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Dave Black

Letter: The Nuptial Flight

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In 1901 Maurice Maeterlinck wrote a classic essay, [B]The Life of the Bee[/B]. While not intended to be a scientific work, it was grounded by the facts as they were known at the time. Even to day it is regarded as a masterpiece of prose and has inspired literature, theatre, and music. While it retains the sense of mystery and marvel we all enjoy, time has improved our grasp of the material things. In Chapter Five he writes of 'The Nuptial Flight', "...the manner in which the impregnation of the queen-bee comes to pass." [I]"Very few, I imagine, have profaned the secret of the queen-bee's wedding, which comes to pass in the infinite, radiant circles of a beautiful sky. But we are able to witness the hesitating departure of the bride-elect, and the murderous return of the bride.[/I] [I]However great her impatience, she will yet choose her day and her hour, and linger in the shadow of the portal till a marvellous morning fling open wide the nuptial spaces in the depths of the great azure vault. She loves the moment when drops of dew still moisten the leaves and the flowers, when the last fragrance of dying dawn still wrestles with burning day, like a maiden caught in the arms of a heavy warrior; when through the silence of approaching noon is heard, once and again, a transparent cry that has lingered from sunrise.[/I] [I]Then she appears on the threshold-in the midst of indifferent foragers, if she have left sisters in the hive; or surrounded by a delirious throng of workers, should it be impossible to fill her place. She starts her flight backwards, returns twice or thrice to the alighting-board, and then, having definitely fixed in her mind the exact situation and aspect of the kingdom she has never yet seen from without, she departs like an arrow to the zenith of the blue. She soars to a height, a luminous zone, that other bees attain at no period of their life. Far away, caressing their idleness in the midst of the flowers, the males have beheld the apparition, have breathed the magnetic perfume that spreads from group to group, till every apiary near is instinct with it. Immediately crowds collect and follow her into the sea of gladness, whose limpid boundaries ever recede. She, drunk with her wings, obeying the magnificent law of the race that chooses her lover, and enacts that the strongest alone shall attain her in the solitude of the ether, she rises sill; and, for the first time in her life, the blue morning air rushes into her stigmata, singing its song, like the blood of heaven, in the myriad tubes of the tracheal sacs, nourished on space, that fill the centre of her body. She rises still. A region must be found unhaunted by birds, that else might profane the mystery. She rises still; and already the ill-assorted troop below are dwindling and falling asunder. The feeble, infirm, the aged, unwelcome, ill fed, who have flown from inactive or impoverished cities — these renounce the pursuit and disappear in the void. Only a small, indefatigable cluster remain, suspended in infinite opal. She summons her wings for one final effort; and now the chosen of incomprehensible forces has reached her, has seized her, and, bounding aloft with united impetus, the ascending spiral of their intertwined flight whirls for one second in the hostile madness of love."[/I] A hundred years ago, not all the remarkable secrets had been discovered, and while Maeterlinck understood the value of "cross fertilization", the fact that a queen will mate with several males eluded him. The longest flight duration a queen can manage is about 30 minutes, as this is limited by the amount of honey she can carry to power the flight. Leaving a secure shelter to mate with males several kilometres away, dodging predators, and safely navigating the weather systems and terrain back to a point a few centimetres wide, is a risky enterprise. On average the queen will fly a couple of kilometres, but a maximum of 5km has been observed. Ten to twenty percent of queens never return. It’s not just a personal risk either. Once the old queen has left no eggs are being laid. By the time the virgin emerges, gathers strength, and flies to mate, there will be no possibility of young larvae being fed to replace her should she fail. If she fails, the colony dies. If mating is incomplete and the sperm stored can’t match the egg production of her ovarioles, at some point she will start laying unfertilised eggs – she will become a drone-layer. Eventually, the colony dies. The big question is, how does a queen balance the risk of flying out to mate against the need to find multiple mates; is she able to decide ‘enough is enough’, and how many does she think is ‘enough? Why mate with several males in the first place? Drones face a similar dilemma. Four or five days after emergence they take their first orientation flights, and after about another ten days their first mating flights. Drones are sexually mature after 16 days. To maximise their chance of mating they have to be in the right place at the right time, and the ‘right’ place is a Drone Congregation Area (DCA), typically around 5km to 7km from their hive. Drones fly to (DCAs) on warm sunny days after midday. They will make several flights lasting 30 minutes or so, returning to feed in between sorties. Flying to and from a DCA is risky and time wasted, as is the fuel providing the energy for the flight. That is not to say drones will just fly to the one nearest home, but that is one possibility. For a drone the compromise must be between the energy it takes to travel versus the probability of mating successfully following arrival. As drones from the same hive can be found in many DCAs distance can’t be the sole factor. While we know very little about how drones select (or find) a DCA we suspect they use topographical features (horizon shape is a plausible feature too), and we know they visit more than one, so it can’t be all about energy efficiency. We don’t know how a queen finds a DCA but I’ll bet she has a different method, otherwise she’d end up at the same DCA as drones from her own hive. We know (by following genetic makers) very few matings occur in the vicinity of the queen’s colony. A gathering of drones within an area, and consequently the flight of a queen to that area, will have the effect of reducing the risk and effort associated with finding mates in a multiple-mating system. I’m sure you can imagine your own human parallel! Forty metres up in the air, DCAs are quite tricky to study. At first, the best you could do was raise a balloon or kite from underneath with pheromone lures or traps, or fly a tethered queen into the melee and watch what happened. In the late ’60s it became possible to use portable radar units to look at some physical attributes, and now genetic techniques can tell exactly who is visiting, where they come from, and how successful they are. Sophisticated film and photography have allowed a close-up view of the behaviour in the mating ‘comet’. DCAs persist from year to year, probably