio, so rapidly loses heat. Their hairy little bodies help, but it’s no match for prolonged exposure to a cold environment.

But the bees in your hives are not individuals. Now, perhaps more than any other time in the season, they function as a colony. Survival, even for a few minutes at these temperatures, is dependent upon the insulation and thermoregulation provided by the cluster.

All for one, one for all

The temperature in the clustered colony is always above the coma-inducing 5.5°C threshold, even for the bees that form the outer surface layer, which is termed the mantle.

And the temperature in the core of the cluster is much warmer still, and if they’re rearing brood (as they soon will be ²) is maintained very accurately.

The mantle

The temperature inside the hive entrance, some distance from the cluster, is the same as the external ambient temperature. On a cold winter night that might be -5°C (in Fife), or -35°C (in Manitoba).

Studies have shown that clustered colonies can survive -80°C for 12 hours, so just a few degrees below freezing is almost balmy.

The winter cluster

Due to thermal radiation from the clustered colony, the temperature of the airspace around the colony increases as you get nearer the cluster. Draught free hives – and beekeepers that refrain from rapping on the brood box sidewall – will reduce movement of this air, so reducing thermal losses from convection.

The clustered colony is not a uniform ‘ball’ of bees. It has two distinct layers. The outer layer is termed the mantle and is very tightly packed with bees facing inwards. These bees are packed in so tightly that their hairy bodies trap air between them, effectively forming an insulating quilt.

To reduce heat loss further these mantle bees have a countercurrent heat exchanger (between the abdomen and the thorax) that reduces heat loss from the haemolymph circulating through their projecting abdomens.

The mantle temperature is maintained no lower than about 8°C, safely above coma-inducing lower temperatures.

Penguins and flight muscles

I’ve seen it suggested that the mantle bees circulate back into the centre of the cluster to warm up again, but have been unable to find published evidence supporting this. It’s an attractive idea, and it’s exactly what penguins do on the Antarctic ice sheet … but that doesn’t mean it’s what bees do.

Penguins, not bees

Although bees can cope with temperatures of 8°C, they cannot survive this temperature for extended periods. If bees are chilled to below 10°C for 48 hours they usually die. This would support periodically recirculating into the centre of the cluster to warm up.

Bees do have the ability to warm themselves by isometric flexing of their flight muscles. Essentially they flex the opposing muscles that raise and lower the wings, without actually moving the wings at all.

This generates a substantial amount of heat. On a cool day, bees warm their flight muscles by this isometric flexing before leaving on foraging flights. They have to do this as the flight muscles must reach 27°C to generate the wing frequency to actually achieve flight. Since bees will happily forage above ~10°C this demonstrates that the isometric wing flexing can raise the thoracic flight muscle temperature by at least 15-17°C.

But, briefly back to the penguin-like behaviour of bees, neuronal activity is reduced at lower temperatures. In fact, at temperatures below 18°C bees don’t have sufficient neuronal activity to activate the flight muscles for heat generation. This again suggests there is a periodic recycling of bees from the mantle to the centre of the cluster.

How can bees fly on cool days if it’s below this 18°C threshold? The day might be cooler, but the bee isn’t. The colony temperatures are high enough to allow sufficient neuronal activity for the foragers to pre-warm their flight muscles to forage on cool days.

Anyway, enough of a digression about flight muscles, onward and inward.

The core

Inside the mantle is the core. This is less densely occupied by bees, meaning that they have space to move around for essential activities such as brood rearing or feeding.

The temperature of the core varies according to whether the colony is rearing brood or not. If the colony is broodless the core temperature is maintained around 18°C.

The tightly packed mantle bees reduce airflow to the core. As a consequence of this the CO₂ levels rise and the O₂ levels fall, to about 5% and 15% respectively (from 0.04% CO₂ and 21% O₂ in air). A consequence of this is that the metabolic rate of bees in the core is decreased, so reducing food consumption and minimising the heat losses from respiration.

Brood rearing

My clustered winter colonies are probably just thinking about starting to rear brood ³.

