Saturday, March 18, 2023
HomeBeeKeepingReminiscence, longevity and sunflowers - The Apiarist

Reminiscence, longevity and sunflowers – The Apiarist

Synopsis : Shifting hives in winter, the diminished (or not) longevity of honey bees and the advantages of sunflowers. Certainly there’s one thing that pursuits you right here?


Don’t sigh disappointedly and look elsewhere for the definitive put up on ”Horny beesuits for a scorching summer season” or “The ten finest hives instruments of 2023” . Regardless of file breaking February climate and my report of early frogspawn, the temperatures have subsequently plummeted, it’s snowed once more and the beekeeping season feels as far-off as ever.

Solar and snow

I’ve subsequently obtained no sensible beekeeping to debate 🙁 .

All I’ve carried out since final week is mix and jar honey, stare balefully out of the window on the hives (obscured by falling snow) and construct frames.

And who desires to examine that?

What’s extra, the chilly snap isn’t restricted to my remoted nook of Scotland. While I might write about first inspections, or getting ready for the OSR, all of it feels a bit untimely. A decade of observing the web page stats right here exhibits that articles are learn most once they’re well timed. A lot of web page views boosts my promoting income so I need to write well timed articles which might be extensively learn.

I’m subsequently going to jot down about some science(y) stuff as an alternative. You could have seen the headlines related to one in every of these research, however you’re unlikely to have learn the article. I had been intending to begin a month-to-month e-newsletter to cowl a few of these beekeeping-related subjects that had been unsuitable for a full put up.

‘Unsuitable’ for a wide range of causes; not very attention-grabbing however actually necessary, sounds necessary however in all probability isn’t, attention-grabbing however inconclusive, attention-grabbing however mistaken and many others.

Nonetheless, I’m too busy to jot down greater than I already do, so as an alternative I’ll periodically have a ’Science snippets’ put up and lump a number of subjects collectively, prefixed this week with some musings from observations on transferring hives.

One thing for everybody? … or Nothing for anybody? … time will inform 😉 .

The reminiscence of bees

Earlier than you all disappear to look of that hive software article I’ll focus on transferring hives in winter.

I’m getting some constructing work carried out shortly and wanted to maneuver 4 hives to a different location.

Moved hives

Through the beekeeping season – or, extra precisely, when the bees are flying freely – the lower than three toes and greater than three miles rule applies when transferring hives.

Most beekeepers have heard of this (or a variant thereof). Foragers orientate to the placement of the hive, utilizing pure landmarks and their somewhat elegant homing means to return to the hive. It’s normally reckoned that bees could journey as much as 3 miles whereas foraging. Sometimes it’s lower than this, and scientific research have proven it may be fairly a bit additional, however 3 miles is a helpful determine to cite.

The ultimate strategy is made utilizing a mix of visible and olfactory clues. These are quick vary. Due to this fact, when you transfer the hive a brief distance (the ’lower than 3 toes’) they’ll nonetheless discover it, however when you transfer them greater than three miles they are going to reorientate to the brand new location and never return to the unique web site.

None of those distances are exact; they’ll nonetheless discover the hive when you transfer it 1 metre (3 toes and three inches), and doubtless gained’t return when you transfer a hive 2.5 miles, however you get the thought.

Nonetheless, within the winter when the bees are usually not flying, it’s assumed by many who these guidelines don’t apply.

And, I’m together with myself within the ‘assumed by many’ group.

‘Assumed’ can imply not understood correctly 😉

The reasoning goes one thing like this;

  • the temperature is simply too low for flying and the bees are confined to the hive and have been for weeks.
  • bees have small brains with no need for long-term feats of reminiscence (in any case most reside lower than 6 weeks).
  • when a winter ‘flying day’ does happen, they are going to refresh their reminiscence of the hive location, successfully taking an orientation flight. Reinforcement happens on successive winter flying days, even when these are primarily for cleaning flights or water assortment.

Due to this fact, after a protracted interval of low temperatures with no flying days, you may safely transfer hives intermediate distances (between 3 toes and three miles) with out risking bees returning to the unique location when the climate does heat.

In order that’s what I did.

Flying bees

The bees had been flying effectively on the 20th of December (12°C) however I’d seen no bees flying in January or early February. We’d had solely three or 4 days throughout that interval when the temperature (simply) exceeded 9°C, however accompanied by loads of rain as effectively.