as long as the landscape remains unaltered; some have been observed for more than 50 years. As long as the weather is favourable, each day, regardless of whether there are queens present, drones will gather in these areas and wait, flying slowly in large looping circles and waiting for queens to fly into the vicinity. Curiously, outside these areas, the drone’s response to the queen’s pheromones is limited, and a queen that flies out of the area is not pursued. DCAs are (presumably) all different, but some researchers have estimated the number of colonies contributing drones to an area, and how many drones might visit. In one studied near Oberursel in Germany almost 240 colonies had drones in the DCA. In another study, carried out over five years, the number of individual drones visiting an area each day was, on average, 11,750. Mark Winston has reported up to 25,000 a day. A DCA will measure something like 30m high (starting 10m up) and cover an area as much as 300sqm, but the shape and volume of the DCA will vary with the wind strength and direction. Given these kind of numbers, the drone density, will still only be a couple of drones per cubic metre. Queen mating is an extraordinarily transitory event. When a queen flies into a DCA a ‘comet’ of around 30 drones will form, perhaps several meters long, the drones flying behind and slightly below her. The flight speed of drones, in these circumstances, is limited by the speed the queens fly at. The time a drone spends in this comet, successful or not, has been measured to be between 0.7 and 1.7 seconds, flying at about 3 metres per second. The only form of ‘competition’ between drones is in the jockeying for the best (closest) mating position around 8 to 12 centimetres behind, during which drones can accelerate to 5 metres per second. Presumably a drone can tell very quickly if his position is hopeless and drops out of the race to be replaced by another, or to re-enter in a more favourable position. There is no evidence of a mate ‘choice’ by queens. Copulation for a successful drone only last a couple of seconds, but the ‘mating sign’ he leaves flags the queen and makes it easier for a successive suitor. It has been assumed for a long time that the reproductive success of a colony’s male line was determined simply by the number of drones produced. Certainly weak colonies tend to produce few, if any, drones, and large colonies can afford to make a considerable investment in drone production. This ‘male fitness’ of colonies has been re-examined in recent years. Genetic analysis, and studying colonies in a closed mating environment (like off-shore islands,) has shown numerical superiority is not a particularly significant factor. Even when colonies have been equalised for drone numbers, size, queen line, and so on, a remarkable difference exists between colonies in their ability both to mate with queens as drones and in the successful ability, post-mating, of their semen to sire off-spring. Varroa too has a hand in this, as the effect of the parasite reduces body size (and so sperm volume), decreases flight times, and causes the death of many drones before they reach the point of sexual maturity. Drones infested by varroa are less likely to make it to a DCA and lack the physical ability to make a success of their time there. It is entirely possible that at any given time colonies adopt one of two strategies to try and achieve reproductive success. They can ‘invest’ in queens, and release swarms (which also requires a large investment in accompanying workers), or they can produce effective drones. At the heart of all this complexity is a very simple thing. Genetic diversity is the most important characteristic of a honey bee colony to think about if we want to understand how it survives in its environment. It is diversity that allows it to survive disease, to respond efficiently to food sources, and to exploit new homes and landscapes. It is so fundamental that, at the extreme, a lack of diversity will result in the colony dying. With only one female, diversity is introduced through the male line. The necessity for a diverse choice of mates is even a component of the determination of gender itself. Gender in honey bees is determined by one gene that appears in as many as 17 ‘versions’. Female bees are ‘heterozygous’ for the gene, which just means they have two different copies of the gene in the same place on their chromosome (with two you hear them called ‘diploid’). There are two types of male bees, one that is ‘homozygous’ (two of the same copy of the gene) or ‘hemizygous’, with one copy (a half) because the individual is haploid. The latter is a normal male, the former, a ‘diploid’ male, is sterile. Clearly a sterile male isn’t much use and you hardly ever see them because the worker bees destroy them. We can suppose therefore that one reason honey bee mating has evolved as it has is to reduce the chance of two of the same gene copies (we call them ‘alleles’) coming together. The greater the variety of alleles the better. As honey bee males only have one, that means the female must mate with a variety of males, and unrelated males at that, to reduce or eliminate the production of homozygous eggs, and so sterile males. The boffins calculate that the optimum number is between six and ten. Females must, to use the biological term, be ‘polyandrous’ (from the Greek ‘poly – many; ‘andros’ –men). In fact honey bees are given as an example of ‘extreme’ polyandry, and typically mate with ten to twenty males. Slightly more than half of queens make two or more mating flights. This is not all good news. As any female will tell you, forming a relationship with lots of males at the same time is fraught with problems. Explaining quite why, in practice, honey bee queens routinely mate with more males than is strictly necessary (assuming the sums are right), or why sometimes ‘extreme’ means queens have been observed to mate with nearly fifty males, is a challenge. It may that there is no reason, they just happen to. Many social insects exhibit polyandry, so it isn’t a question specific to bees. Polyandry could be a ‘good’ thing (i.e. contribute to colony ‘fitness’) because the workforce is more adaptable, the response to environment ‘cues’ is more progressive, diseases cannot strike every individual at once, and because of genetic mechanisms such as the determination of gender. Honey bees are the easiest example of polyandry to study, and by using artificial insemination it is possible to investigate the significance of the various ‘benefits’ offered to explain polyandry, and in bees, keeping a high number of sex alleles is thought to be the most significant. Nevertheless, there comes a point at which there is no additional advantage in having more mates; the Law of Diminishing Returns applies. The jury is currently out on the question of whether queens can judge ‘enough is enough’; it appears that they can ‘count’ the number of mates and/or asses the number of spermatozoa ‘on the wing’ (for example, the queen will be heavier), but that they may not do it very well. Perhaps they already have enough to think about.

