Until I read John's article (in BBKA News, May 2012), I felt guilty about my bees swarming. It's more of a problem in built up areas, but having a swamp and tolerant neighbours helps...
Bees swarm to reproduce and spread their genes. Healthy offspring
are best produced in optimum conditions of temperature and
nutrition and with a vigorous parent colony. However, like other
organisms, bees will be instinctively driven to reproduce more
when they are subjected to stress, danger and threatened survival.
Beekeepers are constantly being directed to control swarming
at all costs, whether to improve honey harvests or reduce nuisance
to neighbours. I have been wondering if a century of increasing
control over honey bees’ basic natural function has had an adverse
impact on the health of our bees. In this article I have considered
the bee’s reproductive process in a natural environment to see how
it benefits a colony, as well as the impact of swarm control
husbandry.
Swarm preparation phase
During springtime, a colony will build up rapidly, increasing its
stores, brood and adult bees. The colony maintains its brood nest
temperature at 35–36ºC, the optimum for rearing healthy brood.
By late April or early May a healthy colony will reach a state of
affluence, which will enable it to swarm.
Many beekeepers start swarm prevention
inspection in March at temperatures as low as
11ºC. This regular hive opening breaks open
propolis and wax seals; releases heat and
volatile compounds from the nest and disrupts
thousands of worker tasks. The result is a
stressed colony, forced to do unnecessary work
and with a brood temperature below the
optimum. This brood cooling can contribute to
European Foul Brood (EFB).1 The reduced nest
temperature also favours Varroa, which has an
optimum brood temperature of 33ºC; enabling
the colony to maintain a nest temperature of
35ºC works against Varroa.2
Varroa and other pathogens will thrive in
fatigued and weakened colonies. To keep
colonies alive beekeepers are using chemical
varroacides and medications. These substances,
even the organic acids and thymol, are toxic and harmful to bees.3,4
A colony will raise as many drones as it considers necessary.
Often beekeepers cull drones as unproductive honey consumers.
They also use drone brood as expendable varroa traps. This
reduction of the drone population has an adverse effect on the
quality of queen mating. It also consumes significant resources as
the colony strives to replace essential males in time for mating.
The swarm of bees has to find a new home, build comb, stock
it with stores and feed new brood. This requires bees of different
ages and gland development and will not include many old foragers.
An artificial swarm, which merely separates the queen and flying
bees from the house-bees and brood, risks having old spent bees
by the time new brood hatches out and requires feeding.
The colony raises a number of queen cells in specially
constructed round cells. Queen cells are given special treatment;
they are visited 10 times more often than worker bee cells during
the 3–5 day larval stage to ensure the optimum development of
new queens, which become almost double the weight of worker
bees. Queens raised artificially from 2-day-old larvae will receive
less nourishment and care.
In an unstressed colony the queen brood survival rate can be
as low as 53% from egg to adult; 33% in a stressed colony.5 The
colony appears to be weeding out substandard queens during
development. During artificial swarm manipulation, when we
destroy unwanted queen-cells, how do we know we have selected
the best two larvae? What are the chances they will fail or produce
substandard queens, resulting in a queen-less or a poorly
performing colony?
The swarm cluster
On leaving the nest, the swarm pours out of the hive or nest cavity
and mills around before settling in a cluster on a nearby bush, tree
or structure. Hundreds of forager bees become scouts and seek
cavities suitable for a new home. Instinctively they know what
constitutes a good cavity. After assessing a site, each scout returns
to the cluster and conveys its information to the cluster-bees in a
waggle dance. After considering different waggle
dances and checking the sites, the bees
eventually reach agreement about a site and the
scouts lead the swarm-bees to the new cavity.
This reconnaissance, communication and
consensus-reaching is an important part of the
bee’s metabolism, decision-making and
intelligence development. The new site is most
probably 300–500 metres from the home nest.6,7
This has the benefits of reducing
competition for forage as well as reducing the
risks of transfer of pathogens by drifting or
robbing. Fries and Camazine suggest8 that intercolony
transmission of pathogens by swarming
will result in a benign host-parasite relationship,
but the horizontal transfer of pathogens from
one colony to another by drifting, robbing and
comb exchange will result in more virulence.
The high colony density in large apiaries and the
‘splitting’ of colonies to achieve increase will
favour pathogen virulence.
Building the new nest
At the new site, bees make the cavity draught-proof with propolis
and start making wax. Bees construct honeycomb and forage for
stores; both are needed before brood rearing can commence. A
coating of antibacterial, antifungal propolis is applied to the cavity.
Temperatures of up to 40ºC are required to make comb9 and the
nest temperature will have to be maintained at 35ºC for brood
rearing. The swarm will be broodless during the nest building
period. Varroa will have no uncapped brood cells in which to hide,
and develop. They will be exposed to grooming by bees and fall to
the bottom of the cavity, far from the comb.
While the new nest is being constructed, stores collected
and brood started, the swarm is vulnerable to conditions of poor
weather, poor forage and predators. Seeley6 considers that about
three quarters of new swarms fail. Beekeepers reduce this
vulnerability by providing suitable nest sites and emergency
feeding to prevent starvation, often using sugar. Sugar is a poor
Swarming Bees are Healthy Bees
Swarm arrival. Photo by Bernhart Ruso.