In mid-February (the 14th) I moved the hives about 50 metres to the brand new web site. I used to be cautious to not disturb the cluster and left the doorway sealed for half-hour after transferring the containers. No bees flew once I eliminated the doorway blocks.

On the 25th the solar got here out for an hour or two and so did the bees 🙂 .

Misplaced bees

And, though the bulk went on what clearly appeared like orientation flights, a few hundred returned to their unique location by the shed. I worry these perished because the temperature dived to ~4°C when the solar disappeared and there was frost by night.

(Some) winter bees have fairly long run reminiscence

While clearly individually tragic, the loss of some hundred bees isn’t going to jeopardise the moved hives, although I’d favor to not lose any. A subsequent fast peak when topping up the fondant confirmed that they’re effectively populated and doing effectively.

Had I carried out the identical transfer in the summertime there would have been hundreds of bees milling across the unique web site by the shed. However that is winter and the winter bees that now populate the hives have largely been in residence for months.

So, throughout their incarceration, the majority of winter bees seem to have forgotten the unique location … however not all of them.

How lengthy had they been incarcerated?

Eight weeks had elapsed between the 20th of December and the day I moved the hives. I first noticed bees flying 11 days later, so nearly 10 weeks in complete. I could have missed bees flying inside that interval, however the unique web site was inside 10 metres of the again door and in full view. The climate has been poor and I’ve been working outdoors when it was even vaguely affordable.

My searches of the scientific literature failed to show up something on the long-term reminiscence of winter bees. There are some attention-grabbing observations by Vyas et al., (2021) on ‘long run’ reminiscence however these are of summer season foragers and feeder areas. Vyas’s definition of ‘long run’ on this examine is just 7 days.

Unanswered questions

A lot of bees had been flying on the 25th. Nonetheless, solely a small proportion returned to the ‘mistaken’ location.

Why do solely a subset of winter bees retain the reminiscence of the unique location? Are these the youngest winter bees, or simply people who made the final flights from the outdated web site?

Or maybe they’re the oldest and made probably the most return flights to the unique web site? Reinforcement is understood to assist prepare bees to recollect geographic areas.

The colonies are rearing brood, however not an enormous quantity. Among the orientating bees on the 25th had been prone to be new staff, however the inhabitants of winter bees will nonetheless vastly exceed the few hundred that had been ’lacking in motion’ on the primary flying day in weeks.

On subsequent flying days I’ve not seen any extra bees across the unique hive location. This additional reinforces my view that the flight on the 25th was the primary for weeks.

Might I’ve moved the colonies with out dropping these bees?

Not simply.

If winter bees have lengthy reminiscences the summer season trick of transferring them away for 3 weeks (throughout which period all the present foragers die) after which transferring them again wouldn’t work. Nonetheless, the choice, transferring them a metre at a time, down a steep rocky slope, was each wildly impractical and stupidly reckless .

Bees live half so long as they used to

This paper made fairly a splash and obtained loads of mentions within the common press. Two or three readers emailed me about it, both to carry it to my consideration or ask whether or not it was the reason for their misplaced colonies.

It’s nearly sure the rationale they’d misplaced colonies this winter is Varroa … it all the time is .

The title of the examine (by Nearman and van Englesdorp, 2022) is a bit convoluted … ’Water provisioning will increase caged employee bee lifespan and caged employee bees live half so long as noticed 50 years in the past’.

The second declare, ‘residing half as lengthy’ was – unsurprisingly – the one which captured everybody’s consideration. Because it’s broadly acknowledged that bees are threatened with extinction (they’re not) and are declining (they’re not) then maybe the easy indisputable fact that they’re ’turning up their tarsi’ twice as quick as they did 5 many years in the past explains every part.


I believe the authors had been finding out one thing else utterly and realised, probably when controls, that bees given syrup and water did higher in laboratory cages than these simply given syrup. They then checked the literature to work out if this differential ‘higher’ has all the time been the case … solely to find that ‘higher’ within the 1970’s was twice so long as ‘higher’ within the 2020’s.

Or one thing like that.

It’s commonplace to begin finding out one factor and find yourself publishing one thing totally different .

