Brood Rearing in the Winter Cluster
By Bernard Mobus, N.D.B.
By kind permission of the ABJ, first published July 1988.
Part 1 of two.
Winter is an annual event, and the cold season will be here again before we know it.
Wintering losses of honey bee colonies are becoming more frequent and serious now
since varroa is infecting colonies worldwide. Beekeeping is in retreat, especially among amateurs and hobbyists. And, we must admit that even a low level of infection in spring can have a disastrous effect on the colony towards the late summer. Following the first anti-varroa treatment in spring. a small number of surviving mites increases steadily throughout summer when no form of control can be administered effectively. When autumn comes near. and bees prepare to face the coming winter by rearing a last batch of brood maybe thousands of mother mites are entering the cells and they, and their progeny, will draw the life-blood of the very bees which should become winterbees :
° the very bees pre-programmed to store additional reserves of protein and fats for winter – in order to
become the very bees which should survive the coldest part of winter in a partial dormancy. – and survive to be. .
the very bees which should rear the first batch of brood the following spring and carry on the species.
Autumn treatment against varroa, when all brood has emerged and after the honey harvest has been removed, may come too late; all emerging bees are damaged bees are physiologically unfit to face the cold and are prone to disease. Many of them die, too early in life. thus weakening cluster strength and reducing its chances of survival.
ln order to improve our colonies’ chances of successful wintering. we must first Ieam all there is to leam about Varroa and its control. But we also must learn more about wintering and about the winter cluster. Of course, books are full of the traditional version, and the old recommendations also tell us that one should leave the wintering colonies alone, and never look into hives or interfere with the bees – or hives. But finding out how things work is an old human failing, and over the years beekeepers and scientists have poked mercury thermometers into
the cluster, have gassed whole colonies before taking the hive apart and examining combs minutely. Recently, they also have taken the easy way out and have introduced lots of thermocouplcs into hives in order to take regular readings of the temperatures of the cluster and of its surroundings and have recorded them on a daily, hourly. or more frequent basis. The scientists then made their computers analyze the readings and produce pretty graphs and isothermal contour maps of the winter cluster – which they never saw! Pretty, but is that the whole story?
True, it is best to leave bees alone once the colonies are well fed and safe from the wet and the driving snow. Yet in the l950s, a Dr. Jeffree did try to discover what is going on in the winter cluster, and he examined about 360 colonies over a period of I0 years while he was at Aberdeen. Scotland. He tells us that it is all right to look into hives. provided the air temperatures rise high enough to permit cleansing flights and allow bees to retum
home safely afterwards (Jeffree. E.P.1956). He discovered patches of brood at any time of the winter period. although the size and their occurrence appeared to increase towards spring. Furthemtore, he could not relate their occurrence to climatic conditions affecting the whole of the apiary. Most hives were inspected once only in each winter. but among the seven colonies which he examined repeatedly weather permitting – he found in two of
them evidence of stops and starts of brood rearing.
All right. the winters in the north of Scotland can never match those of the northern states and of the Canadian
provinces. but wintering in a cluster relies on inherited patterns of social (and individual) behavior which uarantees survival, and the basic principles reside in the genes of all bees of the European races of Apis mellifera L. Variations in temperatures are only a matter of degrees, not of principles. And, although the two winters were exceptional. sometimes the winters can also be bitter and prolonged in Scotland.
Dr. Jeffree’s work, as well as that of many other scientists, was of great interest to me after l had discovered brood rearing in my hives in Lincolnshire one winter. Pondering over the reasons behind such an activity which. of course, could cost the lives of colonies through starvation or nosema disease. the search for an answer became a veritable compulsion. l took part in wintering surveys of food consumption, and was surprised at the varia-
tion in food consumption between colonies. After that, I started to examine my own colonies whenever l could.
When I was appointed to the Advisory Post at the College of Agriculture of the North of Scotland at Aberdeen, my investigations into the problem of brood rearing in the hive-locked winter cluster were intensified. During the first two winters, nearly all colonies in the Craibstone apiary (and my own) were subjected to regular inspections (weather permitting), and some of the colonies took part in other experiments which included the caging of queens (with access by workers). as well as the formation of ‘super colonies’ by uniting strong colonies to form one unit.
ln this part we will first consider the work of the examinations, and the Tables I and 2 give a representation of my findings in the winters of 1974/75 and 1975/76. The two winters gave me numerous chances for examinations, with mild spells luckily occurring roughly (and randomlyl) every three – four weeks. So as to avoid artificial engorgement, the hives were opened without smoke and the bees settled quickly without further aggression
within minutes after closing up. Although it must be admitted that – possibly – more bees used the disturbance for a chance of an additional cleansing flight – and my protective clothing was needed for another protective reason!
