Tag Archives: drones

Polyandry and colony fitness

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

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

Colony fitness

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

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

Shallow depth of field

One of many …

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

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

The benefits of polyandry

Why should colonies with increased genetic diversity be fitter?

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

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

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

Does polyandry contribute to Varroa resistance? 

Would increased polyandry result in improved resistance to mites?

Limits of polyandry and natural resistance

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

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

How could this be tested?

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

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

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

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

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

Yes.

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

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

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

Brood frame with a good laying pattern

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

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

Natural Varroa resistance and polyandry

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

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

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

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

Marked queen surrounded by a retinue of workers.

Her majesty …

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

No.

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

On average, Arnot Forest queens had mated with ~18 drones (17.8 ± 9.8) each. In contrast, queens in managed colonies in two nearby apiaries had mated with ~16 and ~21 drones. These figures are not statistically different from each other or from the natural mating frequencies reported for honey bees in other studies.

Hyperpolyandry and colony fitness

The first of the studies confirms and extends earlier work demonstrating the polyandry (and in this instance hyperpolyandry i.e. at an even greater level than seen normally) increases colony fitness – at least in terms of colony strength and Varroa resistance.

Delaplane and colleagues hypothesise that the increased mite resistance in hyperpolyandrous (30 or 60 drones) colonies may be explained by either:

  • the importance of extremely rare alleles (gene variants), which would only be present in colonies in which the queen had mated with a very large number of drones.
  • the presence of beneficial non-additive interactions between genetically-determined traits e.g. grooming and hygienic behaviour and reduced mite reproduction.

Neither of which are mutually exclusive and both fit at least some of the extant data on natural mite resistance. Discriminating between these two hypotheses and teasing apart the variables will not be straightforward.

Absence of hyperpolyandry in naturally mite-resistant colonies

At first glance, the absence of the hyperpolyandry in the mite-resistant Arnot Forest bees studied by Thomas Seeley and colleagues appears to contradict the studies using the instrumentally inseminated queens.

The Arnot Forest bees exhibit the same level of polyandry as nearby managed colonies, and for that matter, as colonies studied elsewhere. They are mite-resistant but the queen has not mated with an increased number of drones.

In other studies 9, naturally mated colonies exhibiting different levels of polyandry (within the normal range) showed no correlation between Varroa levels and queen mating frequency.

Perhaps it’s surprising that the Arnot Forest queens hadn’t mated with fewer drones considering the extreme separation of the colonies (when compared with managed colonies). The colony density within the Forest is approximately one per square kilometre.

However, at least during the peak swarming and mating period in the season, drone availability is rarely limiting.

This is because drones are not evenly spread in the environment. Instead, they accumulate in drone congregation areas (DCA) to which the queen flies for mating.

What limits polyandry?

Polyandry is beneficial and, apparently, hyperpolyandry is more beneficial. However, queens mate with 10 – 20 drones, rather than 50 or more. Why is this?

Queen mating is a risky business. The queen has to fly to the DCA, mate with multiple drones and then return to the hive. She may make one or several mating flights.

I’ve discussed how far drones and queens fly to reach the DCA previously. Most drones fly less than 3 miles and 90% of matings occur within about 5 miles of the virgin queen’s hive. The queen probably flies further to the DCA.

All the time she is travelling to and from the DCA, and all the time she is present within it mating, she’s potentially at risk from hungry house martins, swallows, bee eaters (!) or from thunderstorms.

Or simply from getting lost.

Additionally, a number of honey bee pathogens are transmitted between drones and queens during mating. Hyperpolyandrous queens 10 are therefore at risk from these sexually transmitted diseases 11.

It’s therefore likely that the level of polyandry observed in honey bees has evolved as a consequence of the beneficial pressures polyandry brings balanced by the risks associated with mating multiple times.

Practical beekeeping

Although the two studies described here don’t have an immediate relevance to day-to-day practical beekeeping, it’s worth remembering that poor queen mating is regularly blamed for queen failures e.g. queens that develop into drone layers during the winter.

I’m going to write about drones later this year so for the moment will just make these points:

  • drone production is maximised to generate sexually mature drones for the swarming season
  • after eclosion, drones need to mature before being able to mate
  • drones live about 30 days and their sperm volume, though not necessarily viability, decreases as they age

Together this means that late in the season – perhaps late July or early August (though this will vary depending upon location) – the number of drones will decrease.

More significantly, the drones will be ageing.

In turn this means that late-mated queens may not mate with as many drones, or that the matings may not result in insemination.

Most beekeepers will be aware of queens that apparently ‘run out of sperm’ and become drone layers.

However, there may be less obvious problems with late-mated queens. I’m not aware of any studies on seasonality of queen mating and polyandry. However, I would not be at all surprised if they exhibited a reduced level of polyandry.

And, as described above, these colonies are likely to exhibit reduced fitness.