The longevity of caged bees and the productiveness of colonies

If you wish to examine the impact of pesticides, viruses or no matter else on bees you’ve the selection of:

  • doing observational science of bees in a hive i.e. rely or in any other case measure issues in regards to the hive and decide whether or not the pesticide, virus, no matter is current/absent, and at what stage. Then search for correlations.
  • conducting lab-base experiments with bees in cages, subjected to totally different quantities of pesticides, viruses or no matter. Is there a dose-response? Do extra ‘whatevers’ assist or hinder the bees?

And it’s the latter sort of examine that Nearmann and van Englesdorp had been doing. The newly emerged bees had been saved in plastic meals trays in an incubator.

Median lifespan of caged bees

Having labored out that their bees had a median lifespan of ~21 days they then checked out 46 printed research since 1970 the place the median survival was decided utilizing caged bees. The lifespans decreased from ~34 days in 1970 to solely ~18 days in 2019.


If foragers live much less lengthy it will be anticipated that honey yields can be diminished as a result of colonies can be smaller (and so much less productive).

Have honey yields diminished over the past 50 years?

Luckily, these kinds of issues had been recorded by the Nationwide Agriculture Statistic Service (NASS) within the USA since 1987.

Median longevity and honey manufacturing

There was a optimistic correlation between the measured or predicted employee lifespan and the honey yield per colony.

Correlation doesn’t imply causation, however it’s definitely attention-grabbing that yields per colony seem to cut back because the lifespan of the employee bees will get shorter.

The authors additionally did a bunch of in silico modelling utilizing BEEHAVE however I’m going to skip this bit and as an alternative concentrate on the ‘easy’ elements of longevity and the quantity of honey produced.

Evaluating ‘like with like’

The comparisons of 1970’s bee longevity with bees from the 21st century are legitimate if the research are performed in the identical method. They in all probability weren’t. The higher graph above exhibits that pre-1990 research tended to incorporate extra bees per cage (bigger blobs) and the authors acknowledge that this influences employee longevity.

However what had been the bees caged in? Nowadays we use sandwich containers, or (unused!) carry-out meals containers. Within the 70’s the cages would have nearly definitely been wooden with internet or mesh sides. Generally these items can be documented within the supplies and strategies, however typically they’re omitted and researchers simply assume everybody is aware of you retain bees in a sure cage sort (forgetting that the examine would possibly solely change into attention-grabbing 50 years later).

So I’m fairly sceptical that the longevity reductions are really primarily based upon a like for like comparability. I’m additionally a bit cautious of the big variety of 1970’s research that report excessive longevity of staff (>40 days).

The median longevity of bees would possibly be lowering, however I’d need to see a number of the early research reproduced in precisely the identical strategy to have extra confidence.

What in regards to the honey yields?

The figures quotes are nearly definitely from industrial beekeeping operations (bear in mind it was NASS that had been gathering them). To make more cash, industrial beekeepers want huge, sturdy hives.

Nonetheless, to make even extra money (and it’s in all probability nonetheless not loads 🙁 ), beefarmers more and more cut up the colonies and ship them off to California in February for almond pollination. Almond acreage has in all probability greater than quadrupled since 1990, so needing extra hives. Fee is per hive, so extra reasonable sized colonies generates extra income than fewer giant colonies. 

Widespread sense

This paper was mentioned fairly broadly on the Bee-L scientific dialogue group. It’s value a learn to see the vary of views expressed. I believe it’s honest to say that many contributors had been fairly sceptical of the conclusions of the paper, or a minimum of of the title.

However earlier than I depart the subject let’s take into consideration a number of different elements that would affect issues.

What’s a direct consequence of diminished longevity of employee bees? Assuming what’s noticed within the lab displays what occurs ‘within the subject’ (and absolutely the determine of 18 days suggests it isn’t as that’s lower than staff keep as hive bees), then the colonies will probably be smaller.

Are colonies smaller now than they had been 25 or 50 years in the past? Appreciably smaller? They might be if the employee lifespan was halved.

I believe this could have been apparent.

OK, let’s assume the colonies now are about the identical dimension. If the median lifespan of staff is halved the solely method the colony might be the identical dimension – whether or not measured in containers of bees, or numbers of staff – is that if the queen lays much more eggs per day.

Once more, Bee-L has some restricted dialogue of this, however I believe the consensus of those that have been retaining bees because the 1970’s was that colony dimension and queen fecundity haven’t dramatically modified.

Two different issues that will have modified within the intervening interval are forage availability and pathogen (significantly deformed wing virus) ranges. Have been these the identical?