Whenever a patch of brood was discovered, it was not only measured, but also minutely examined for the presence of eggs, larvae or pupae. and their presence was registered for every face of comb (Tables I and 2).
Explanations for the study of the tables are: Each field is divided into three: eggs, larvae, pupae; as indicated below the date (e; l; p). Each line corresponds to one frame, and a slash (I) represents the mid-rib of that comb. A plus sign (+I+) on both sides of the slash means that eggs, larvae or pupae were present on both faces. Sometimes one look was enough to see that the older, larger larvae were missing, and so particular attention was paid to any irregularity in the pattern of larval age. Whenever only eggs – and no larvae – were found, or at other times only one-day, two-day or three-day-old larvae were seen in the depth of cells, this was recorded separately. This is represented as a figure 1, 2, or 3 instead of the plus sign which indicates the presence of larvae of all ages.
Of course, beekeepers immediately recognize that here the queen had stopped laying for a while and that she had just started again after a ‘brood stop’ had occurred. Some colonies showed two or three of these stops, and they are identified with exclamation marks in the appropriate column. In one colony the few remaining capped cells looked suspicious and their contents were removed. They were dead, fully developed pupae, but the imagoes looked shrivelled. They were mummies only and showed no sign of AFB or EFB. An asterisk, (I*) not a cross, indicates these findings.
The tables show that some brood could be found in some colonies during any of the winter months; even November and December were not without such activity. True, the number of colonies starting to rear brood and the size of the brood patches increased towards the end of the winter period. But the number of brood stops
(and starts) also became more numerous towards spring. The sum of the brood areas discovered (in centimeters, and not adjusted to account for longer of intervals between inspections), is recorded at the right of the tables, and it shows wide variation from I47 cm’ to 2730 cm‘- all in the same apiary. Allowing for a cell density of 4 worker cells to the cm’, the number of bees born during ‘dormancy‘ ranged from a low 588 to l0,920 bees. The last figure represents a veritable and generous 2 lb. package!
The pattems of egg laying also are of passing interest. In some colonies the small patches of brood were on opposite faces of adjacent combs ~ and the queen did not have to leave the center of the cluster, while in Col. 2 (Table 2) the queen had to move over into the neighboring passage to lay her eggs on the other face of the
same frame-a colony with too small a cluster to support a larger brood nest? No, a spring examination showed that the two colonies were firing on all cylinders once March had arrived and some foraging activity had recommenced.
Only one queen died during the winter examinations of normal colonies (Col. No. 24; Table 2). We have always been warned about the danger that bees may ‘ball’ their queens when interfering at wrong times, but the records show that in this case pupae were still emerging 30 days after the last inspection. ‘l`his implies that eggs were laid for at least one more week after the last examination, and that the queen must have died from ‘natural
causes‘, maybe old age.
lt is just these details of the careful inspections which made the work so important. Although brood rearing in win-
ter has been known to occur for a long time, sometimes by accident, no other work has supplied the clear evidence that brood rearing stops and starts occur so frequently and are probably an important part of winter brooding. Even hundreds of thermocouples registering every five minutes cannot show up the cessation of egg laying nor its re-initiation. After all, brood rearing is an on-going process and lasts three weeks (possibly longer in a winter clusterl). so brood nest temperatures will be maintained at the high level of 35°C as long as living brood is present (unless brood dies for some reason). Yes. in later years we also did a lot of recording of hive and cluster temperatures, but that work never provided us with the same insight into cluster behaviour as our direct inspections of winter clusters.
Yet it must be the initiation and cessation of egg laying by the queen which should provide a clue to brood rearing in mid-winter. Even among bees the old saying applies: “Every baby costs its mother a tooth.” So we do need an explanation for the seemingly ‘wasteful’ production of food and for the increased wear and tear this brings for the ‘dormant’ bees. but which are now sacrificing ‘life and limb’ important protein reserves to raise young bees. Bees are thus laying themselves wide open to early death and nosema disease. Furthemiore. we also need an expla-
nation forthe need of such ‘wastefully‘ high cluster temperatures – which could lead to starvation of the colony as a whole.