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Thank you Dave, as usual with your writings, very informative, keep up the good work.

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Yes. I agree with Fieldbee. Another well written article and the opening prose is wonderful. Many thanks.

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[quote="Chris Valentine, post: 20727, member: 53"]Good read ,but have to read it again to take it all in[/quote] Hence .pdf :)

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[quote="Dave Black, post: 20796, member: 219"]Hence .pdf :)[/quote] Yes and easier to take to be for light reading rather than balancing the Laptop on my knees.

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[quote="Trevor Gillbanks, post: 20827, member: 72"]Yes and easier to take to be for light reading rather than balancing the Laptop on my knees.[/quote] Make sure it is on your knees and not higher. Heard on the radio laptops are cooking the male reproductive cells. Just another form of contraception.

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[quote="P K Tan, post: 20920, member: 367"]Make sure it is on your knees and not higher. Heard on the radio laptops are cooking the male reproductive cells. Just another form of contraception.[/quote] At my age it would not matter anymore.:thumbdown:

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@Dave Black , have you read about the work being done by Keith Delaplane in the UK regarding the benefits of extreme polyandry?

 

All of this is from memory, but I watched a lecture of his on youtube and he talked about his experiences breeding bees. Basically he had tried to breed the "perfect bee" in a closed breeding programme and in his opinion failed. I can't remember the exact trade offs but as an example, when he made gains in fecundity, he made losses in docility. When he made gains in honey production, he lost fecundity. When he made gains in VSH behaviour, he made losses in honey production, etc. etc.

 

He then outlined where polyandry in social insects comes from, and it's benefits. I'm quite curious where the figure of 6 - 10 mates as the "optimum" number came from? The table I remember seeing from the lecture showed that 82% or so of the possible genetic benefit that polyandry was reached by 6 mates, by 20 mates it was well over 90%. I assume the optimum is given as 6 mates in naturally mated situation where the risks of predation, etc. outweigh the benefit once 80%+ fitness has been reached? Delaplane seemed to indicate that there was no downside to increased mate numbers when the threats of natural mating are removed (however my other reading has indicated that STDs may be an increased risk with increased mates).

 

Delaplane had done field work in the UK with Queens which had been AI's with the semen of 60 drones, and initial results showed marked increases in fecundity, honey production and even reduced varroa count.

 

In the lecture I watched he strongly implied that a way forward, that may provide real results for Queen Breeders and therefore Beekeepers, was for lines of a single sub-species to be breed for single traits (in the most genetic diverse way possible) for say; honey production, VSH behaviour, docility, hygienic behaviour, etc. and then drones taken from the 'best' colonies and the semen of 100+ drones pooled for use in AI, and that this may result in Queens that are remarkable and worth the extra cost the method would require.

 

Thoughts?

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@Jezza I think I have the paper in my files, but I don't remember the last bit about the way forward.

I'm afraid I have to delay my thinking as I working long days at the moment. :) Until later...

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An irony of any breeding program for any productive subject can be that eventually the realisation is made that the long lost original material wasn't so bad afterall.

 

My opinion based on experience with a couple of racing animal species

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@Dave Black , please note that the way forward was my inference from the summary Delaplane gave at the end of his lecture. Is his paper regarding his polyandry field results online? I would like to read it.

 

An irony of any breeding program for any productive subject can be that eventually the realisation is made that the long lost original material wasn't so bad afterall.

 

My opinion based on experience with a couple of racing animal species

 

I think that is what appeals to me about this potential breeding method. Rather than intensive selection for certain traits, and all the issues and homozygousity that goes with it, the bees naturally tendency (and the advantage it provides) towards extreme polyandry is exploited with only a minimal filtering process beforehand. Unfortunately I don't have the in depth knowledge or experience required to develop the idea further at the moment.

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