Bees cannot rear brood at 18°C. Brood rearing is very temperature sensitive and occurs optimally at 34.5-35.5°C.

Outside that narrow temperature band things start to go a bit haywire.

Pupae reared at 32°C emerge looking normal (albeit a day or so later than the expected 21 days for a worker bee), but show aberrant behaviour. For example, they perform the waggle dance less enthusiastically and less accurately ⁴. In comparison to bees reared at 35°C, the ‘cool’ bees performed only 20% of the circuits and the ‘waggle run’ component was a less accurate predictor of distance to the food source.

Neurological examination of bees reared at 35°C showed they had increased neuronal connections to the mushroom bodies in the brain, when compared with those reared as little as 1°C warmer or cooler. This, and the behavioural consequences, shows how critical the brood nest temperature is.

The cluster position

The cartoon above shows the cluster located centrally in the hive. This isn’t unusual, though the cluster does tend to move about within the volume available as they utilise the stores.

You can readily determine the location of the cluster. Either insert a Varroa tray underneath an open mesh floor for a few days …

Tell tale signs of a brood-rearing cluster …

… or by using a perspex crownboard. I have these on many of my colonies and it’s a convenient way of determining the size and location of the cluster with minimal disturbance to the colony.

Perspex crownboard …

Though you don’t need to check on them like this at all.

The photograph above was from late November (6 years ago). The brood box is cedar and therefore provides relatively poor insulation.

While checking the post-treatment Varroa drop in my colonies this winter it was obvious that cluster position varied significantly between cedar and poly hive types.

In poly hives (all my poly hives are either Abelo or Swienty) it wasn’t unusual to find the cluster tight up against one of the exterior side walls. In contrast, colonies hived in cedar brood boxes tended to be much more central.

This must be due to the better insulation of polystyrene compared with cedar.

Insulation

Although I don’t think I’ve noticed this previously in the winter, it’s not uncommon in summer to find a colony in a poly hive rearing brood on the outer side of the frames adjacent to the hive wall. This is relatively rare in cedar boxes, other than perhaps at the peak of the summer.

If you’re interested in hive insulation, colony clustering and humidity I can recommend trying to read this paper by Derek Mitchell.

I don’t provide additional insulation to my colonies in the winter. It’s worth noting that all my hives have open mesh floors. In addition, the crownboard is topped by a 5 cm thick block of insulation throughout the year, either integrated into the crownboard or just stacked on top.

Perspex crownboard with integrated insulation

If you use perspex crownboards you must have insulation immediately above them. If you don’t you get significant amounts of condensation forming on the underside which then drips down onto the cluster.

The winter cluster and miticide treatment

The only time you’re likely to see the winter cluster is when treating with an oxalic acid-containing miticide. And only then when trickle treating.

With the choice between vaporising or trickle treating, I tend to be influenced by the ambient temperature.

If the cluster is very tightly clustered (because it’s cold) I tend to trickle treat.

If it is more loosely clustered I’m more likely to vaporise.

The threshold temperature is probably about 8°C, but I’m not precious about this. The logic – what little is applied – is that the oxalic acid crystals permeate the open cluster better than they would a closed cluster.

I’ve got zero evidence that this actually happens 😉

However, it’s worth reiterating the point I made earlier about airflow through the mantle. Since this is restricted in a tightly clustered colony – evidenced by the reduced O₂ and elevated CO₂ levels – then it seems reasonable to think that OA crystals are less likely to penetrate it either.

Of course, there’s an assumption that the trickled treatment can penetrate the cluster, and doesn’t just coat the mantle bees with a sticky OA solution.

Which neatly brings us back to penguins … if these mantle bees do recirculate through the cluster core they’ll take some of the OA with them, even if it didn’t get there directly.

Finally, it’s worth noting that cluster formation starts at about 14°C. As the temperature drops the cluster packs together more tightly. Between 14°C and -10°C the volume of the cluster reduces by five-fold.

By my calculations ⁵, at 2°C and 8°C the cluster is three and four times it’s minimal volume respectively, so perhaps both OA vapour and trickled solution could permeate perfectly well.