BBKA News incorporating THE BRITISH BEE JOURNAL May 2012 17
substitute for nutritious honey10; brood
reared on poor nutrition will not
achieve optimum development and
immunocompetence will be reduced.
The home nest
The original nest is reduced by a queen,
about half of its adult bees and some of
the honey stores. It still has virgin queen
cells, developing brood, an extant nest
structure and good stocks of stores. It
is quite wealthy but will not be so if
beekeeper manipulation denudes it of
nurse bees and honey stores.
The first virgin queen could emerge eight days after the swarm
departure. Other brood will have hatched. The queen will take
time to mature and mate. Her egg laying may not commence for
three or four weeks after the swarm departs, depending on
weather conditions. Again a broodless period will work against
varroa. The collection of pollen and increased foraging will indicate
when brood rearing commences. Constant hive opening to check
for eggs is highly disruptive to a new and developing nest.
The first virgin queen may be allowed to kill her siblings, but if
the mother colony is strong and conditions are favourable, the
workers may protect some virgin queens so the colony can
produce secondary swarms, to spread its genes.
On the mating flights, colonies escort valuable virgin queens
providing a ‘herring shoal’ protection effect against bird predators.
Large escorts ensure successful returns whereas smaller escorts
from mini-colonies, favoured in artificial breeding, suffer queen
losses of some 33%.9 On the mating flight a vigorous queen will
require a good drone to catch her. Poor queens will be caught by
good males but can also be caught by poor drones increasing the
chances of low grade offspring.
Local bees will be genetically conditioned to the local
environment. In UK this can be cool, wet weather during the
swarming season. Local bees will be able to cope with inclement
weather and achieve successful mating when exotic bees from
warmer climates may not. The natural mating with up to 20 drones
will ensure genetic diversity, essential to species survival. Nature
will select for characteristics to enable survival in its environment
and against pathogens. These will not necessarily be the docility,
productivity and non-swarming sought by beekeepers.
Afterword
The entire swarming process brings
into play a huge array of diverse
behaviours affected by natural
selection. The colonies that survive the
dangerous adventure of swarming will,
on the whole, be the fittest. If we
short-circuit this fundamental
behavioural feature of the honey bee,
we reduce the opportunity for nature
to hone the fitness of the bee
population.
There is growing anecdotal and
scientific evidence11,12 that wild bees
are surviving and coping with varroa. It is clear to me, that the
ability to swarm naturally is a significant factor in their survival. I
believe we should be considering how we might better manage
swarming to make use of its colony health benefits; perhaps using
bait hives and informed, non-intrusive ‘reading’ of colony activity.13
This might reduce honey harvests, but there would be more bees.
Man can live without honey, but not without bees.
John Haverson, Hampshire BKA
References
1. Somerville D. European foulbrood and its control. Primefact
1000, 2010; p1–4. Available at http://www.dpi.nsw.gov.au/
__data/assets/pdf_file/0010/333388/European-foulbrood-andits-
control.pdf.
2. Kraus B, Velthius HHW. The impact of temperature gradients in
the brood nest of honeybees on the reproduction of Varroa jacobsoni,
Utrecht University archives, Netherlands, 2001.
3. Johnson RM, Ellis MD, Mullin CA, Frazier M. Pesticides and
honey bee toxicity — USA. Apidology, [online] 2010. Available
at http://entomology.unl.edu/faculty/ellispubs/Pesticides.pdf.
4. Mullin CA, Frazier M, Frazier JL et al. High levels of miticides
and agrochemicals in north American apiaries: Implication for
honeybee health. PLoS ONE [online] 2010. Available at
http://dx.plos.org/10.1371/journal.pone.0009754.
5. Winston ML. The biology of the honeybee, Harvard University
Press. Cambridge, 1987.
6. Seeley TD, Morse RA. Nest site selection by the honey bee,
Apis mellifera. Insectes Soc 1978; 25:323–37 .
7. Davis CF. The Honey bee inside and out, 2004. Available at
Beedata.com.
8. Fries I, Camazine S. Implications of horizontal and vertical
pathogen transmission for honey bee epidemiology. Apidologie
2001; 32: 199–214.
9. Tautz J. The buzz about bees; biology of a superorganism, Springer,
Heidelberg & Berlin, 2008.
10. Nicolson S, Thornburg RW. Nectar chemistry, In: Nectary and
nectar: A modern treatise. Pacini E, Nepi M, Nicolson S (eds), pp
215–263, Springer, 2007.
11. Seeley TD. Honey bees of the Arnot Forest: a population of
feral colonies persisting with Varroa destructor in the
northeastern United States. Apidologie, 2007; 38(1): 19–29.
12. Le Conte Y, de Vaublanc G, Crauser D et al. Honey bee colonies
that have survived Varroa destructor. Apidologie 2007; 38: 566–72.
13. Storch H. At the hive entrance. Observation handbook. How to
know what happens inside the hive by observation on the outside.
European Apicultural Editions, 1985. English translation available
at http://www.scribd.com/doc/54926139/At-the-Hive-Entrance-
Swarm hanging in a tree. Photo by scf courtesy of Vita-europe. H-Storch
Swarm moving up into brood box. Photo by John Haverson.
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