The last sentence is not scaremongering. Hives had been weighed before winter started, just when flying had stopped. When milder weather and flight for water, for early pollen and nectar was becoming possible again on a regular basis, we called it quits and weighed all hives once more. A superficial examination of the listings showed a relationship, and when the sum of the brood areas and food consumption were statistically evaluated, a very high correlation: r = 0.92 was obtained for the two winters and the 33 hives. Further statistical analysis even sup-
plied the following regression equation 2 Food consumption = 4.1818 kg + 0.000375 (kg) per cm’ of brood.
Again, these values apply for the increase in food consumption – demanded by brood rearing over and above a basic minimum – only in the Craibstone apiary just outside Aberdeen over the two winters. But in principle they will stand for all true wintering in any climate. The results are so clear and significant – in spite of the individual patterns and areas of brood rearing and the greatly varying food consumption, that we can say the following:
Wintering is a cluster-specifc experience, and any brood rearing in mid-winter costs additional energy over and above the basic energy requirements of a non-brooding colony.
Of course, we must never forget that winter brooding can also pemiit Varroa to ‘rear brood’ in mid-winter, and that many more young and strong Varroa mites will have a head start once brood rearing commences in eamest. So why do bees rear brood in mid-winter? How can we stop it? Furthermore: Should we try to prevent brood rearing – and how?
Well, some other experiments do seem to answer the questions. at least the last question. During both winters some queens were held in the center of the cluster in a small cage of excluder material in order to prevent them from laying eggs (while still giving bees ready access). Most of these colonies developed dysentery within three – four weeks and grew weak and weaker and hardly one stock in this group recovered when the queen was released in spring. ln only one case did everything tum out all right after wards. The queen was caged when brood rearing had started and before any cells had been sealed. When, six weeks later. signs of dysentery were seen, she was released from her prison. Four weeks later, at the first inspection of spring, there were 822 cm’ (about 3250 cells) of brood on two frames and no more dysentery. The records show the remark made at that time: “population greatly reduced”. (None of these colonies appear in the tables, and none were included in the calculations of statistical analysis.). So it seems that – sometimes – NOT rearing brood is even more stressful than doing so!
‘Super colonies’ were created during the second winter period. Such colonies never reared any brood. ‘l`hey had been formed as an additional experiment after reading Dr. .leffree`s other paper in which he disproved the age-old advice that “the best packing for bees are more bees”. He had found in his work on the influence of colony size on the rate of population losses, that the weak stocks, as well as the very strong colonies, lost more bees than what he called ‘ nominal sized‘ colonies. lt was for that reason that I decided to sacrifice four strong stocks in autumn and to unite. in each case, two of them by the newspaper metl1od after removing one queen. In both cases uniting went off peaceably. and all seemed well. Bees were frequently flying from these ‘super colonies’ and their flight was fast and direct – not to rob a weak stock. but to a source of water.
After a longer spell ol` cold. the weather relented again to permit cleansing flights and inspections. Both ‘super colonies’ had massive. disastrous losses, and bees were clinging to the hive sides, to hive stands, to grass blades as if the ‘Isle of Wight’ disease (tracheal mites) had struck another blow. But trachea were clean and healthy, and no Nosema was found. Bee samples taken came to life again once they were in the wamth of
the laboratory. With an idea fomiing in one`s mind. the bodies were then weighed individually before bowels and honey stomach (with contents) were removed for further investigation. These produced the following results.
When compared with samples taken from standard and dyscntcric colonies (in that order). (See Table 3)
The bees from the ‘super colonies’ had no excuse to fly on a cleansing flight.
In fact, the bees were dehydrated and had flown en masse for reason of dire thirst! And, coming from a warm cluster without having to contribute to heat generation, they chilled by the thousands before reaching their goal: water.
Biidel, A. (1948) Die Temperatur in der
Beute. Imkeijieund I0 ; 89
Farrar, C.L. (1963) The Overwintering of
productive Colonies. The Hive and
the Honey Bee, Roy Grout (Editor),
Dadant&Son, Hamilton. lll..U.S.A.