Something else to consider when deciding whether to unite a colony late in the season or hope the last of your virgin queens mates successfully …


 

Foundationless frames reviewed

New comb ...

New comb …

One of the big successes of this season has been the use of foundationless frames. These have reduced my use of foundation by over 75%, leading to a significant accumulation of unused packets which were ordered before the season started (as an aside, if stored flat in a cool place foundation should be OK for years, simply needing a quick blast with a hairdryer to remove the pale bloom that appears). Aside from the economic benefits, I’m convinced that the bees draw comb on foundationless frames at least as fast as they do on frames with foundation. In some cases, given the choice, the queen also starts laying in the foundationless comb earlier. Finally, they are an ideal way to prepare a bait hive, providing the volume the scout bees are seeking coupled with the ‘order’ that will ensure that any swarm will build comb where you want it.

Foundationless frames

Super frames …

Preparing new foundationless frames takes a litte more effort – you need to drill the sidebars and ‘wire’ them with nylon monofilament fishing line before adding a narrow starter strip. At least, that’s what I do. In my view this effort is more than offset by the benefits they provide. Framebuilding is made almost pleasurable by using a nail gun … look out for special offers on these from Amazon where a suitable model (Tacwise EL191) was recently reduced to under £40.

Foundationless frames also work well in supers. I prepared a few boxes of these this season and extracted them using a radial extractor. With a couple of exceptions the frames all survived. The only two that collapsed were either partially drawn or incompletely filled. I treated the foundationless frames as roughly (or carefully) as those with foundation during extraction – I uncap with a hot air gun and wind them up to full speed as quickly as practical.

That's blown it

That’s blown it …

 

The only real problem I had with foundationless frames in supers was getting unwanted brace comb in boxes where the frames were not vertically aligned with the box below. For example, an eleven frame brood box topped with an undrawn 9 or 10 frame foundationless super sometimes resulted in the bees trying to build brace comb between the frames. This problem was partially, though not completely, solved by mixing foundationless frames with a few frames containing full sheets of foundation. Next year I will get the comb drawn in a super filled with foundationless frames, and then remove a couple and space them further apart.

Brace comb

Brace comb …

Other than the infrequent building of brace comb, which can usually be avoided by careful frame spacing, I’ve only had two issues with foundationless frames that might be considered problems.

The first is the bees chewing through the monofilament supporting ‘wires’. I’ve been using 15 kg breaking strain cheapo mono picked up from eBay. If the frame isn’t drawn evenly (perhaps because the hive isn’t perfectly level) the exposed mono on one side of a frame is targeted by workers and sometimes nibbled through. In a frame with three transverse strands (i.e. a deep, or brood frame) this is usually the one closest to the bottom bar. This isn’t a major issue – it leaves a trailing strand which needs to be snipped off but the majority of the frame is usually drawn sufficiently well that it’s robust enough for the usual stresses and strains of inspections. In over 100 foundationless brood frames used this year, none have been unusable after the mono has been chewed through (which only happened on half a dozen). I’ve bought a big spool of 30 kg monofilament to use next year. At about 1p per metre it’s good value but may be a little less easy to work with.

Foundationless brood frame ...

Foundationless brood frame …

The second ‘problem’ is minor and depends upon your chosen method of swarm control. Colonies often draw out significantly more drone comb in foundationless frames than they do on standard foundation. It’s not unusual to have big slabs of drone comb on one or more of the outer frames of the brood nest. As a consequence, these colonies have lots more drones present throughout the season. Interestingly, I’ve not had increased problems with Varroa and deformed wing virus in these colonies. I generally use the Demaree method of swarm control, shifting the original brood box containing all the sealed brood above the queen excluder for a three week period.

Drone graveyard ...

Drone graveyard …

Consequently, drones emerging in the upper box cannot get out of the hive. If they are not periodically released – for example, during inspections, or by lifting the roof and crown board every few days – they sacrifice themselves struggling to get through the excluder. The standard inspection interval can uncover hundreds of dead and dying drones wedged half way throught the excluder. This is unpleasant, both for the beekeeper and the drones. Next year I’ll experiment with adding an upper entrance to allow the drones to escape – either by proving a thin shim of softwood underneath three sides of the upper box, or by providing a temporary hole through the side of the box (closed with a cork when not needed).

Finally, using a steam wax extractor on foundationless frames destroys much of the tension in the monofilament. They might still be usable – I’ve not tried – but it’s an easy job to replace it.

 

Foundationless frames

Beautiful

Beautiful

A discussion on the Scottish Beekeepers forums last year (and the price of foundation) prompted me to try foundationless frames. The general principle is that you build standard brood frames, reinforced with horizontal wires or fishing line, containing only a narrow starter strip of foundation. The bees build new comb, incorporating the strengthening wire or fishing line, without being constrained to the cell dimensions of the underlying foundation. The starter strip encourages them to build comb in the orientation you want. Without starter strips as guides it can be a bit of a free for all.