The paper has a intelligent title … however I stay to be satisfied it exhibits what the authors suppose it exhibits.

The title, like my ‘Horny beesuits for a scorching summer season’, definitely invitations consideration, however ultimately the reader is left somewhat underwhelmed.

Sunflowers and diminished Varroa ranges

By the use of a distinction, right here’s a latest examine that:

  • entails complete hive evaluation somewhat than considerably synthetic in vitro research
  • makes use of present knowledge and a standardised methodology
  • you in all probability haven’t seen

And which, though I believe it’s attention-grabbing, will not be fairly pretty much as good because it sounds, or fairly as promising for UK beekeepers because it might be.

Quite a few research have proven that, whereas the pollen is low in protein, many bugs that forage on members of the Asteraceae household (which incorporates sunflowers, Helianthus annuus) have diminished ranges of pathogens and parasites.


Does this additionally apply to honey bees?

Utilizing a typical evaluation technique (alcohol wash to measure phoretic mites per 100 bees) the authors (Palmer-Younger et al., 2023) measured mite ranges in August and September (sunflowers are late flowering) in dozens of apiaries and recorded the acreage of sunflowers inside 2 miles, see A under.

Sunflower foraging (A) and pollen (B) reduces mite ranges. Dotted line = 3% therapy threshold.

There was a correlation; the extra sunflowers the bees might forage on, the decrease the mite ranges.

Which isn’t fairly the identical as saying the extra sunflowers the bees foraged for pollen on the decrease the mite ranges.

So that they measured the implications of that as effectively.

33 colonies throughout 5 websites had been supplemented for five weeks in Could and June with pollen patties containing wildflower pollen, sunflower pollen or synthetic pollen (BeePro). All colonies had low mite ranges firstly of the examine. After feeding the mite ranges had been measured once more and people fed sunflower pollen patties had the bottom mite ranges (B, above), although the variations weren’t statistically important.

Sounds promising; what’s taking place and may I begin getting excited?

I’ve intentionally skipped loads of the leads to the Palmer-Younger et al., (2023) examine, both as a result of they present no measurable variations – e.g. in virus or Nosema ranges – or as a result of they distract from the tempting-looking correlation between low mite ranges and foraging on sunflowers.

How would possibly this be defined? What are the chances?

There are three apparent explanations – which I’ve offered within the order of probability (least to most) so far as I’m involved:

  1. sunflower pollen per se or, extra seemingly (as mites don’t eat pollen straight), a secondary metabolite produced from sunflower pollen in bee pupae, is poisonous to Varroa
  2. honey bee pupae reared on sunflower pollen are much less nutritious to Varroa – somewhat than being poisonous to the mites, the latter are merely much less effectively fed and so reproduce much less effectively
  3. colonies feeding on sunflower pollen produce much less brood and so Varroa has fewer pupae to breed on

Time will inform which of those is appropriate or if there’s a unique clarification altogether. The primary can be nice as you can purify the toxin and administer it straight, the third can be worrying as weak, poorly fed, colonies in late summer season could undergo excessive overwintering losses (regardless of the mite ranges).

What? You don’t care in regards to the clarification, you simply need to plonk your colonies subsequent to acres of sunflowers and reap the advantages?

Honest sufficient … however there’s one other drawback. Palmer-Younger et al., present that sunflower acreages within the US are steadily declining (by ~2%/annum over the past 4 many years).

Over right here within the UK they’re already at very low ranges and might’t decline a lot with out disappearing. A lot of the nation is simply too chilly for sunflowers. Though southern Britain would possibly have the ability to accommodate 60,000 hectares, solely about 600 hectares are literally grown 🙁 .


One last thought on the reminiscence of winter bees (included right here because it’s now too late to vary the textual content above). Though I’d not seen any bees flying between the 20th of December and mid-February, I acknowledge I’ll have missed a number of taking cleaning or water flights. Maybe the one ones that ended up ‘lacking in motion’ after transferring the hives had been the few that had flown since December.

It will be attention-grabbing, although maybe a bit merciless, to maneuver winter colonies after recognized extended intervals with no flying exercise to find out the reminiscence of those diutinus bees. Alternatively, you can mark staff getting back from cleaning flights, then subsequently transfer the hive and see whether it is predominantly these staff that find yourself being misplaced.

However in fact that will imply I’d have needed to see them flying … and I haven’t.



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