Available all summer and fall
Free, ,].B. (1968) Engorgement of honey
by worker honeybees when a colony is
smoked. .l.Apic. Research 7(5) : |35 ;
Jeffree, E.P. (1956) Winter brood and
pollen in honeybee colonies. Insect
sociaux 3: 416 – 421
Jeffree E.P. & Allen, M.D. (1956) The
inllucnce of colony size and nosema
Rethinking Our Ideas
About the Winter Cluster
by Bernard Mobus
In the last article I wrote (July, 1998 ABJ) about the observations made while examining colonies over a period of two winters in northern Scotland. They had produced the surprising fact that egg laying by the queen within the winter cluster is very much an ON/OF F affair; even though ‘brood rearing’ would be registered as ‘con-
tinuous business’ by any number of thermocouples inserted in the center of the cluster: The examinations showed that brood rearing in the hive-locked winter cluster is more complicated than we had thought, and that the initiation and cessation of egg laying , rather than brood rearing, itsem has to be investigated with fresh insight.
But before passing on to theoretical stuff I want to report on a further experiment made in the year following above the examinations. ln the Craibstone Apiary was a small hut with self-registering scales’ and during the winter of 1976/77 we placed one colony in a Langstroth hive on its platform. Under its floor board we had put a sheet of extruded polystyrene (Roofmate) of 30 mm thickness. From another sheet of expanded polystyrene (50 mm thick) we constructed a box which we could place over the hive so that it would be encased all around in insulating material. An opening of 15 mm was left as an entrance, and this opening coincided with that of the hive itself. It also was at the same level as the flight board of the hut. When we lifted the outer casing and put it upright over the crown board, the hive was left ‘in the cold’ (apart from the sheet under the floor board), although the total weight had not changed.
The self-registering scale was very accurate and its sensitivity was adjusted so as to read 50 g between the lines on the chart. The charts were changed weekly on Mondays at 9 a.m., and the consumption for the week was recorded. Measurements began with the onset of ‘winter’ and stopped when we could say ‘lt’s Spring!’.
That winter we had no chances to examine colonies for winter brood and there were some long, cold periods. during the whole of the mid-winter period there were only three chances of cleansing flights, two of which occurred on consecutive days. Each time many bees were ‘lost’ from the heavily insulated hive. They were found apparently chilled on the ground, on grass blades and clinging to the side of the weighing hut as if the `lsIe of Wight‘ disease (acarine) had struck again.
No other stocks showed such losses, and most bees from other hives retumed home after a cleansing flight. The ‘chilled’ bees showed no acanne or Nosema disease. The sharp drop in weight on these days was taken as due to loss of bees, (after an average daily consumption had been allowed for) and we had to ignore any loss in
weight from defecation-or any gain from water collection.
The table makes it clear that the insulation slashed the daily food consumption of the colony by more than half. On the other hand, even the weighing hut itself must have had a protective, insulating effect because, if we take the daily loss of weight ‘in the cold’ and apply it for the whole period of 26 days, then we would still have had the surprisingly low food consumption of 4.17 kg (9.2 lb) of honey.
Checking with last month`s article, we find that this figure agrees with the result of the regression equation for causal relationship established for normal colonies rearing no brood (in that apiary and climate). Although no thermocouples had been used. and no examinations could be made that winter, the low food consumption can be taken as proof that no brood rearing took place in that stock during the winter period. lndeed, taking the strength of a ‘normal` winter colony as between l0,000 to 15,000 bees, the average consumption of
honey per bee and per day under insulated conditions was so minute (1.0-1.5 mg/day/bee) as to make us wonder if the bees lived indeed on love and altruism, rather than on honey. The production of
brood, even of a single larva of about 100 mg weight in 5 days, would have been impossible on that ration! Leaving for the moment the implied suggestion that colonies with a low food consumption are probably not rearing any brood in the depth of winter, the disturbingly heavy losses of bee life from ‘super colonies’ and those surrounded by exceptionally thick insulation in a mild, maritime climate must make us take a new look at the often repeated advice ‘that the best packing for bees are more bees’. Dr.Jeffree investigated this fairly common sense advice with a critical eye.
Extended and thorough investigation of colony sizes before and after winter made him come to a different conclusion. His findings surprised him and he announced that there is an ‘optimum size’ of winter cluster, and that colonies with smaller-or larger-populations will suffer greater losses than the stocks which could be called normal, standard, or optimum for that climatic zone.