Freshly drawn comb

Freshly drawn comb

First impressions are very positive. During routine comb replacement or a Bailey comb change the frames have been drawn out very well, with beautiful near-white comb. The fishing line has been incorporated as intended and the comb appears reasonably robust – with the caveat that there have been no really hot days yet which can make the comb much softer. This shouldn’t be an issue once they’ve raised a couple of rounds of brood in it. The bees join the foundation to the side bars but often leave gaps at the bottom corners and/or along the bottom bars of the frames. They build a lot more drone comb, though the amount varies and reflects the strength of the colony. Very strong colonies seem to build much more drone comb, whereas nucs do not. I presume this is the bees regulating the colony composition as they want. The only problem I can foresee here is that drone brood removal will be less easy from one of these frames than by simply slicing off a lump of brace comb built on the bottom of a shallow frame.

During a recent Bailey comb change it was noticeable that the queen first started laying in newly drawn comb on a foundationless frame, rather than the flanking frames with commercial foundation.

Foundationless frame

Foundationless frame

I build the frames from second-quality parts (purchased at one of the beekeeping shows). Since these cost about £27 for 50 and you use ten times less foundation I estimate 50 prepared foundationless frames cost about 60p each  in comparison, using first quality frames and full sheets of foundation they cost a fraction under £2 each. These costs are based on our co-operative purchasing scheme prices for foundation which are already pretty good. Take care to inspect the second quality frames if you get a chance. The wood needs to be sound but the dreaded off-centre foundation grooves (which otherwise mess up beespace with full sheets of foundation) can be safely ignored.

Second quality frames

Second quality frames

I knocked a couple of 2″ nails into a block of wood to act a register points for the notch in the side bars. I then drill three roughly equally spaced 3mm holes through pairs of side bars. I’ve read elsewhere that the bottom wire/line support benefits from being closer to the bottom bars of the frame because – as explained above – the bees often do not completely seal the drawn comb to the base of the frame. Having assembled the frame in the conventional way I use 15kg fishing line secured with drawing pins or gimp pins rather than wire. There is at least one set of photos I’ve seen where the wire is relatively poorly incorporated into the drawn comb – I’ve not noticed this happening in any of the three dozen fishing line ‘wired’ frames I’ve used this spring.

Nailed

Nailed

Tie a simple overhand loop in the end of the line, place it over one pin at the ‘top’ of the frame, hammer it home then thread the free end of the line through the frame. To secure at the end I pull the line tight and wrap the line half a dozen times round a second drawing pin before hammering it home. To stop the line cutting deeply into the soft frame side bars you can use standard staples (just like you use for holding sheets of paper together … nothing too industrial) which can easily be pushed into the wood. Alternatively, I’ve used gimp pins knocked in next to the hole and hammered flat. Remember you only need a staple/pin one the side of the hole. The fishing line needs to be tight enough to provide rigidity; not so tight you can play a tune on it.

Lurid yellow 15kg mono ...

Lurid yellow 15kg mono …

A standard sheet of foundation is about 20.5cm deep. I cut this into 2cm strips, easily cutting through the wire with a Stanley knife. I secure it in place under the top bar in exactly the same way you would fit a full sheet of foundation. I’m pretty sure you could use an even thinner strip as a template for the bees to start from. Michael Bush describes simply breaking the wedge out of the top bar and nailing it back perpendicular. There are also various suggestionss about using a strip of melted wax or a wedge shaped top bar. I suspect that a thin strip of foundation is probably the easiest of the lot … it might be even more economic to use unwired super foundation.

Bait hive …

Bait hive …

I’ve used these foundationless frames one at a time between standard drawn frames of foundation – either in full colonies or nucs. They are readily drawn out and beautifully straight (though see the comments below on having a level hive). For Bailey comb changes I’ve added an upper brood box of alternating foundation and foundationless frames. There have been no problems with brace comb or the bees building comb in the wrong orientation. Finally, in my bait hives I’m using 9 foundationless frames flanked by two old tatty drawn frames. These have only been out a few days this year and have yet to be occupied.

STOP PRESS … they are now, and the foundationless frames worked a treat.

Drone cells

Drone cells

Bees build comb vertically. When drawing out foundation they have little choice but to follow the sheet. In contrast, if there is a significant slope (presumably front to back) and you arrange frames the ‘warm way’ there is a danger that the beautifully clean comb they draw out will not fit between frames using foundation, or that you’ll not be able to turn the comb around without messing up the beespace. If the hive does slope front to back – for example to help water drain out (why is it getting in? Perhaps try a Kewl floor) – you should be able to avoid this by arranging the frames the ‘cold way’.

Additional resources

Chris Slade has an excellent account of building and using foundationless frames on the recommended Beekeeping afloat blog.

Tom Bick started an interesting thread on foundationless beekeeping on the Beekeeping Forum.

(Inevitably … he covers most things) Michael Bush also has lots of information of foundationless frames at Bush Bees.