So it is time that we clear up old ideas of the winter cluster and introduce a new cluster model based on biological
investigations rather than on traditional theories which have only gained credence by being repeated frequently and slavishly-in most books. ln order to present this traditional working model of the winter cluster, we can do little better than quote here from one of the most popular and standard books on beekeeping. In a revised 1975 edition of the book The Hive and the Honey Bee, Professor Furgala gives us the classical point of view:
“When forming a cluster, bees on the surface establish an insulating shell which varies in thickness from 25-75
mm. Bees enter the empty cells within the area of the food reserves embodying these cells, forming an integral part of the insulating shell. As the external temperature rises above 7″C ( 45°F ) the cluster expands. As the temperature drops below 7″C (45’F) the cluster contracts, reducing the surface from which heat energy is radiated. Since bees use their honey reserves most efficiently at 7″C (45″F) (Betts, 1943), they do not con-
sume as much of their stores at low temperatures as might be expected. “The bees within the cluster are
much less compact and generate heat through metabolic processes (Phillips and Demuth, 1914; Farrar, 1963). The heat produced within the cluster is conducted to the surface of the cluster. Sufficient heat is generated to equal the heat radiated from the surface at approx imately 7″C (45″F) (Farrar, 1952). “The expansion and contraction of the cluster, therefore, is the principal mechanism used by bees to sustain a favorable environment. This phenomenon will function as long as the cluster maintains firm contact with its food reserves. “
This version of the traditional idea of the winter cluster can be found in most modem bee books, and the old treasured ones are even clearer in their opinion that the bees in the cold form an insulating shell to keep the center of the cluster warm and protected, with the bees in the center busily occupied in converting honey into heat ‘by metabolic processes‘.
This is conducted (through insulation!) outward to keep the poor shivering sisters alive. Of course, this model grows more and more improbable as external temperatures drop and the quality of the insulation of the shell thickens with improved conductivity to keep the outer most bees alive. Anyone who has studied physics and is not a beekeepermust be astounded to hear of an insulating conductivity or conductive insulation His findings surprised him and he announced that there is an ‘optimum size’ of winter cluster, and that colonies with smaller or larger populations will suffer greater losses than the stocks which could be called normal, standard, or optimum for that climatic zone, with such marvelously variable properties! Of course, any cluster model which
credited the honey bee with altruistic, even miraculous behavior suited the beekeeper of the past and found ready ears, but all such chapters need revision in the light of modem research. Indeed, as far as the bees’ cluster is concemed, careful research has shown that we all will have to make a Copemican about-tum.
lt is not possible to quote every recent work on the subject, and so I will confine my arguments to the most impor-
tant research onthe subject of the wintering bee’s metabolism. After a period of letting individual bees ‘settle down’ in minute cages, two researchers (Altmann and Gontarski) held the bees immobile for further 30 minutes at precisely maintained temperatures (See Fig. 4).
Their metabolic efforts were established by the absorption of the carbon dioxide produced during the period and, at the same time, their loss of water through evaporation was measured. Each test was repeated many times with fresh ‘winter’ bees over the whole range of temperatures which can be found within the cluster.
The results, as shown in the graph, prove conclusively that bees in the warmth used very little food, and therefore produced very little heat energy. The bees were at rest, their metabolism had been switched to ‘idling’, their energy producing ‘motor’ was just ‘ticking over’. At the same time, these bees were found to be evaporating more water from their bodies than they were producing as a ‘waste product’ through their metabolic conversion of honey sugars.
On the other hand, the bees which were experimentally exposed to the colder temperatures of the outer shell, the bees held in cages at variable temperatures down to l0°C, were actually the producers of the most carbon dioxide and therefore the most active converters of honey sugars. Well, they were not far away from the cells of stored honey and did not have to travel far for a fill-up when this was needed. Of course, and this goes without saying, they also produced the largest amount of ‘waste’ water which, applying plain chemistry, amounts to 0.6 g water forevery l g of glucose convened into heat energy through oxidation. The table shows that the bees consumed less and less food, the nearer they ‘lived’ to the warm centre.
On the other hand, the bees held at temperatures found further away from the center, consumed more and more honey with each drop in temperatures. And, even under the conditions of the experiment. they were slowly building up a water surplus, although the quantities of water evaporated was fairly even between 20°C and 30°C. Evaporation increased by leaps and bounds at brood nest temperatures and slightly above. ln short. we must state the following:
When clustering is brought about by the onset of colder weather, each bee in the cluster will generate heat in direct proportion to its heat loss which is in inverse proportion to its own temperature experience. Bees in the warmth of the central region have a lower metabolic rate and will produce less water than they are evaporating here. Bees of the outer shell will generate more heat energy, will consume more honey and will, consequently, accumulate more metabolic water than they can evaporate in this colder region.
A similar experiment made by Roth in France fully confirms the above findings. He, too, investigated the conversion of sugars into heat energy by measuring the production of carbon dioxide at various temperatures, although no measurements were made to investigate water loss through evaporation. Roth, quoted by Chauvin, found that the metabolic rate of heat production was at its highest at l2.5°C. Yet the graph shows that at 10°C the individual values obtained were so variable, that one can not even state that heat generation breaks down entirely at this precise point.
When he repeated the tests with groups of 25 bees, he found that the contact between bees immediately reduced the individual effort, but the graph for groups of bees still followed the curve established for individual bees, albeit at a lower level.
But even Roth’s results agree with the above findings: The colder the bee, the greater its personal effort to survive by increasing its own rate of heat generation, and that the density of clustering, the short-range social contact, serves to pool the personal heat resources as well as to benefit from the nearest neighbors. The bees in the warm center of the cluster, on the other hand, are not even clustered for closer contact; they are making the least
effort and contribute little towards the common good-warmth.
Now we must tum to the next point raised by the results of Altmann and Gontarki`s experiments, and this may be,
for beekeepers, the most difficult pill to swallow. The bees in the center with the lowest food consumption were found to be losing more water vapor than they were actually producing through oxidation of sugars. On the other hand, the bees in the cold outer shell are convening a lot of sugar into heat energy, and cannot help but produce a lot of metabolic water at the same time. Out in the cold, they evaporate little moisture, and a surplus must build up
in tissues, in the bowel system (via Malpighian tubules) and must finally accumulate in the rectum.
This brings us to finding a solution (which, no doubt, the bees had discovered and used over, thousands of years of living in cold climates). Under normal cluster conditions bees from the center tend to drift to the outer shell for a ‘metabolic drink’ by increasing their rate of heat production and by lowering evaporative pressures. Moving into the center in order to ‘dry out’ is the solution for bees of the outer shell, and slow movements in and out of the cluster center are probably motivated by the driving force exerted by thirst or water surplus, rather than any thoughts of letting sister bees warm their feet! The selfish, survival-orientated exchange of bees between layers is biolog-
ically sounder than the altruistic motivation of the past.
Of course, such an ideal solution for all personal ‘water problems’ works best when the size of the winter cluster is commensurate with that population which can form Dr. Jeffree’s ‘optimum winter cluster’for its climate. His investigations showed that any large deviation from the ideal size-up or down-was ‘punished‘ by Nature with occasionally heavy losses of bee life.
Our numerous experiments with ‘super colonies’-and the one in the weighing hut had shown, that when there are too many bees in a hive, or when the hive is too insulated and too warm for a mild climate, thirst-crazy bees were driven out to fly at the slightest excuse; not to gambol in the sunshine, but to collect water. But, coming from the warmth with out having contributed towards its maintenance, they quickly chilled before reaching it.
Colonies smaller than optimum size and we all had our doubts about some stocks, even nuclei, at the start of a winter, will have more bees in the cold, outer shell, all making great efforts to stay alive by converting honey into heat-and accumulating more and more ‘waste water’ within the totality of the cluster. The centre being small, no movements in or out of the cluster centre can cope with the situation and, only cleansing flights can theoretically bring relief. When these are not possible, it seems that dysenteric conditions must come about, forcing bees to defecate in the hive, on combs.
Thirst and surplus rather than heat or cold seem to be a greater problem for wintering bees than we ever thought.
Mild spells occurring regularly throughout the Winter are of course providing the ideal solution for the “personal” problems of colonies and individual bees. After such flights, for water to cleanse themselves, the bees can settle down again and cluster normally, and peacefully once more. But not all climates and geographical locations can provide these chances on a regular basis, and not all colonies are of that “optimum strength” for best wintering results.
But bees know their beesiness and have a trick up their sleeves.
(Additional to prev. article)
Altmann, G. & Gontalsl-ti, H. (1961) Uber den
Wasscrhaushalt der Winterbienen.
Symposium Genet. Biol. llal. 12 : 308 –
Chauvin, R. (1968) (Editor) Traité de Biologie
de l‘Abeille. Musson er Cie, Paris, 2:
Furgala, Basil (1975), quoted by Grout, R.
(Editor). The Hive and the Honey Bee,
(Rev.Edition) Hamilton, lll. USA. pp 472-
Jeffree, E.P. & Allen, M.D. (1956) The influence of colony size and Nosema disease on the rate of population loss in Winter
I am looking for the sequel to this but to no avail as yet. I happen to know though that Bernard married up the excess of water to the brood rearing as a way of disposing of the water with out venturing out in the depths of Winter.